Merge pull request #57 from SecUSo/Sudoku-v3.0

Sudoku v3.0
- Added Darktheme
- Added Custom Sudokus
- Added Daily Sudoku
- Added Sudoku Sharing
- Several Bugfixes
Fixes #45, Fixes #24

app/build.gradle

@@ -11,8 +11,8 @@ android {
         applicationId "org.secuso.privacyfriendlysudoku"
         minSdkVersion 16
         targetSdkVersion 29
-        versionCode 8
+        versionCode 9
-        versionName "2.2.1"
+        versionName "3.0.0"
         vectorDrawables.useSupportLibrary = true
     }
     buildTypes {
@@ -25,16 +25,23 @@ android {
         sourceCompatibility JavaVersion.VERSION_1_8
         targetCompatibility JavaVersion.VERSION_1_8
     }
+
+    dataBinding {
+        enabled = true
+    }
 }
 
 dependencies {
     implementation fileTree(include: ['*.jar'], dir: 'libs')
+    implementation 'androidx.preference:preference:1.1.1'
     testImplementation 'junit:junit:4.12'
-    implementation 'androidx.core:core:1.2.0'
+    implementation 'androidx.core:core:1.3.2'
     implementation 'androidx.legacy:legacy-support-v4:1.0.0'
     implementation 'androidx.legacy:legacy-support-v13:1.0.0'
-    implementation 'androidx.appcompat:appcompat:1.1.0'
+    implementation 'androidx.appcompat:appcompat:1.2.0'
-    implementation 'com.google.android.material:material:1.1.0'
+    implementation 'com.google.android.material:material:1.2.1'
     implementation 'androidx.legacy:legacy-support-core-ui:1.0.0'
     implementation 'androidx.legacy:legacy-support-core-utils:1.0.0'
+    implementation 'androidx.constraintlayout:constraintlayout:2.0.1'
+
 }

app/src/main/AndroidManifest.xml

@@ -2,34 +2,39 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="org.secuso.privacyfriendlysudoku.ui.view">
 
-    <uses-permission android:name="android.permission.FOREGROUND_SERVICE"/>
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
 
     <application
+        android:name="org.secuso.privacyfriendlysudoku.SudokuApp"
         android:allowBackup="true"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:supportsRtl="true"
-        android:theme="@style/AppTheme"
+        android:theme="@style/AppTheme">
-        android:name="org.secuso.privacyfriendlysudoku.SudokuApp">
         <activity
             android:name="org.secuso.privacyfriendlysudoku.ui.SplashActivity"
             android:theme="@style/SplashTheme">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
-
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
         <activity
             android:name="org.secuso.privacyfriendlysudoku.ui.MainActivity"
             android:label="@string/app_name"
-            android:theme="@style/AppTheme.NoActionBar">
+            android:theme="@style/AppTheme.NoActionBar" />
-        </activity>
         <activity
             android:name="org.secuso.privacyfriendlysudoku.ui.TutorialActivity"
             android:label="@string/app_name"
-            android:theme="@style/AppTheme.NoActionBar">
+            android:theme="@style/AppTheme.NoActionBar" />
-        </activity>
+        <activity
+            android:name="org.secuso.privacyfriendlysudoku.ui.DailySudokuActivity"
+            android:label="@string/Sudoku"
+            android:theme="@style/AppTheme.NoActionBar" />
+        <activity
+            android:name="org.secuso.privacyfriendlysudoku.ui.CreateSudokuActivity"
+            android:label="@string/Sudoku"
+            android:theme="@style/AppTheme.NoActionBar" />
         <activity
             android:name="org.secuso.privacyfriendlysudoku.ui.SettingsActivity"
             android:label="@string/title_activity_settings"
@@ -37,7 +42,26 @@
         <activity
             android:name="org.secuso.privacyfriendlysudoku.ui.GameActivity"
             android:label="@string/title_activity_game_view"
-            android:theme="@style/AppTheme.NoActionBar" />
+            android:launchMode="singleTask"
+            android:theme="@style/AppTheme.NoActionBar">
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:scheme="sudoku" />
+            </intent-filter>
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data
+                    android:host="sudoku.secuso.org"
+                    android:scheme="http" />
+                <data
+                    android:host="sudoku.secuso.org"
+                    android:scheme="https" />
+            </intent-filter>
+        </activity>
         <activity android:name="org.secuso.privacyfriendlysudoku.ui.AboutActivity" />
         <activity android:name="org.secuso.privacyfriendlysudoku.ui.LoadGameActivity" />
         <activity

app/src/main/java/org/secuso/privacyfriendlysudoku/SudokuApp.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku;
 
 import android.app.Application;

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/GameController.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller;
 
 import android.content.Context;
@@ -6,7 +22,10 @@ import android.os.Handler;
 import android.os.Parcel;
 import android.os.Parcelable;
 
+import org.secuso.privacyfriendlysudoku.controller.database.DatabaseHelper;
+import org.secuso.privacyfriendlysudoku.controller.database.model.DailySudoku;
 import org.secuso.privacyfriendlysudoku.controller.helper.GameInfoContainer;
+import org.secuso.privacyfriendlysudoku.controller.qqwing.QQWing;
 import org.secuso.privacyfriendlysudoku.game.CellConflict;
 import org.secuso.privacyfriendlysudoku.game.CellConflictList;
 import org.secuso.privacyfriendlysudoku.game.GameBoard;
@@ -19,7 +38,10 @@ import org.secuso.privacyfriendlysudoku.game.listener.IHighlightChangedListener;
 import org.secuso.privacyfriendlysudoku.game.listener.IHintListener;
 import org.secuso.privacyfriendlysudoku.game.listener.IModelChangedListener;
 import org.secuso.privacyfriendlysudoku.game.listener.ITimerListener;
+import org.secuso.privacyfriendlysudoku.ui.GameActivity;
 
+import java.util.Calendar;
+import java.util.Date;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Timer;
@@ -32,6 +54,7 @@ import java.util.concurrent.atomic.AtomicBoolean;
 public class GameController implements IModelChangedListener, Parcelable {
 
     // General
+    public static final int DAILY_SUDOKU_ID = Integer.MAX_VALUE - 1;
     private SharedPreferences settings;
 
     // View
@@ -57,6 +80,7 @@ public class GameController implements IModelChangedListener, Parcelable {
     private GameType gameType;
     private GameDifficulty difficulty;
     private CellConflictList errorList = new CellConflictList();
+    private boolean gameIsCustom;
 
     // Undo Redo
     private UndoRedoManager undoRedoManager;
@@ -84,6 +108,7 @@ public class GameController implements IModelChangedListener, Parcelable {
     public GameController(GameType type, SharedPreferences pref, Context context) {
         this.context = context;
         this.gameBoard = new GameBoard(type);
+        this.gameIsCustom = false;
 
         setGameType(type);
         setSettings(pref);
@@ -95,6 +120,8 @@ public class GameController implements IModelChangedListener, Parcelable {
         return gameID;
     }
 
+    public boolean gameIsCustom() { return gameIsCustom; }
+
     public void loadNewLevel(GameType type, GameDifficulty difficulty) {
         NewLevelManager newLevelManager = NewLevelManager.getInstance(context, settings);
 
@@ -105,6 +132,23 @@ public class GameController implements IModelChangedListener, Parcelable {
         newLevelManager.checkAndRestock();
     }
 
+    public void loadNewDailySudokuLevel() {
+        NewLevelManager newLevelManager = NewLevelManager.getInstance(context, settings);
+
+        // generate the daily sudoku
+        int[] level = newLevelManager.loadDailySudoku();
+
+        // calculate the difficulty of the daily sudoku
+        QQWing difficultyCheck = new QQWing(GameType.Default_9x9, GameDifficulty.Unspecified);
+        difficultyCheck.setRecordHistory(true);
+        difficultyCheck.setPuzzle(level);
+        difficultyCheck.solve();
+
+        loadLevel(new GameInfoContainer(DAILY_SUDOKU_ID, difficultyCheck.getDifficulty(),
+                GameType.Default_9x9, level, null, null));
+
+    }
+
     public int getTime() {
         return time;
     }
@@ -117,6 +161,7 @@ public class GameController implements IModelChangedListener, Parcelable {
         this.difficulty = gic.getDifficulty();
         this.time = gic.getTimePlayed();
         this.usedHints = gic.getHintsUsed();
+        this.gameIsCustom = gic.isCustom();
 
         setGameType(gic.getGameType());
         this.gameBoard = new GameBoard(gic.getGameType());
@@ -305,7 +350,7 @@ public class GameController implements IModelChangedListener, Parcelable {
 
             SharedPreferences.Editor editor = settings.edit();
             // is anyone ever gonna play so many levels? :)
-            if(gameID == Integer.MAX_VALUE-1) {
+            if(gameID == DAILY_SUDOKU_ID - 1) {
                 editor.putInt("lastGameID", 1);
             } else {
                 editor.putInt("lastGameID", gameID);
@@ -318,6 +363,31 @@ public class GameController implements IModelChangedListener, Parcelable {
         fm.saveGameState(this);
     }
 
+    /**
+     * Save progress on the current daily sudoku
+     * @param context the context in which this method is called
+     */
+    public void saveDailySudoku(Context context) {
+        int amountOfCells = size * size;
+        int[] encodedBoard = new int[amountOfCells];
+
+        for (int i = 0; i < size; i++) {
+            for (int j = 0; j < size; j++) {
+                encodedBoard[i * size + j] = gameBoard.getCell(i, j).getValue();
+            }
+        }
+
+        // turn the current date into an id
+        Calendar currentDate = Calendar.getInstance();
+        int id = currentDate.get(Calendar.DAY_OF_MONTH) * 1000000
+                + (currentDate.get(Calendar.MONTH) + 1) * 10000 + currentDate.get(Calendar.YEAR);
+
+        // save the sudoku to the database using the previously calculated id
+        DatabaseHelper db = new DatabaseHelper(context);
+        DailySudoku dailySudoku = new DailySudoku(id, difficulty, gameType, encodedBoard, usedHints, GameActivity.timeToString(time));
+        db.addDailySudoku(dailySudoku);
+    }
+
     public void deleteGame(Context context) {
         if(gameID == 0) {
             throw new IllegalArgumentException("GameID may not be 0.");
@@ -414,6 +484,7 @@ public class GameController implements IModelChangedListener, Parcelable {
         return gameBoard.toString();
     }
 
+    public String getCodeOfField() { return gameBoard.transformToCode(); }
 
 
 

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/GameStateManager.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller;
 
 import android.content.Context;
@@ -20,6 +36,7 @@ public class GameStateManager {
 
     Context context;
     private SharedPreferences settings;
+    private boolean includesDaily;
 
     private static String FILE_EXTENSION = ".txt";
     private static String SAVE_PREFIX = "save_";
@@ -87,6 +104,15 @@ public class GameStateManager {
                     gic.parseSetValues(values[i++]);
                     gic.parseNotes(values[i++]);
                     gic.parseHintsUsed(values[i++]);
+
+                    if (values.length > i) {
+                        gic.setCustom(true);
+                    }
+
+                    if (gic.getID() == GameController.DAILY_SUDOKU_ID) {
+                        includesDaily = true;
+                    }
+
                 } catch(IllegalArgumentException e) {
                     file.delete();
                     continue;
@@ -108,7 +134,7 @@ public class GameStateManager {
         LinkedList<GameInfoContainer> removeList = new LinkedList<>();
 
         for(int i = 0; i < list.size(); i++) {
-            if(i >= MAX_NUM_OF_SAVED_GAMES) {
+            if((i >= MAX_NUM_OF_SAVED_GAMES && !includesDaily) || i > MAX_NUM_OF_SAVED_GAMES) {
                 deleteGameStateFile(list.get(i));
                 removeList.add(list.get(i));
             }

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/GeneratorService.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller;
 
 import android.app.IntentService;

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/Highscore.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/NewLevelManager.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller;
 
 import android.content.Context;
@@ -15,6 +31,9 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
+import java.util.Date;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Random;
@@ -37,6 +56,10 @@ public class NewLevelManager {
     public static int PRE_SAVES_MIN = 3;
     public static int PRE_SAVES_MAX = 10;
 
+    private final double CHALLENGE_GENERATION_PROBABILITY = 0.25;
+    private final int CHALLENGE_ITERATIONS = 4;
+
+
     public static NewLevelManager getInstance(Context context, SharedPreferences settings) {
         if(instance == null) {
             instance = new NewLevelManager(context, settings);
@@ -75,6 +98,16 @@ public class NewLevelManager {
         return false;
     }
 
+    public int[] loadDailySudoku() {
+        // create a seed from the current date
+        DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
+        String toHash = "Sudoku/.PrivacyFriendly/." + dateFormat.format(new Date());
+        QQWingController controller = new QQWingController();
+
+        // generate new sudoku using the previously computed seed
+        return controller.generateFromSeed(toHash.hashCode(), CHALLENGE_GENERATION_PROBABILITY, CHALLENGE_ITERATIONS);
+    }
+
     public int[] loadLevel(GameType type, GameDifficulty diff) {
         Level level = dbHelper.getLevel(diff, type);
         dbHelper.deleteLevel(level.getId());

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/QQWingController.java

@@ -1,9 +1,26 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller;
 
 import android.os.Parcelable;
 import android.util.Log;
 
 import java.util.LinkedList;
+import java.util.Random;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.Date;
@@ -53,6 +70,49 @@ public class QQWingController {
         return generated;
     }
 
+    /**
+     * Generate a new sudoku based on a given seed regardless of outcome difficulty
+     * @param seed the seed based on which the sudoku should be calculated
+     * @return the generated sudoku
+     */
+    public int[] generateFromSeed(int seed) {
+        return generateFromSeed(seed, 1, 1);
+    }
+
+    /**
+     * Generate a new sudoku based on a given seed, but only accept challenge sudokus with a certain probability
+     * @param seed the seed based on which the sudoku should be calculated
+     * @param challengePermission the probability with which a challenge sudoku is accepted upon calculation
+     * @param challengeIterations the amount of times a challenge sudoku can be rejected in a row before being
+     *                            accepted with a probability of 100%
+     * @return the generated sudoku
+     */
+    public int[] generateFromSeed(int seed, double challengePermission, int challengeIterations) {
+        generated.clear();
+        QQWing generator = new QQWing(GameType.Default_9x9, GameDifficulty.Unspecified);
+        boolean continueSearch = true;
+        Random random = new Random(seed);
+        int seedFactor = 2;
+
+        while(continueSearch && challengeIterations > 0) {
+            seed *= seedFactor;
+            generator.setRandom(seed);
+            generator.setRecordHistory(true);
+            generator.generatePuzzle();
+
+            if (generator.getDifficulty() != GameDifficulty.Challenge || random.nextDouble() < challengePermission) {
+                continueSearch = false;
+            } else {
+                challengeIterations--;
+            }
+        }
+
+        generated.add(generator.getPuzzle());
+        opts.gameType = GameType.Default_9x9;
+        opts.gameDifficulty = generator.getDifficulty();
+        return generated.poll();
+    }
+
     public int[] solve(GameBoard gameBoard) {
 
         level = new int[gameBoard.getSize()*gameBoard.getSize()];
@@ -200,6 +260,10 @@ public class QQWingController {
         }
     }
 
+    public boolean isImpossible() {
+        return solveImpossible;
+    }
+
     private static class QQWingOptions {
         // defaults for options
         boolean needNow = false;

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/SaveLoadStatistics.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller;
 
 import android.content.Context;
@@ -204,12 +220,12 @@ public class SaveLoadStatistics implements ITimerListener, IHintListener {
 
     @Override
     public void onTick(int time) {
-        incTime(gc.getDifficulty(), gc.getGameType());
+        if (!gc.gameIsCustom()) incTime(gc.getDifficulty(), gc.getGameType());
         //gc.getUsedHints();
     }
 
     @Override
     public void onHintUsed() {
-        incHints(gc.getDifficulty(),gc.getGameType());
+        if (!gc.gameIsCustom()) incHints(gc.getDifficulty(),gc.getGameType());
     }
 }

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/Symbol.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/UndoRedoManager.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller;
 
 import android.os.Parcel;

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/database/DatabaseHelper.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller.database;
 
 import android.content.ContentValues;
@@ -6,7 +22,10 @@ import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteOpenHelper;
 
+import org.secuso.privacyfriendlysudoku.controller.database.columns.DailySudokuColumns;
 import org.secuso.privacyfriendlysudoku.controller.database.columns.LevelColumns;
+import org.secuso.privacyfriendlysudoku.controller.database.migration.MigrationUtil;
+import org.secuso.privacyfriendlysudoku.controller.database.model.DailySudoku;
 import org.secuso.privacyfriendlysudoku.controller.database.model.Level;
 import org.secuso.privacyfriendlysudoku.game.GameDifficulty;
 import org.secuso.privacyfriendlysudoku.game.GameType;
@@ -18,7 +37,7 @@ import java.util.List;
 
 public class DatabaseHelper extends SQLiteOpenHelper {
 
-    public static final int DATABASE_VERSION = 1;
+    public static final int DATABASE_VERSION = 2;
     public static final String DATABASE_NAME = "Database.db";
 
     public DatabaseHelper(Context context) {
@@ -28,11 +47,16 @@ public class DatabaseHelper extends SQLiteOpenHelper {
     @Override
     public void onCreate(SQLiteDatabase db) {
         db.execSQL(LevelColumns.SQL_CREATE_ENTRIES);
+        db.execSQL(DailySudokuColumns.SQL_CREATE_ENTRIES);
     }
 
     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
-        db.execSQL(LevelColumns.SQL_DELETE_ENTRIES);
+        // fallback to destructive migration if no migration could be executed
-        onCreate(db);
+        if(!MigrationUtil.executeMigration(db, oldVersion, newVersion)) {
+            db.execSQL(LevelColumns.SQL_DELETE_ENTRIES);
+            db.execSQL(DailySudokuColumns.SQL_DELETE_ENTRIES);
+            onCreate(db);
+        }
     }
 
     public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
@@ -80,6 +104,39 @@ public class DatabaseHelper extends SQLiteOpenHelper {
         return levelList.get(0);
     }
 
+    /**
+     * Returns a list of all the daily sudokus that have been solved and thus saved to the database
+     * @return a list of all the daily sudokus that have been solved so far
+     */
+    public synchronized List<DailySudoku> getDailySudokus() {
+        List<DailySudoku> dailySudokuList = new LinkedList<>();
+        SQLiteDatabase database = getWritableDatabase();
+
+        // order results from most to least recent
+        String order = DailySudokuColumns._ID + " DESC";
+
+        // How you want the results sorted in the resulting Cursor
+        Cursor c = database.query(
+                DailySudokuColumns.TABLE_NAME,         // The table to query
+                DailySudokuColumns.PROJECTION,                // The columns to return
+                null,                                // select all rows
+                null,                            // select all rows
+                null,                                     // don't group the rows
+                null,                                     // don't filter by row groups
+                order                                    // The sort order
+        );
+
+        if (c != null) {
+            while(c.moveToNext()) {
+                dailySudokuList.add(DailySudokuColumns.getLevel(c));
+            }
+        }
+
+        c.close();
+        return dailySudokuList;
+
+    }
+
     public synchronized void deleteLevel(int id) {
         SQLiteDatabase database = getWritableDatabase();
 
@@ -93,5 +150,15 @@ public class DatabaseHelper extends SQLiteOpenHelper {
         SQLiteDatabase database = getWritableDatabase();
         return database.insert(LevelColumns.TABLE_NAME, null, LevelColumns.getValues(level));
     }
+
+    /**
+     * Adds a new daily sudoku to the database
+     * @param ds the daily sudoku which is to be added to the database
+     * @return the row id of the newly inserted sudoku (or -1 if an error occurred)
+     */
+    public synchronized long addDailySudoku(DailySudoku ds) {
+        SQLiteDatabase database = getWritableDatabase();
+        return database.insert(DailySudokuColumns.TABLE_NAME, null, DailySudokuColumns.getValues(ds));
+    }
 }
 

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/database/columns/DailySudokuColumns.java

@@ -0,0 +1,89 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.secuso.privacyfriendlysudoku.controller.database.columns;
+
+import android.content.ContentValues;
+import android.database.Cursor;
+import android.provider.BaseColumns;
+
+import org.secuso.privacyfriendlysudoku.controller.database.model.DailySudoku;
+import org.secuso.privacyfriendlysudoku.controller.database.model.Level;
+
+
+/**
+ * Defines a database schema for saving daily sudokus
+ */
+public class DailySudokuColumns extends LevelColumns {
+
+    public static final String TABLE_NAME = "ds_levels";
+
+    public static final String HINTS_USED = "ds_hints_used";
+    public static final String TIME_NEEDED = "ds_time_needed";
+    public static final String[] PROJECTION = {
+            _ID,
+            DIFFICULTY,
+            GAMETYPE,
+            PUZZLE,
+            HINTS_USED,
+            TIME_NEEDED
+    };
+
+    private static final String TEXT_TYPE = " TEXT ";
+    private static final String INTEGER_TYPE = " INTEGER ";
+    private static final String TIME_TYPE = " TIME (0) ";
+    private static final String COMMA_SEP = ",";
+
+    public static String SQL_CREATE_ENTRIES =
+            "CREATE TABLE " + TABLE_NAME + " (" +
+                    _ID         + INTEGER_TYPE + " PRIMARY KEY" + COMMA_SEP +
+                    DIFFICULTY        + TEXT_TYPE + COMMA_SEP +
+                    GAMETYPE  + TEXT_TYPE + COMMA_SEP +
+                    PUZZLE     + TEXT_TYPE + COMMA_SEP +
+                    HINTS_USED  + INTEGER_TYPE + COMMA_SEP +
+                    TIME_NEEDED + TIME_TYPE + " )";
+
+    public static String SQL_DELETE_ENTRIES =
+            "DROP TABLE IF EXISTS " + TABLE_NAME;
+
+
+    /**
+     * Create a new DailySudoku object using the data stored in a specific database row
+     * @param c the cursor pointing to the row whose data should be used
+     * @return the DailySudoku object created using the data from the database row
+     */
+    public static DailySudoku getLevel(Cursor c) {
+        Level level = LevelColumns.getLevel(c);
+        int hintsUsed = c.getInt(c.getColumnIndexOrThrow(HINTS_USED));
+        String timeNeeded = c.getString(c.getColumnIndexOrThrow(TIME_NEEDED));
+        return new DailySudoku(level.getId(), level.getDifficulty(), level.getGameType(), level.getPuzzle(), hintsUsed, timeNeeded);
+    }
+
+    /**
+     * Given a specific DailySudoku instance, extracts all relevant parameters and saves them to a ContentValues object
+     * @param record the DailySudoku instance whose parameters should be extracted
+     * @return the ContentValues instance containing the extracted parameters
+     */
+    public static ContentValues getValues(DailySudoku record) {
+        ContentValues result = LevelColumns.getValues(record);
+        result.put(HINTS_USED, record.getHintsUsed());
+        result.put(TIME_NEEDED, record.getTimeNeeded());
+
+        return result;
+    }
+
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/database/columns/LevelColumns.java

@@ -1,3 +1,20 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+
 package org.secuso.privacyfriendlysudoku.controller.database.columns;
 
 import android.content.ContentValues;

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/database/migration/Migration.java

@@ -0,0 +1,35 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.secuso.privacyfriendlysudoku.controller.database.migration;
+
+import android.database.sqlite.SQLiteDatabase;
+
+/**
+ * Similar idea to room migration class.
+ * @author Christopher Beckmann
+ */
+public abstract class Migration {
+    int from = 0;
+    int to = 0;
+
+    public Migration(int from, int to) {
+        this.from = from;
+        this.to = to;
+    }
+
+    public abstract void migrate(SQLiteDatabase db);
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/database/migration/MigrationUtil.java

@@ -0,0 +1,52 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.secuso.privacyfriendlysudoku.controller.database.migration;
+
+import android.database.sqlite.SQLiteDatabase;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.secuso.privacyfriendlysudoku.controller.database.columns.DailySudokuColumns.SQL_CREATE_ENTRIES;
+
+/**
+ * @author Christopher Beckmann
+ */
+public class MigrationUtil {
+
+    public static List<Migration> migrations = Arrays.asList(
+            new Migration(1,2) {
+                @Override
+                public void migrate(SQLiteDatabase db) {
+                    db.execSQL(SQL_CREATE_ENTRIES);
+                }
+            }
+    );
+
+    //TODO: for now just try to find the desired migration from the list.
+    // -> When more migrations are added, a chain could be found, e.g. 1->2->3
+    public static boolean executeMigration(SQLiteDatabase db, int from, int to) {
+        for(Migration m : migrations) {
+            if(m.from == from && m.to == to) {
+                m.migrate(db);
+                return true;
+            }
+        }
+        return false;
+    }
+
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/database/model/DailySudoku.java

@@ -0,0 +1,86 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.secuso.privacyfriendlysudoku.controller.database.model;
+
+import org.secuso.privacyfriendlysudoku.game.GameDifficulty;
+import org.secuso.privacyfriendlysudoku.game.GameType;
+
+/**
+ * Models the content of a single row of the daily sudoku database
+ */
+public class DailySudoku extends Level {
+    private int hintsUsed;
+    private String timeNeeded;
+
+    public DailySudoku(int id, GameDifficulty gameDifficulty, GameType gameType, int[] puzzle, int hintsUsed, String timeNeeded) {
+        super(id, gameDifficulty, gameType, puzzle);
+        this.hintsUsed = hintsUsed;
+        this.timeNeeded = timeNeeded;
+    }
+
+    /**
+     * Return the amount of hints the user needed to solve this sudoku
+     * @return the amount of hints the user needed to solve this sudoku
+     */
+    public int getHintsUsed() {
+        return hintsUsed;
+    }
+
+    /**
+     * Set a new value for the hintsUsed attribute of this daily sudoku
+     * @param hintsUsed the new value for the hintsUsed attribute
+     */
+    public void setHintsUsed(int hintsUsed) {
+        this.hintsUsed = hintsUsed;
+    }
+
+    /**
+     * Return the time the user needed to solve this sudoku as a string
+     * @return the time the user needed to solve this sudoku as a string
+     */
+    public String getTimeNeeded() {
+        return timeNeeded;
+    }
+
+    /**
+     * Return the time the user needed to solve this sudoku in seconds
+     * @return the time the user needed to solve this sudoku in seconds (or 0 if the timeNeeded parameter
+     * does not have the right format)
+     */
+    public int getTimeNeededInSeconds() {
+        if (timeNeeded.matches("[0-9]{2}:[0-5][0-9]:[0-5][0-9]")) {
+            String[] timeInstances = timeNeeded.split(":");
+            int hourIndex = 0;
+            int minuteIndex = 1;
+            int secondIndex = 2;
+
+            int minutes = Integer.parseInt(timeInstances[hourIndex]) * 60 + Integer.parseInt(timeInstances[minuteIndex]);
+            return minutes * 60 + Integer.parseInt(timeInstances[secondIndex]);
+           }
+
+        return 0;
+    }
+
+    /**
+     * Set a new value for the timeNeeded attribute of this daily sudoku
+     * @param timeNeeded the new value for the timeNeeded attribute
+     */
+    public void setTimeNeeded(String timeNeeded) {
+        this.timeNeeded = timeNeeded;
+    }
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/database/model/Level.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller.database.model;
 
 import org.secuso.privacyfriendlysudoku.controller.Symbol;

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/helper/GameInfoContainer.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller.helper;
 
 import android.util.Log;
@@ -25,6 +41,7 @@ public class GameInfoContainer {
     int[] setValues;
     boolean[][] setNotes;
     int hintsUsed;
+    boolean isCustom;
 
     public GameInfoContainer() {}
     public GameInfoContainer(int ID, GameDifficulty difficulty, GameType gameType, int[] fixedValues, int[] setValues, boolean[][] setNotes) {
@@ -40,17 +57,19 @@ public class GameInfoContainer {
         this.setValues = setValues;
         this.setNotes = setNotes;
         this.hintsUsed = hintsUsed;
+        isCustom = false;
     }
 
     public void setID(int ID) {
         this.ID = ID;
     }
 
+    public void setCustom (boolean isCustom) { this.isCustom = isCustom; }
+
+    public boolean isCustom () { return  isCustom; }
+
     public void parseGameType(String s) {
         gameType = Enum.valueOf(GameType.class, s);
-        if(gameType == null) {
-            throw new IllegalArgumentException("GameInfoContainer: gameType could not be set.");
-        }
     }
 
     public int getTimePlayed() {
@@ -63,7 +82,7 @@ public class GameInfoContainer {
 
     public void parseTime(String s) {
         try {
-            this.timePlayed = Integer.valueOf(s);
+            this.timePlayed = Integer.parseInt(s);
         } catch(NumberFormatException e) {
             throw new IllegalArgumentException("GameInfoContainer: Can not parse time.", e);
         }
@@ -71,7 +90,7 @@ public class GameInfoContainer {
 
     public void parseHintsUsed(String s) {
         try {
-            this.hintsUsed = Integer.valueOf(s);
+            this.hintsUsed = Integer.parseInt(s);
         } catch(NumberFormatException e) {
             throw new IllegalArgumentException("GameInfoContainer: Can not parse hints used.", e);
         }
@@ -79,7 +98,7 @@ public class GameInfoContainer {
 
     public void parseDate(String s) {
         try {
-            this.lastTimePlayed = new Date(Long.valueOf(s));
+            this.lastTimePlayed = new Date(Long.parseLong(s));
         } catch(NumberFormatException e) {
             throw new IllegalArgumentException("GameInfoContainer: LastTimePlayed Date can not be extracted.", e);
         }
@@ -87,9 +106,6 @@ public class GameInfoContainer {
 
     public void parseDifficulty(String s) {
         difficulty = Enum.valueOf(GameDifficulty.class, s);
-        if(difficulty == null) {
-            throw new IllegalArgumentException("GameInfoContainer: difficulty could not be set.");
-        }
     }
 
     public void parseFixedValues(String s){
@@ -104,6 +120,11 @@ public class GameInfoContainer {
         fixedValues = new int[s.length()];
         for(int i = 0; i < s.length(); i++) {
                fixedValues[i] = Symbol.getValue(Symbol.SaveFormat, String.valueOf(s.charAt(i)))+1;
+               if (gameType != GameType.Unspecified && gameType != null) {
+                   if (fixedValues[i] < 0 || fixedValues[i] > gameType.getSize()) {
+                       throw new IllegalArgumentException("Fixed values must each be smaller than " + gameType.getSize() + ".");
+                   }
+               }
         }
     }
 
@@ -128,7 +149,7 @@ public class GameInfoContainer {
         int size = gameType.getSize();
         int sq = size*size;
 
-        if(gameType != GameType.Unspecified && gameType != null) {
+        if(gameType != GameType.Unspecified) {
             if(strings.length != sq) {
                 throw new IllegalArgumentException("The string array must have "+sq+" entries.");
             }
@@ -174,6 +195,7 @@ public class GameInfoContainer {
     public static String getGameInfo(GameController controller) {
         StringBuilder sb = new StringBuilder();
         Date today = new Date();
+        boolean custom = controller.gameIsCustom();
 
         sb.append(controller.getGameType().name());
         sb.append("/");
@@ -191,6 +213,12 @@ public class GameInfoContainer {
         sb.append("/");
         sb.append(controller.getUsedHints());
 
+        // add additional information to custom sudokus to ensure they can be distinguished from 'regular' sudokus
+        if (custom) {
+            sb.append("/");
+            sb.append(custom);
+        }
+
         String result = sb.toString();
 
         Log.d("getGameInfo", result);

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/helper/HighscoreInfoContainer.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.controller.helper;
 
 import org.secuso.privacyfriendlysudoku.controller.GameController;

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/qqwing/Action.java

@@ -5,7 +5,7 @@
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
+ * the Free Software Foundation; either version 3 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/qqwing/LogItem.java

@@ -5,7 +5,7 @@
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
+ * the Free Software Foundation; either version 3 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/qqwing/LogType.java

@@ -5,7 +5,7 @@
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
+ * the Free Software Foundation; either version 3 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/qqwing/PrintStyle.java

@@ -5,7 +5,7 @@
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
+ * the Free Software Foundation; either version 3 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/qqwing/QQWing.java

@@ -7,7 +7,7 @@
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
+ * the Free Software Foundation; either version 3 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
@@ -199,6 +199,10 @@ public class QQWing {
 		return reset();
 	}
 
+	public void setRandom(int seed) {
+		random = new Random(seed);
+	}
+
 	/**
 	 * Reset the board to its initial state with only the givens. This method
 	 * clears any solution, resets statistics, and clears any history messages.

app/src/main/java/org/secuso/privacyfriendlysudoku/controller/qqwing/Symmetry.java

@@ -5,7 +5,7 @@
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
+ * the Free Software Foundation; either version 3 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,

app/src/main/java/org/secuso/privacyfriendlysudoku/game/CellConflict.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game;
 
 import android.os.Parcel;

app/src/main/java/org/secuso/privacyfriendlysudoku/game/CellConflictList.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game;
 
 import java.util.ArrayList;

app/src/main/java/org/secuso/privacyfriendlysudoku/game/GameBoard.java

@@ -1,8 +1,25 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game;
 
 import android.os.Parcel;
 import android.os.Parcelable;
 
+import org.secuso.privacyfriendlysudoku.controller.Symbol;
 import org.secuso.privacyfriendlysudoku.game.listener.IModelChangedListener;
 
 import java.util.LinkedList;
@@ -214,6 +231,20 @@ public class GameBoard implements Cloneable, Parcelable {
         return sb.toString();
     }
 
+    public String transformToCode () {
+        StringBuilder sb = new StringBuilder();
+        for(int i = 0; i < field.length; i++) {
+            for (int j = 0; j < field[0].length; j++) {
+                if (field[i][j].getValue() == 0) {
+                    sb.append(0);
+                } else {
+                    sb.append(Symbol.getSymbol(Symbol.SaveFormat, field[i][j].getValue()-1));
+                }
+            }
+        }
+        return sb.toString();
+    }
+
     public boolean isFilled() {
         return actionOnCells(new ICellAction<Boolean>() {
             @Override

app/src/main/java/org/secuso/privacyfriendlysudoku/game/GameCell.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game;
 
 import android.os.Parcel;

app/src/main/java/org/secuso/privacyfriendlysudoku/game/GameDifficulty.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game;
 
 import android.os.Parcel;

app/src/main/java/org/secuso/privacyfriendlysudoku/game/GameSettings.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/game/GameStatus.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/game/GameType.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game;
 
 import android.os.Parcel;

app/src/main/java/org/secuso/privacyfriendlysudoku/game/ICellAction.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/game/listener/IGameErrorListener.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game.listener;
 
 import org.secuso.privacyfriendlysudoku.game.CellConflict;

app/src/main/java/org/secuso/privacyfriendlysudoku/game/listener/IGameSolvedListener.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game.listener;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/game/listener/IHighlightChangedListener.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game.listener;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/game/listener/IHintListener.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game.listener;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/game/listener/IModelChangedListener.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game.listener;
 
 import org.secuso.privacyfriendlysudoku.game.GameCell;

app/src/main/java/org/secuso/privacyfriendlysudoku/game/listener/ITimerListener.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.game.listener;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/AboutActivity.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
 import android.graphics.Color;
@@ -11,6 +27,10 @@ import android.widget.TextView;
 import org.secuso.privacyfriendlysudoku.ui.view.BuildConfig;
 import org.secuso.privacyfriendlysudoku.ui.view.R;
 
+/**
+ * The AboutActivity is extended by the BaseActivity and is responsible for the content of the AboutActivity.
+ */
+
 public class AboutActivity extends BaseActivity {
 
     @Override

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/AppCompatPreferenceActivity.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
 import android.content.res.Configuration;

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/BaseActivity.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
 import android.os.Bundle;

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/CreateSudokuActivity.java

@@ -0,0 +1,294 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.secuso.privacyfriendlysudoku.ui;
+
+import android.content.Context;
+import android.content.Intent;
+import android.content.SharedPreferences;
+import android.content.res.Configuration;
+import android.graphics.Point;
+import android.net.Uri;
+import android.os.Bundle;
+import android.preference.PreferenceManager;
+import android.view.View;
+import android.view.WindowManager;
+import android.widget.LinearLayout;
+import android.widget.TextView;
+import android.widget.Toast;
+
+import androidx.appcompat.app.AppCompatDelegate;
+import androidx.appcompat.widget.Toolbar;
+
+import org.secuso.privacyfriendlysudoku.controller.GameController;
+import org.secuso.privacyfriendlysudoku.controller.Symbol;
+import org.secuso.privacyfriendlysudoku.controller.helper.GameInfoContainer;
+import org.secuso.privacyfriendlysudoku.controller.qqwing.QQWing;
+import org.secuso.privacyfriendlysudoku.game.GameDifficulty;
+import org.secuso.privacyfriendlysudoku.game.GameType;
+import org.secuso.privacyfriendlysudoku.ui.listener.IFinalizeDialogFragmentListener;
+import org.secuso.privacyfriendlysudoku.ui.listener.IImportDialogFragmentListener;
+import org.secuso.privacyfriendlysudoku.ui.view.CreateSudokuSpecialButtonLayout;
+import org.secuso.privacyfriendlysudoku.ui.view.R;
+import org.secuso.privacyfriendlysudoku.ui.view.SudokuFieldLayout;
+import org.secuso.privacyfriendlysudoku.ui.view.SudokuKeyboardLayout;
+
+/**
+ * The CreateSudokuActivity is an activity which extends the BaseActivity and implements the
+ * IFinalizeDialogFragementListener. It is used to create custom sudokus, which are passed to the
+ * GameActivity afterwards.
+ */
+public class CreateSudokuActivity extends BaseActivity implements IFinalizeDialogFragmentListener, IImportDialogFragmentListener {
+
+    GameController gameController;
+    SharedPreferences sharedPref;
+    SudokuFieldLayout layout;
+    SudokuKeyboardLayout keyboard;
+    CreateSudokuSpecialButtonLayout specialButtonLayout;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        sharedPref = PreferenceManager.getDefaultSharedPreferences(this);
+
+        if (sharedPref.getBoolean("pref_keep_screen_on", true)) {
+            getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
+        }
+
+        if(savedInstanceState == null) {
+
+            gameController = new GameController(sharedPref, getApplicationContext());
+
+            Bundle extras = getIntent().getExtras();
+            GameType gameType = GameType.valueOf(extras.getString("gameType", GameType.Default_9x9.name()));
+            int sectionSize = gameType.getSize();
+            int boardSize = sectionSize * sectionSize;
+
+            GameInfoContainer container = new GameInfoContainer(0, GameDifficulty.Moderate,
+                    gameType, new int[boardSize], new int[boardSize], new boolean[boardSize][sectionSize]);
+            gameController.loadLevel(container);
+        } else {
+            gameController = savedInstanceState.getParcelable("gameController");
+            if(gameController != null) {
+                gameController.removeAllListeners();
+                gameController.setContextAndSettings(getApplicationContext(), sharedPref);
+            }
+        }
+
+        setUpLayout();
+    }
+
+    private void setUpLayout() {
+
+        setContentView(R.layout.activity_create_sudoku);
+
+        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
+        setSupportActionBar(toolbar);
+        getSupportActionBar().setTitle(getString(gameController.getGameType().getStringResID()));
+        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
+
+        layout = (SudokuFieldLayout)findViewById(R.id.sudokuLayout);
+        layout.setSettingsAndGame(sharedPref, gameController);
+
+        keyboard = (SudokuKeyboardLayout) findViewById(R.id.sudokuKeyboardLayout);
+        keyboard.removeAllViews();
+        keyboard.setGameController(gameController);
+        Point p = new Point();
+        getWindowManager().getDefaultDisplay().getSize(p);
+
+        int orientation = getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT ?
+                LinearLayout.HORIZONTAL : LinearLayout.VERTICAL;
+
+        keyboard.setKeyBoard(gameController.getSize(), p.x,layout.getHeight()-p.y, orientation);
+
+        specialButtonLayout = (CreateSudokuSpecialButtonLayout) findViewById(R.id.createSudokuLayout);
+        specialButtonLayout.setButtons(p.x, gameController, keyboard, getFragmentManager(), orientation,
+                CreateSudokuActivity.this, this, this);
+
+        gameController.notifyHighlightChangedListeners();
+    }
+
+    @Override
+    public boolean onSupportNavigateUp() {
+        onBackPressed();
+        return true;
+    }
+
+    @Override
+    public void onResume(){
+        super.onResume();
+
+        View mainContent = findViewById(R.id.main_content);
+        if (mainContent != null) {
+            mainContent.animate().alpha(1).setDuration(MAIN_CONTENT_FADEOUT_DURATION);
+        }
+
+        SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(this);
+        Symbol s;
+        try {
+            s = Symbol.valueOf(sharedPref.getString("pref_symbols", Symbol.Default.name()));
+        } catch(IllegalArgumentException e) {
+            s = Symbol.Default;
+        }
+        layout.setSymbols(s);
+        keyboard.setSymbols(s);
+    }
+
+    @Override
+    public void onBackPressed() {
+        finish();
+        super.onBackPressed();
+    }
+
+    /**
+     * Verifies an encoded sudoku board by testing whether or not it is uniquely solvable
+     * @param gameType the type of the encoded sudoku
+     * @param boardContent the encoded sudoku
+     * @return whether or not the sudoku is uniquely solvable
+     */
+    public static boolean verify(GameType gameType, String boardContent) {
+        int boardSize = gameType.getSize() * gameType.getSize();
+
+        GameInfoContainer container = new GameInfoContainer(0, GameDifficulty.Unspecified,
+                gameType, new int [boardSize], new int [boardSize], new boolean [boardSize][gameType.getSize()]);
+
+        try {
+            container.parseFixedValues(boardContent);
+        } catch (IllegalArgumentException e) {
+            return false;
+        }
+
+        QQWing verifier = new QQWing(gameType, GameDifficulty.Unspecified);
+        verifier.setRecordHistory(true);
+        verifier.setPuzzle(container.getFixedValues());
+        verifier.solve();
+
+        return verifier.hasUniqueSolution();
+    }
+
+    /**
+     * If the positive button of the FinalizeDialog is clicked, verify the sudoku. Immediately pass
+     * it to the GameActivity, if the verification process is successful, and do nothing apart from
+     * notifying the user if not.
+     * Implements the onFinalizeDialogPositiveClick() method of the IFinalizeDialogFragmentListener
+     * interface.
+     */
+    public void onFinalizeDialogPositiveClick() {
+        Toast.makeText(CreateSudokuActivity.this, R.string.verify_custom_sudoku_process_toast, Toast.LENGTH_SHORT).show();
+        String boardContent = gameController.getCodeOfField();
+        boolean distinctlySolvable = verify(gameController.getGameType(), boardContent);
+
+        if(distinctlySolvable) {
+            Toast.makeText(CreateSudokuActivity.this, R.string.finished_verifying_custom_sudoku_toast, Toast.LENGTH_LONG).show();
+            final Intent intent = new Intent(this, GameActivity.class);
+
+            /*
+            Since the GameActivity expects the links of imported sudokus to start with an url scheme,
+            add one to the start of the encoded board
+             */
+            String scheme = GameActivity.validUris.size() > 0 ? GameActivity.validUris.get(0).getScheme()
+                    + "://" + GameActivity.validUris.get(0).getHost() : "";
+            if (!scheme.equals("") && !scheme.endsWith("/")) scheme = scheme + "/";
+
+            intent.setData(Uri.parse(scheme + boardContent));
+            intent.putExtra("isCustom", true);
+            startActivity(intent);
+            finish();
+        } else {
+            Toast.makeText(CreateSudokuActivity.this, R.string.failed_to_verify_custom_sudoku_toast, Toast.LENGTH_LONG).show();
+        }
+
+    }
+    public void onImportDialogPositiveClick(String input) {
+        String inputSudoku = null;
+        String prefix;
+        StringBuilder errorMessage = new StringBuilder();
+
+        /*  remove the present prefix, or, if the input contains none of the valid prefixes, notify the user
+         that their input is not valid */
+        for (int i = 0; i < GameActivity.validUris.size(); i++) {
+            prefix = GameActivity.validUris.get(i).getHost().equals("") ?
+                    GameActivity.validUris.get(i).getScheme() + "://" :
+                    GameActivity.validUris.get(i).getScheme() + "://" + GameActivity.validUris.get(i).getHost() + "/";
+            if (input.startsWith(prefix)) {
+                inputSudoku = input.replace(prefix, "");
+                break;
+            }
+
+            String endOfRecord = (i == GameActivity.validUris.size() - 1) ? "" : ", ";
+            errorMessage.append(prefix);
+            errorMessage.append(endOfRecord);
+        }
+
+        // the inputSudoku variable being null means the input did not match any of the valid prefixes
+        if (inputSudoku == null) {
+            Toast.makeText(CreateSudokuActivity.this,
+                    this.getString(R.string.menu_import_wrong_format_custom_sudoku) + " " + errorMessage.toString(), Toast.LENGTH_LONG).show();
+            return;
+        }
+
+        boolean validSize = Math.sqrt(inputSudoku.length()) == gameController.getSize();
+
+        if (!validSize) {
+            Toast.makeText(CreateSudokuActivity.this, R.string.failed_to_verify_custom_sudoku_toast, Toast.LENGTH_LONG).show();
+            return;
+        }
+
+        //check whether or not the sudoku is valid and has a unique solution
+        boolean solvable = verify(gameController.getGameType(), inputSudoku);
+
+        // if the encoded sudoku is solvable, sent the code directly to the GameActivity; if not, notify the user
+        if (solvable) {
+           int boardSize = gameController.getGameType().getSize() * gameController.getGameType().getSize();
+            GameInfoContainer container = new GameInfoContainer(0, GameDifficulty.Unspecified,
+                    gameController.getGameType(), new int [boardSize], new int [boardSize],
+                    new boolean [boardSize][gameController.getGameType().getSize()]);
+            container.parseSetValues(inputSudoku);
+
+            gameController.loadLevel(container);
+            setUpLayout();
+
+        } else {
+            Toast.makeText(CreateSudokuActivity.this, R.string.failed_to_verify_custom_sudoku_toast, Toast.LENGTH_LONG).show();
+        }
+    }
+
+    /**
+     * Implements the onDialogNegativeClick() method of the IFinalizeDialogFragmentListener
+     * interface.
+     */
+    public void onDialogNegativeClick() {
+
+    }
+
+    @Override
+    public void onSaveInstanceState(Bundle savedInstanceState) {
+        // Always call the superclass so it can save the view hierarchy state
+        super.onSaveInstanceState(savedInstanceState);
+
+        // Save the user's current game state
+        savedInstanceState.putParcelable("gameController", gameController);
+
+    }
+
+    @Override
+    public void onRestoreInstanceState(Bundle savedInstanceState) {
+        super.onRestoreInstanceState(savedInstanceState);
+
+        gameController = savedInstanceState.getParcelable("gameController");
+    }
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/DailySudokuActivity.java

@@ -0,0 +1,272 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.secuso.privacyfriendlysudoku.ui;
+
+import android.content.Context;
+import android.content.Intent;
+import android.content.SharedPreferences;
+import android.os.Bundle;
+import android.preference.PreferenceManager;
+import android.view.LayoutInflater;
+import android.view.Menu;
+import android.view.MenuItem;
+import android.view.ViewGroup;
+import android.widget.BaseAdapter;
+import android.widget.ImageView;
+import android.widget.ListView;
+import android.widget.TextView;
+import android.view.View;
+import android.widget.RatingBar;
+import android.widget.Toast;
+import org.secuso.privacyfriendlysudoku.controller.GameController;
+import org.secuso.privacyfriendlysudoku.controller.GameStateManager;
+import org.secuso.privacyfriendlysudoku.controller.NewLevelManager;
+import org.secuso.privacyfriendlysudoku.controller.database.DatabaseHelper;
+import org.secuso.privacyfriendlysudoku.controller.database.model.DailySudoku;
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.appcompat.widget.Toolbar;
+
+import org.secuso.privacyfriendlysudoku.controller.qqwing.QQWing;
+import org.secuso.privacyfriendlysudoku.game.GameDifficulty;
+import org.secuso.privacyfriendlysudoku.game.GameType;
+import org.secuso.privacyfriendlysudoku.ui.view.R;
+
+import java.text.DateFormat;
+import java.util.Calendar;
+import java.util.List;
+import java.util.Locale;
+import java.util.TimeZone;
+
+/**
+ *The DailySudokuActivity is an activity that extends the AppCompatActivity.
+ *The activity is responsible for the logic of the DailySudoku.
+ *DailySudoku is a game mode where every day a different Sudoku is created for the user
+ */
+public class DailySudokuActivity extends AppCompatActivity {
+
+    List<DailySudoku> sudokuList;
+    SharedPreferences settings;
+    private final DatabaseHelper dbHelper = new DatabaseHelper(this);
+    RatingBar difficultyBar;
+    private SudokuListAdapter sudokuListAdapter;
+    private int dailyId;
+
+
+    @Override
+    public void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        setContentView(R.layout.activity_daily_sudoku);
+        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
+        setSupportActionBar(toolbar);
+
+        sudokuList = dbHelper.getDailySudokus();
+        TextView totalGamesTextView = findViewById(R.id.numb_of_total_games);
+        TextView hintsTextView = findViewById(R.id.numb_of_hints);
+        TextView totalTimeTextView = findViewById(R.id.numb_of_total_time);
+        totalGamesTextView.setText(String.valueOf(sudokuList.size()));
+
+
+        int sumHints = 0;
+        int sumTime = 0;
+
+        for (DailySudoku sudoku : sudokuList){
+            sumHints += sudoku.getHintsUsed();
+            sumTime += sudoku.getTimeNeededInSeconds();
+        }
+
+        int hours = sumTime / 3600;
+        int minutes = ( sumTime / 60 ) % 60;
+        int seconds = sumTime % 60;
+        String str = String.format(Locale.getDefault(), "%02d:%02d:%02d", hours, minutes, seconds);
+
+        hintsTextView.setText(String.valueOf(sumHints));
+        totalTimeTextView.setText(str);
+
+        androidx.appcompat.app.ActionBar actionBar = getSupportActionBar();
+        actionBar.setTitle(R.string.menu_daily_sudoku);
+        actionBar.setDisplayHomeAsUpEnabled(true);
+
+        difficultyBar = findViewById(R.id.first_diff_bar);
+        settings = PreferenceManager.getDefaultSharedPreferences(this);
+
+        ListView listView = (ListView)findViewById(R.id.sudoku_list);
+        sudokuListAdapter = new SudokuListAdapter(this, sudokuList);
+        listView.setAdapter(sudokuListAdapter);
+
+        // Calculate the current date as an int id
+        Calendar currentDate = Calendar.getInstance();
+        dailyId = currentDate.get(Calendar.DAY_OF_MONTH) * 1000000
+                + (currentDate.get(Calendar.MONTH) + 1) * 10000 + currentDate.get(Calendar.YEAR);
+
+        GameDifficulty dailyDifficulty;
+
+        //only calculate the difficulty of the daily sudoku once a day
+        if (settings.getInt("lastCalculated", 0) != dailyId) {
+            // generate the daily sudoku
+            NewLevelManager newLevelManager = NewLevelManager.getInstance(getApplicationContext(), settings);
+            int[] level = newLevelManager.loadDailySudoku();
+            QQWing difficultyCheck = new QQWing(GameType.Default_9x9, GameDifficulty.Unspecified);
+
+            difficultyCheck.setRecordHistory(true);
+            difficultyCheck.setPuzzle(level);
+            difficultyCheck.solve();
+
+            dailyDifficulty = difficultyCheck.getDifficulty();
+
+            //save the index of the daily difficulty (in the valid difficulty list) and the day it was calculated for
+            SharedPreferences.Editor editor = settings.edit();
+            editor.putInt("lastCalculated", dailyId);
+            editor.putInt("dailyDifficultyIndex", GameDifficulty.getValidDifficultyList().indexOf(dailyDifficulty));
+            editor.apply();
+
+        } else {
+            // if the daily sudoku has been calculated already, the difficulty can be read from the settings attribute
+            int index = settings.getInt("dailyDifficultyIndex", GameDifficulty.getValidDifficultyList()
+                    .indexOf(GameDifficulty.Unspecified));
+            dailyDifficulty = GameDifficulty.getValidDifficultyList().get(index);
+        }
+
+        TextView diffTextView = findViewById(R.id.first_diff_text);
+
+        diffTextView.setText(dailyDifficulty.getStringResID());
+        difficultyBar.setNumStars(GameDifficulty.getValidDifficultyList().size());
+        difficultyBar.setMax(GameDifficulty.getValidDifficultyList().size());
+        difficultyBar.setRating(GameDifficulty.getValidDifficultyList().indexOf(dailyDifficulty)+1);
+    }
+
+    public void onClick(View view) {
+        final Intent intent = new Intent(this,GameActivity.class);
+
+        /*
+         If the 'lastPlayed' key does not return the calculated id, then the player has not played
+         the sudoku of the day yet, meaning it has yet to be saved on their phone and needs to be generated again
+         */
+        if (settings.getInt("lastPlayed", 0) != dailyId) {
+            SharedPreferences.Editor editor = settings.edit();
+            editor.putInt("lastPlayed", dailyId);
+
+            //as the player just started a new daily sudoku, set the 'finishedForToday' setting to 'false'
+            editor.putBoolean("finishedForToday", false);
+            editor.apply();
+
+            //send everything to game activity, which calculates the daily sudoku
+            intent.putExtra("isDailySudoku", true);
+            startActivity(intent);
+
+        } else if (!settings.getBoolean("finishedForToday", true)) {
+            /*
+            if the 'finished for today' setting is 'false', the player has already started the sudoku
+            but has yet to finish it -> send the designated daily sudoku ID to the GameActivity
+             */
+            GameStateManager fm = new GameStateManager(getBaseContext(), settings);
+            fm.loadGameStateInfo();
+            intent.putExtra("loadLevel", true);
+            intent.putExtra("loadLevelID", GameController.DAILY_SUDOKU_ID);
+            startActivity(intent);
+        } else {
+            Toast.makeText(this, R.string.finished_daily_sudoku, Toast.LENGTH_LONG).show();
+        }
+    }
+    
+    public boolean onCreateOptionsMenu(Menu menu) {
+        return true;
+    }
+
+    @Override
+    public boolean onOptionsItemSelected(MenuItem item) {
+        // Handle action bar item clicks here. The action bar will
+        // automatically handle clicks on the Home/Up button, so long
+        // as you specify a parent activity in AndroidManifest.xml.
+
+        //noinspection SimplifiableIfStatement
+        if (item.getItemId() == android.R.id.home) {
+            finish();
+            return true;
+        }
+
+        return super.onOptionsItemSelected(item);
+    }
+
+    private static class SudokuListAdapter extends BaseAdapter {
+
+        private Context context;
+        private List<DailySudoku> sudokuList;
+
+        public SudokuListAdapter(Context context, List<DailySudoku> sudokuList) {
+            this.context = context;
+            this.sudokuList = sudokuList;
+        }
+
+        @Override
+        public int getCount() {
+            return sudokuList.size();
+        }
+
+        @Override
+        public Object getItem(int position) {
+            return sudokuList.get(position);
+        }
+
+        @Override
+        public long getItemId(int position) {
+            return position;
+        }
+
+        @Override
+        public View getView(int position, View convertView, ViewGroup parent) {
+            DailySudoku sudoku = sudokuList.get(position);
+
+            if (convertView == null) {
+                LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
+                convertView = (View) inflater.inflate(R.layout.list_entry_layout, null);
+            }
+
+            TextView gameType = (TextView)convertView.findViewById(R.id.loadgame_listentry_gametype);
+            TextView difficulty =(TextView)convertView.findViewById(R.id.loadgame_listentry_difficultytext);
+            RatingBar difficultyBar =(RatingBar)convertView.findViewById(R.id.loadgame_listentry_difficultybar);
+            TextView playedTime = (TextView)convertView.findViewById(R.id.loadgame_listentry_timeplayed);
+            TextView lastTimePlayed = (TextView)convertView.findViewById(R.id.loadgame_listentry_lasttimeplayed);
+            ImageView image = (ImageView)convertView.findViewById(R.id.loadgame_listentry_gametypeimage);
+            ImageView customImage = (ImageView)convertView.findViewById(R.id.loadgame_listentry_custom_icon);
+
+
+            image.setImageResource(R.drawable.icon_default_9x9);
+
+            gameType.setText(sudoku.getGameType().getStringResID());
+            difficulty.setText(sudoku.getDifficulty().getStringResID());
+            difficultyBar.setNumStars(GameDifficulty.getValidDifficultyList().size());
+            difficultyBar.setMax(GameDifficulty.getValidDifficultyList().size());
+            difficultyBar.setRating(GameDifficulty.getValidDifficultyList().indexOf(sudoku.getDifficulty())+1);
+            customImage.setVisibility(View.INVISIBLE);
+
+
+            int id = sudoku.getId();
+            Calendar cal = Calendar.getInstance();
+            cal.set(id%10000, (id/10000) % 100, id/1000000, 0, 0, 0 );
+
+
+            DateFormat format = DateFormat.getDateInstance();
+            format.setTimeZone(TimeZone.getDefault());
+
+            lastTimePlayed.setText(format.format(cal.getTime()));
+
+            playedTime.setText(sudoku.getTimeNeeded());
+            return convertView;
+        }
+    }
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/GameActivity.java

@@ -1,24 +1,49 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
 import android.app.Activity;
 import android.app.AlertDialog;
 import android.app.Dialog;
 import android.app.DialogFragment;
+import android.content.ClipData;
+import android.content.ClipboardManager;
+import android.content.Context;
 import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.content.res.Configuration;
 import android.graphics.Point;
+import android.net.Uri;
 import android.os.Bundle;
 import android.preference.PreferenceActivity;
 import android.preference.PreferenceManager;
 import com.google.android.material.navigation.NavigationView;
+
+import androidx.appcompat.app.AppCompatDelegate;
 import androidx.core.view.GravityCompat;
 import androidx.drawerlayout.widget.DrawerLayout;
 import androidx.appcompat.app.ActionBarDrawerToggle;
 import androidx.appcompat.app.AppCompatActivity;
 import androidx.appcompat.widget.Toolbar;
+
+import android.util.Log;
 import android.view.Gravity;
+import android.view.LayoutInflater;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
@@ -27,28 +52,40 @@ import android.widget.Button;
 import android.widget.LinearLayout;
 import android.widget.RatingBar;
 import android.widget.TextView;
+import android.widget.Toast;
 
 import org.secuso.privacyfriendlysudoku.controller.GameController;
 import org.secuso.privacyfriendlysudoku.controller.GameStateManager;
 import org.secuso.privacyfriendlysudoku.controller.SaveLoadStatistics;
 import org.secuso.privacyfriendlysudoku.controller.Symbol;
 import org.secuso.privacyfriendlysudoku.controller.helper.GameInfoContainer;
+import org.secuso.privacyfriendlysudoku.controller.qqwing.QQWing;
 import org.secuso.privacyfriendlysudoku.game.GameDifficulty;
 import org.secuso.privacyfriendlysudoku.game.GameType;
 import org.secuso.privacyfriendlysudoku.game.listener.IGameSolvedListener;
 import org.secuso.privacyfriendlysudoku.game.listener.ITimerListener;
 import org.secuso.privacyfriendlysudoku.ui.listener.IHintDialogFragmentListener;
 import org.secuso.privacyfriendlysudoku.ui.listener.IResetDialogFragmentListener;
+import org.secuso.privacyfriendlysudoku.ui.listener.IShareDialogFragmentListener;
 import org.secuso.privacyfriendlysudoku.ui.view.R;
 import org.secuso.privacyfriendlysudoku.ui.view.SudokuFieldLayout;
 import org.secuso.privacyfriendlysudoku.ui.view.SudokuKeyboardLayout;
 import org.secuso.privacyfriendlysudoku.ui.view.SudokuSpecialButtonLayout;
 import org.secuso.privacyfriendlysudoku.ui.view.WinDialog;
+import org.secuso.privacyfriendlysudoku.ui.view.databinding.DialogFragmentShareBoardBinding;
 
+
+import java.util.Arrays;
 import java.util.LinkedList;
 import java.util.List;
 
-public class GameActivity extends BaseActivity implements NavigationView.OnNavigationItemSelectedListener, IGameSolvedListener ,ITimerListener, IHintDialogFragmentListener, IResetDialogFragmentListener {
+public class GameActivity extends BaseActivity implements NavigationView.OnNavigationItemSelectedListener, IGameSolvedListener ,ITimerListener, IHintDialogFragmentListener, IResetDialogFragmentListener, IShareDialogFragmentListener {
+
+     public static final List<Uri> validUris = Arrays.asList(
+             Uri.parse("https://sudoku.secuso.org"),
+             Uri.parse("http://sudoku.secuso.org"),
+             Uri.parse("sudoku://")
+     );
 
     GameController gameController;
     SudokuFieldLayout layout;
@@ -57,15 +94,27 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
     TextView timerView;
     TextView viewName ;
     RatingBar ratingBar;
-    private boolean gameSolved = false;
     SaveLoadStatistics statistics = new SaveLoadStatistics(this);
     WinDialog dialog = null;
+    private boolean gameSolved = false;
+    private boolean startGame = true;
+
+    public static String timeToString(int time) {
+        int seconds = time % 60;
+        int minutes = ((time - seconds) / 60) % 60;
+        int hours = (time - minutes - seconds) / (3600);
+        String h, m, s;
+        s = (seconds < 10) ? "0" + String.valueOf(seconds) : String.valueOf(seconds);
+        m = (minutes < 10) ? "0" + String.valueOf(minutes) : String.valueOf(minutes);
+        h = (hours < 10) ? "0" + String.valueOf(hours) : String.valueOf(hours);
+        return h + ":" + m + ":" + s;
+    }
 
     @Override
     protected void onPostCreate(Bundle savedInstanceState) {
         super.onPostCreate(savedInstanceState);
 
-        if(gameSolved) {
+        if(gameSolved || !startGame) {
             gameController.pauseTimer();
         } else {
             // start the game
@@ -80,41 +129,165 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-
         SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(this);
 
+        /*
+        If the app is started via a deeplink, the GameActivity is the first activity the user accesses,
+        so we need to set the dark mode settings in this activity as well
+         */
+        if (sharedPref.getBoolean("pref_dark_mode_setting", false )) {
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
+        } else if (sharedPref.getBoolean("pref_dark_mode_automatically_by_system", false)) {
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM);
+
+        } else if(sharedPref.getBoolean("pref_dark_mode_automatically_by_battery", false)){
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_AUTO_BATTERY);
+        } else {
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
+        }
+
         if(sharedPref.getBoolean("pref_keep_screen_on", true)) {
             getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
         }
 
+        super.onCreate(savedInstanceState);
+
         GameType gameType = GameType.Unspecified;
         GameDifficulty gameDifficulty = GameDifficulty.Unspecified;
         int loadLevelID = 0;
         boolean loadLevel = false;
 
-        if(savedInstanceState == null) {
+         if(savedInstanceState == null) {
 
             Bundle extras = getIntent().getExtras();
-            if (extras != null) {
-                gameType = GameType.valueOf(extras.getString("gameType", GameType.Default_9x9.name()));
-                gameDifficulty = GameDifficulty.valueOf(extras.getString("gameDifficulty", GameDifficulty.Moderate.name()));
-                loadLevel = extras.getBoolean("loadLevel", false);
-                if (loadLevel) {
-                    loadLevelID = extras.getInt("loadLevelID");
-                }
-            }
 
+            /*
+            If a (deep) link is used to access the activity, the content of the link cannot be accessed
+            as a part of the getExtras() bundle. Instead, it needs to be saved as an URI object
+             */
+            Uri data = getIntent().getData();
             gameController = new GameController(sharedPref, getApplicationContext());
 
-            List<GameInfoContainer> loadableGames = GameStateManager.getLoadableGameList();
+            // Intents coming from the LoadGameActivity and MainActivity can be identified based on the keys the getExtras() bundle contains
+            boolean intentReceivedFromMainActivity = extras != null &&
+                    (extras.containsKey("gameType") || extras.containsKey("loadLevel"));
+
+            /*
+            If data is not null and the intent was not received from the MainActivity/ LoadGameActivity, the source of the intent must be the
+            CreateSudokuActivity, the ImportBoardDialog or a deep link, meaning data carries an URI containing an encoded sudoku
+             */
+            if (data != null && !intentReceivedFromMainActivity) {
+                // extract encoded sudoku board from the URI
+                String input = "";
+
+                for (int i = 0; i < validUris.size(); i++) {
+                    if (data.getScheme().equals(validUris.get(i).getScheme())) {
+                        if (validUris.get(i).getHost().equals("")) {
+                            input = data.getHost();
+                            break;
+                        }
+                        else if (data.getHost().equals(validUris.get(i).getHost())) {
+                            input = data.getPath();
+                            input =input.replace("/", "");
+                            break;
+                        }
+                    }
+                }
+
+                // Save all of the information that can be extracted from the encoded board in a GameInfoContainer object
+                int sectionSize = (int)Math.sqrt(input.length());
+                int boardSize = sectionSize * sectionSize;
+                QQWing difficultyCheck;
+                GameInfoContainer container = new GameInfoContainer(0, GameDifficulty.Unspecified,
+                        GameType.Unspecified, new int [boardSize], new int [boardSize], new boolean [boardSize][sectionSize]);
+                container.setCustom(extras != null && extras.getBoolean("isCustom", false));
+
+                try {
+                    container.parseGameType("Default_" + sectionSize + "x" + sectionSize);
+                    container.parseFixedValues(input);
+                    difficultyCheck = new QQWing(container.getGameType(), GameDifficulty.Unspecified);
+
+                    // calculate difficulty of the imported sudoku
+                    difficultyCheck.setRecordHistory(true);
+                    difficultyCheck.setPuzzle(container.getFixedValues());
+                    difficultyCheck.solve();
+
+                    container.parseDifficulty(difficultyCheck.getDifficulty().toString());
+
+                    // A sudoku is that does not have a unique solution is deemed 'unplayable' and may not be started
+                    startGame = difficultyCheck.hasUniqueSolution();
+
+
+                } catch (IllegalArgumentException e) {
+                    // If the imported code does not actually encode a valid sudoku, it needs to be rejected
+                    startGame = false;
+
+                    /*
+                     set up a blank sudoku field that can be displayed in the activity while the player is notified that
+                     the link they imported does not encode a valid sudoku
+                     */
+                    sectionSize = GameType.Default_9x9.getSize();
+                    boardSize = sectionSize * sectionSize;
+                    container = new GameInfoContainer(0, GameDifficulty.Unspecified,
+                            GameType.Default_9x9, new int [boardSize], new int [boardSize], new boolean [boardSize][sectionSize]);
+                }
+
+                // Notify the user if the sudoku they tried to import cannot be played and finish the activity
+                if (!startGame) {
+                    AlertDialog.Builder builder = new AlertDialog.Builder(GameActivity.this, R.style.AppTheme_Dialog);
+                    builder.setMessage(R.string.impossible_import_notice)
+                            .setCancelable(false)
+                            .setPositiveButton(R.string.okay, new DialogInterface.OnClickListener() {
+                                public void onClick(DialogInterface dialog, int id) {
+                                    finish();
+                                }
+                            });
+                    AlertDialog alert = builder.create();
+                    alert.show();
+                }
+
+                gameController.loadLevel(container);
 
-            if (loadLevel && loadableGames.size() > loadLevelID) {
-                // load level from GameStateManager
-                gameController.loadLevel(loadableGames.get(loadLevelID));
             } else {
-                // load a new level
+                boolean isDailySudoku = false;
-                gameController.loadNewLevel(gameType, gameDifficulty);
+                if (extras != null) {
+                    gameType = GameType.valueOf(extras.getString("gameType", GameType.Default_9x9.name()));
+                    gameDifficulty = GameDifficulty.valueOf(extras.getString("gameDifficulty", GameDifficulty.Moderate.name()));
+                    isDailySudoku = extras.getBoolean("isDailySudoku", false);
+                    loadLevel = extras.getBoolean("loadLevel", false);
+                    if (loadLevel) {
+                        loadLevelID = extras.getInt("loadLevelID");
+                    }
+                }
+
+                /*
+                The 'isDailySudoku' key is only set by the DailySudokuActivity if a new daily sudoku needs to be calculated;
+                otherwise, the extras simply contain the id of the daily sudoku. Therefore, calculate the new daily sudoko if
+                'isDailySudoku' is true
+                 */
+                if (isDailySudoku) {
+                    gameController.loadNewDailySudokuLevel();
+                } else  {
+
+                    List<GameInfoContainer> loadableGames = GameStateManager.getLoadableGameList();
+
+                    if (loadLevel) {
+                        if (loadableGames.size() > loadLevelID) {
+                            // load level from GameStateManager
+                            gameController.loadLevel(loadableGames.get(loadLevelID));
+                        } else if (loadLevelID == GameController.DAILY_SUDOKU_ID) {
+                            for (GameInfoContainer container : loadableGames) {
+                                if (container.getID() == loadLevelID) {
+                                    gameController.loadLevel(container);
+                                    break;
+                                }
+                            }
+                        }
+                    } else {
+                        // load a new level
+                        gameController.loadNewLevel(gameType, gameDifficulty);
+                    }
+                }
             }
         } else {
             gameController = savedInstanceState.getParcelable("gameController");
@@ -170,7 +343,7 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
 
         //set Special keys
         specialButtonLayout = (SudokuSpecialButtonLayout) findViewById(R.id.sudokuSpecialLayout);
-        specialButtonLayout.setButtons(p.x, gameController, keyboard, getFragmentManager(), orientation);
+        specialButtonLayout.setButtons(p.x, gameController, keyboard, getFragmentManager(), orientation, GameActivity.this);
 
         //set TimerView
         timerView = (TextView)findViewById(R.id.timerView);
@@ -217,11 +390,21 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
     @Override
     public void onPause(){
         super.onPause();
-        if(!gameSolved) {
+
+        // Do not save solved or unplayable sudokus
+        if(!gameSolved && startGame) {
             gameController.saveGame(this);
         }
         gameController.deleteTimer();
     }
+
+    @Override
+    public void onNewIntent(Intent intent) {
+        super.onNewIntent(intent);
+        startActivity(intent);
+        finish();
+    }
+
     @Override
     public void onResume(){
         super.onResume();
@@ -233,7 +416,7 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
 
         gameController.initTimer();
 
-        if(!gameSolved) {
+        if(!gameSolved && startGame) {
             mHandler.postDelayed(new Runnable() {
                 @Override
                 public void run() {
@@ -253,6 +436,12 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
         keyboard.setSymbols(s);
     }
 
+    /*@Override
+    public boolean onCreateOptionsMenu(Menu menu) {
+        // Inflate the menu; this adds items to the action bar if it is present.
+        getMenuInflater().inflate(R.menu.game_view, menu);
+        return true;
+    }*/
 
     @Override
     public void onBackPressed() {
@@ -265,13 +454,6 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
         }
     }
 
-    /*@Override
-    public boolean onCreateOptionsMenu(Menu menu) {
-        // Inflate the menu; this adds items to the action bar if it is present.
-        getMenuInflater().inflate(R.menu.game_view, menu);
-        return true;
-    }*/
-
     @SuppressWarnings("StatementWithEmptyBody")
     @Override
     public boolean onNavigationItemSelected(MenuItem item) {
@@ -286,6 +468,39 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
                 resetDialog.show(getFragmentManager(), "ResetDialogFragment");
                 break;
 
+            case R.id.menu_share:
+                // Create import link from current sudoku board
+                String scheme = GameActivity.validUris.size() > 0 ? GameActivity.validUris.get(0).getScheme()
+                        + "://" + GameActivity.validUris.get(0).getHost() : "";
+                if (!scheme.equals("") && !scheme.endsWith("/")) scheme = scheme + "/";
+                String codeForClipboard = scheme + gameController.getCodeOfField();
+
+                // Create new ShareBoardDialog using the previously created links
+                ShareBoardDialog shareDialog = new ShareBoardDialog();
+                shareDialog.setDisplayCode(codeForClipboard);
+                shareDialog.setCopyClickListener(new View.OnClickListener() {
+                    @Override
+                    public void onClick(View v) {
+                        // remember to include alternate code for older android versions
+
+                        //save link to clipboard
+                        ClipboardManager clipboard = (ClipboardManager) getSystemService(Context.CLIPBOARD_SERVICE);
+
+                        if (clipboard != null) {
+                            ClipData clip = ClipData.newPlainText("BoardCode", codeForClipboard);
+                            clipboard.setPrimaryClip(clip);
+                            Toast.makeText(GameActivity.this, R.string.copy_code_confirmation_toast,
+                                    Toast.LENGTH_LONG).show();
+                        } else {
+                            Toast.makeText(GameActivity.this, R.string.copy_code_error_toast,
+                                    Toast.LENGTH_LONG).show();
+                        }
+                    }
+                });
+                shareDialog.show(getFragmentManager(), "ShareDialogFragment");
+
+                break;
+
             case R.id.nav_newgame:
                 //create new game
                 intent = new Intent(this, MainActivity.class);
@@ -296,8 +511,6 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
             case R.id.menu_settings:
                 //open settings
                 intent = new Intent(this,SettingsActivity.class);
-                intent.putExtra( PreferenceActivity.EXTRA_SHOW_FRAGMENT, SettingsActivity.GamePreferenceFragment.class.getName() );
-                intent.putExtra( PreferenceActivity.EXTRA_NO_HEADERS, true );
                 break;
 
             case R.id.nav_highscore:
@@ -341,7 +554,6 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
         return true;
     }
 
-
     @Override
     public void onSolved() {
         gameSolved = true;
@@ -350,12 +562,33 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
         gameController.deleteGame(this);
         disableReset();
 
-        //Show time hints new plus old best time
+        //Save solved sudoku, if it happens to be a daily sudoku, to daily sudoku database
+        if(gameController.getGameID() == GameController.DAILY_SUDOKU_ID) {
+            gameController.saveDailySudoku(GameActivity.this);
+            SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(this);
+            SharedPreferences.Editor editor = sharedPref.edit();
+            /*
+             set 'finishedForToday' setting to 'true', signifying that the player has solved the daily
+             sudoku and can no longer play it today
+             */
+            editor.putBoolean("finishedForToday", true);
+            editor.apply();
+        }
 
-        statistics.saveGameStats();
+        //Don't save statistics if game is custom
+        boolean isNewBestTime;
+
+        if (!gameController.gameIsCustom()) {
+            //Show time hints new plus old best time
+            statistics.saveGameStats();
+            isNewBestTime = gameController.getUsedHints() == 0
+                    && statistics.loadStats(gameController.getGameType(),gameController.getDifficulty()).getMinTime() >= gameController.getTime();
+
+        } else {
+            // cannot be best time if sudoku is custom
+            isNewBestTime = false;
+        }
 
-        boolean isNewBestTime = gameController.getUsedHints() == 0
-                && statistics.loadStats(gameController.getGameType(),gameController.getDifficulty()).getMinTime() >= gameController.getTime();
 
         dialog = new WinDialog(this, R.style.WinDialog , timeToString(gameController.getTime()), String.valueOf(gameController.getUsedHints()), isNewBestTime);
 
@@ -395,18 +628,6 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
         specialButtonLayout.setButtonsEnabled(false);
     }
 
-    public String timeToString(int time) {
-        int seconds = time % 60;
-        int minutes = ((time - seconds) / 60) % 60;
-        int hours = (time - minutes - seconds) / (3600);
-        String h, m, s;
-        s = (seconds < 10) ? "0" + String.valueOf(seconds) : String.valueOf(seconds);
-        m = (minutes < 10) ? "0" + String.valueOf(minutes) : String.valueOf(minutes);
-        h = (hours < 10) ? "0" + String.valueOf(hours) : String.valueOf(hours);
-        return h + ":" + m + ":" + s;
-    }
-
-
     private void disableReset(){
         NavigationView navView = (NavigationView)findViewById(R.id.nav_view);
         Menu navMenu = navView.getMenu();
@@ -418,7 +639,7 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
         // display the time
         timerView.setText(timeToString(time));
 
-        if(gameSolved) return;
+        if(gameSolved || !startGame) return;
         // save time
         gameController.saveGame(this);
     }
@@ -433,11 +654,100 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
         gameController.resetLevel();
     }
 
+    @Override
+    public void onShareDialogPositiveClick(String input) {
+        Intent sendBoardIntent = new Intent();
+        sendBoardIntent.setAction(Intent.ACTION_SEND);
+        sendBoardIntent.putExtra(Intent.EXTRA_TEXT, input);
+        sendBoardIntent.setType("text/plain");
+
+        Intent shareBoardIntent = Intent.createChooser(sendBoardIntent, null);
+        startActivity(shareBoardIntent);
+    }
+
     @Override
     public void onDialogNegativeClick() {
         // do nothing
     }
 
+    @Override
+    public void onSaveInstanceState(Bundle savedInstanceState) {
+        // Always call the superclass so it can save the view hierarchy state
+        super.onSaveInstanceState(savedInstanceState);
+
+        // Save the user's current game state
+        savedInstanceState.putParcelable("gameController", gameController);
+        savedInstanceState.putBoolean("gameSolved", gameSolved);
+    }
+
+    @Override
+    public void onRestoreInstanceState(Bundle savedInstanceState) {
+        super.onRestoreInstanceState(savedInstanceState);
+
+        gameController = savedInstanceState.getParcelable("gameController");
+        gameSolved = savedInstanceState.getBoolean("gameSolved");
+    }
+
+    public static class ShareBoardDialog extends DialogFragment {
+        private LinkedList<IShareDialogFragmentListener> listeners = new LinkedList<>();
+
+        /*declare empty display code and click listener in case anyone
+         * tries to call the ShareBoardDialog without setting those attributes first
+         */
+
+        private String displayCode = "";
+        private View.OnClickListener copyClickListener = new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+
+            }
+        };
+
+        public void setDisplayCode(String displayCode) {
+            this.displayCode = displayCode;
+        }
+
+        public void setCopyClickListener(View.OnClickListener listener) {
+            copyClickListener = listener;
+        }
+
+        @Override
+        public void onAttach(Activity activity) {
+            super.onAttach(activity);
+            // Verify that the host activity implements the callback interface
+            if(activity instanceof IShareDialogFragmentListener) {
+                listeners.add((IShareDialogFragmentListener) activity);
+            }
+        }
+
+        @Override
+        public Dialog onCreateDialog(Bundle savedInstanceState) {
+            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(), R.style.AppTheme_Dialog);
+
+            LayoutInflater inflater = getActivity().getLayoutInflater();
+            DialogFragmentShareBoardBinding binding = DialogFragmentShareBoardBinding.inflate(inflater);
+
+            binding.ver3DisplaySudokuTextView.setText(displayCode);
+            binding.ver3DisplaySudokuTextView.setEnabled(false);
+            binding.ver3CopySudokuToClipboardButton.setOnClickListener(copyClickListener);
+            builder.setView(binding.getRoot());
+
+            builder.setPositiveButton(R.string.share_confirmation_confirm, new DialogInterface.OnClickListener() {
+                        public void onClick(DialogInterface dialog, int id) {
+                            for(IShareDialogFragmentListener l : listeners) {
+                                l.onShareDialogPositiveClick(binding.ver3DisplaySudokuTextView.getText().toString());
+                            }
+                        }
+                    })
+                    .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
+                        public void onClick(DialogInterface dialog, int id) {
+                            // User cancelled the dialog
+                        }
+                    });
+            return builder.create();
+        }
+    }
+
     public static class ResetConfirmationDialog extends DialogFragment {
 
         LinkedList<IResetDialogFragmentListener> listeners = new LinkedList<>();
@@ -454,7 +764,7 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
         @Override
         public Dialog onCreateDialog(Bundle savedInstanceState) {
             // Use the Builder class for convenient dialog construction
-            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
+            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(), R.style.AppTheme_Dialog);
             builder.setMessage(R.string.reset_confirmation)
                     .setPositiveButton(R.string.reset_confirmation_confirm, new DialogInterface.OnClickListener() {
                         public void onClick(DialogInterface dialog, int id) {
@@ -472,20 +782,4 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
         }
     }
 
-    @Override
-    public void onSaveInstanceState(Bundle savedInstanceState) {
-        // Save the user's current game state
-
-        savedInstanceState.putParcelable("gameController", gameController);
-        savedInstanceState.putInt("gameSolved", gameSolved ? 1 : 0);
-
-        // Always call the superclass so it can save the view hierarchy state
-        super.onSaveInstanceState(savedInstanceState);
-    }
-
-    @Override
-    public void onRestoreInstanceState(Bundle savedInstanceState) {
-        //super.onRestoreInstanceState(savedInstanceState);
-    }
-
 }

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/HelpActivity.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
 

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/LoadGameActivity.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
 import android.app.Activity;
@@ -21,6 +37,7 @@ import android.widget.ListView;
 import android.widget.RatingBar;
 import android.widget.TextView;
 
+import org.secuso.privacyfriendlysudoku.controller.GameController;
 import org.secuso.privacyfriendlysudoku.controller.GameStateManager;
 import org.secuso.privacyfriendlysudoku.controller.helper.GameInfoContainer;
 import org.secuso.privacyfriendlysudoku.game.GameDifficulty;
@@ -70,6 +87,13 @@ public class LoadGameActivity extends BaseActivity implements IDeleteDialogFragm
         GameStateManager gameStateManager = new GameStateManager(this, settings);
         loadableGameList = gameStateManager.loadGameStateInfo();
 
+        for (GameInfoContainer container : loadableGameList) {
+            if (container.getID() == GameController.DAILY_SUDOKU_ID) {
+                loadableGameList.remove(container);
+                break;
+            }
+        }
+
         AdapterView.OnItemClickListener clickListener = new AdapterView.OnItemClickListener() {
             @Override
             public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
@@ -137,7 +161,7 @@ public class LoadGameActivity extends BaseActivity implements IDeleteDialogFragm
         @Override
         public Dialog onCreateDialog(Bundle savedInstanceState) {
             // Use the Builder class for convenient dialog construction
-            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
+            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(), R.style.AppTheme_Dialog);
             builder.setMessage(R.string.loadgame_delete_confirmation)
                     .setPositiveButton(R.string.loadgame_delete_confirm, new DialogInterface.OnClickListener() {
                         public void onClick(DialogInterface dialog, int id) {
@@ -201,6 +225,8 @@ public class LoadGameActivity extends BaseActivity implements IDeleteDialogFragm
             TextView playedTime = (TextView)convertView.findViewById(R.id.loadgame_listentry_timeplayed);
             TextView lastTimePlayed = (TextView)convertView.findViewById(R.id.loadgame_listentry_lasttimeplayed);
             ImageView image = (ImageView)convertView.findViewById(R.id.loadgame_listentry_gametypeimage);
+            ImageView customImage = (ImageView)convertView.findViewById(R.id.loadgame_listentry_custom_icon);
+            TextView customLabel = (TextView) convertView.findViewById(R.id.loadgame_listentry_custom_label);
 
             switch(gic.getGameType()) {
                 case Default_6x6:
@@ -221,6 +247,9 @@ public class LoadGameActivity extends BaseActivity implements IDeleteDialogFragm
             difficultyBar.setMax(GameDifficulty.getValidDifficultyList().size());
             difficultyBar.setRating(GameDifficulty.getValidDifficultyList().indexOf(gic.getDifficulty())+1);
 
+            customImage.setImageResource(gic.isCustom() ? R.drawable.ic_circle_blue_36dp : R.drawable.ic_circle_grey_36dp);
+            customLabel.setVisibility(gic.isCustom() ? View.VISIBLE : View.GONE);
+
             int time = gic.getTimePlayed();
             int seconds = time % 60;
             int minutes = ((time -seconds)/60)%60 ;

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/MainActivity.java

@@ -1,11 +1,34 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
+import android.app.Activity;
+import android.app.AlertDialog;
+import android.app.Dialog;
+import android.app.DialogFragment;
+import android.content.DialogInterface;
 import android.content.Intent;
 import android.content.SharedPreferences;
+import android.net.Uri;
 import android.os.Bundle;
-import android.preference.PreferenceActivity;
 import android.preference.PreferenceManager;
 import com.google.android.material.navigation.NavigationView;
+
+import androidx.appcompat.app.AppCompatDelegate;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentManager;
 import androidx.fragment.app.FragmentPagerAdapter;
@@ -13,31 +36,36 @@ import androidx.core.view.GravityCompat;
 import androidx.viewpager.widget.ViewPager;
 import androidx.drawerlayout.widget.DrawerLayout;
 import androidx.appcompat.app.ActionBarDrawerToggle;
-import androidx.appcompat.app.AppCompatActivity;
 import androidx.appcompat.widget.Toolbar;
+
 import android.view.LayoutInflater;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.Button;
+import android.widget.CheckBox;
+import android.widget.CompoundButton;
 import android.widget.ImageView;
 import android.widget.RatingBar;
 import android.widget.TextView;
 import android.widget.Toast;
 
+import org.secuso.privacyfriendlysudoku.controller.GameController;
 import org.secuso.privacyfriendlysudoku.controller.GameStateManager;
 import org.secuso.privacyfriendlysudoku.controller.NewLevelManager;
 import org.secuso.privacyfriendlysudoku.controller.helper.GameInfoContainer;
 import org.secuso.privacyfriendlysudoku.game.GameDifficulty;
 import org.secuso.privacyfriendlysudoku.game.GameType;
+import org.secuso.privacyfriendlysudoku.ui.listener.IImportDialogFragmentListener;
 import org.secuso.privacyfriendlysudoku.ui.view.R;
+import org.secuso.privacyfriendlysudoku.ui.view.databinding.DialogFragmentImportBoardBinding;
 
 import java.util.LinkedList;
 import java.util.List;
 
 import static org.secuso.privacyfriendlysudoku.ui.TutorialActivity.ACTION_SHOW_ANYWAYS;
 
-public class MainActivity extends BaseActivity implements NavigationView.OnNavigationItemSelectedListener{
+public class MainActivity extends BaseActivity implements NavigationView.OnNavigationItemSelectedListener, IImportDialogFragmentListener{
 
     RatingBar difficultyBar;
     TextView difficultyText;
@@ -53,9 +81,20 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-
         settings = PreferenceManager.getDefaultSharedPreferences(this);
+        if (settings.getBoolean("pref_dark_mode_setting", false )) {
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
+
+        } else if (settings.getBoolean("pref_dark_mode_automatically_by_system", false)) {
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM);
+
+        } else if(settings.getBoolean("pref_dark_mode_automatically_by_battery", false)){
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_AUTO_BATTERY);
+        } else {
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
+        }
+
+        super.onCreate(savedInstanceState);
 
         NewLevelManager newLevelManager = NewLevelManager.getInstance(getApplicationContext(), settings);
 
@@ -121,17 +160,44 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
         final LinkedList<GameDifficulty> difficultyList = GameDifficulty.getValidDifficultyList();
         difficultyBar.setNumStars(difficultyList.size());
         difficultyBar.setMax(difficultyList.size());
+        CheckBox createGameBar = (CheckBox) findViewById(R.id.circleButton);
         difficultyBar.setOnRatingBarChangeListener(new RatingBar.OnRatingBarChangeListener() {
             @Override
             public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) {
-                if (rating < 1) {
+                createGameBar.setChecked(false);
-                    ratingBar.setRating(1);
+                ((Button) findViewById(R.id.playButton)).setText(R.string.new_game);
+
+                if (rating >= 1) {
+                    difficultyText.setText(getString(difficultyList.get((int) ratingBar.getRating() - 1).getStringResID()));
+                } else {
+                    difficultyText.setText(R.string.difficulty_custom);
+                    createGameBar.setChecked(true);
+                    ((Button)findViewById(R.id.playButton)).setText(R.string.create_game);
                 }
-                difficultyText.setText(getString(difficultyList.get((int) ratingBar.getRating() - 1).getStringResID()));
             }
         });
-        GameDifficulty lastChosenDifficulty = GameDifficulty.valueOf(settings.getString("lastChosenDifficulty", "Moderate"));
+
-        difficultyBar.setRating(GameDifficulty.getValidDifficultyList().indexOf(lastChosenDifficulty) + 1);
+        createGameBar.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+            @Override
+            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
+                if (isChecked) {
+
+                    difficultyBar.setRating(0);
+                    ((Button)findViewById(R.id.playButton)).setText(R.string.create_game);
+                }
+                createGameBar.setChecked(isChecked);
+            }});
+
+        String retrievedDifficulty = settings.getString("lastChosenDifficulty", "Moderate");
+        GameDifficulty lastChosenDifficulty = GameDifficulty.valueOf(
+                retrievedDifficulty.equals("Custom")? GameDifficulty.Unspecified.toString() : retrievedDifficulty);
+
+        if (lastChosenDifficulty == GameDifficulty.Unspecified) {
+            difficultyBar.setRating(0);
+            createGameBar.setChecked(true);
+        } else {
+            difficultyBar.setRating(GameDifficulty.getValidDifficultyList().indexOf(lastChosenDifficulty) + 1);
+        }
         /*LayerDrawable stars = (LayerDrawable)difficultyBar.getProgressDrawable();
         stars.getDrawable(2).setColorFilter(getResources().getColor(R.color.colorPrimary), PorterDuff.Mode.SRC_ATOP);//Color for Stars fully selected
         stars.getDrawable(1).setColorFilter(getResources().getColor(R.color.middleblue), PorterDuff.Mode.SRC_ATOP);//Color for Stars partially selected
@@ -166,8 +232,6 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
         winScreen.show(fm,"win_screen_layout");*/
 
     }
-
-
     public void onClick(View view) {
 
         Intent i = null;
@@ -184,6 +248,18 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
                 break;
             case R.id.playButton:
                 GameType gameType = GameType.getValidGameTypes().get(mViewPager.getCurrentItem());
+                if (((CheckBox)findViewById(R.id.circleButton)).isChecked()) {
+                    // start CreateSudokuActivity
+                    i = new Intent(this, CreateSudokuActivity.class);
+                    i.putExtra("gameType", gameType.name());
+
+                    SharedPreferences.Editor editor = settings.edit();
+                    editor.putString("lastChosenGameType", gameType.name());
+                    editor.putString("lastChosenDifficulty", "Custom");
+                    editor.apply();
+                    //i.putExtra("gameDifficulty", GameDifficulty.Easy);
+                    break;
+                }
                 int index = difficultyBar.getProgress()-1;
                 GameDifficulty gameDifficulty = GameDifficulty.getValidDifficultyList().get(index < 0 ? 0 : index);
 
@@ -242,7 +318,7 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
         Button continueButton = (Button)findViewById(R.id.continueButton);
         GameStateManager fm = new GameStateManager(getBaseContext(), settings);
         List<GameInfoContainer> gic = fm.loadGameStateInfo();
-        if(gic.size() > 0) {
+        if(gic.size() > 0 && !(gic.size() == 1 && gic.get(0).getID() == GameController.DAILY_SUDOKU_ID)) {
             continueButton.setEnabled(true);
             continueButton.setBackgroundResource(R.drawable.standalone_button);
         } else {
@@ -254,7 +330,7 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
     @Override
     public boolean onNavigationItemSelected(MenuItem item) {
         // Handle navigation view item clicks here.
-        final int id = item.getItemId();
+        int id = item.getItemId();
 
         drawer.closeDrawer(GravityCompat.START);
 
@@ -271,9 +347,9 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
             }
         }, NAVDRAWER_LAUNCH_DELAY);
 
-        // fade out the active activity
+        // fade out the active activity (but not if the user chose to open the ImportBoardDialog)
         View mainContent = findViewById(R.id.main_content);
-        if (mainContent != null) {
+        if (mainContent != null && id != R.id.nav_import_sudoku) {
             mainContent.animate().alpha(0).setDuration(MAIN_CONTENT_FADEOUT_DURATION);
         }
 
@@ -292,11 +368,13 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
         Intent intent;
 
         switch(id) {
+            case R.id.nav_import_sudoku:
+                ImportBoardDialog dialog = new ImportBoardDialog();
+                dialog.show(getFragmentManager(), "ImportDialogFragment");
+                break;
             case R.id.menu_settings_main:
                 //open settings
-                intent = new Intent(this,SettingsActivity.class);
+                intent = new Intent(this, SettingsActivity.class);
-                intent.putExtra( PreferenceActivity.EXTRA_SHOW_FRAGMENT, SettingsActivity.GamePreferenceFragment.class.getName() );
-                intent.putExtra( PreferenceActivity.EXTRA_NO_HEADERS, true );
                 startActivity(intent);
                 overridePendingTransition(0, 0);
                 break;
@@ -330,6 +408,12 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
                 overridePendingTransition(0, 0);
                 break;
 
+            case R.id.nav_dailySudoku_main:
+                intent = new Intent(this, DailySudokuActivity.class);
+                startActivity(intent);
+                overridePendingTransition(0, 0);
+                break;
+
             default:
         }
         return true;
@@ -345,6 +429,106 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
         return super.onOptionsItemSelected(item);
     }*/
 
+    public void onImportDialogPositiveClick(String input) {
+        String inputSudoku = null;
+        String prefix = "";
+        StringBuilder errorMessage = new StringBuilder();
+
+        // a valid input needs to contain exactly one of the valid prefixes
+        for (int i = 0; i < GameActivity.validUris.size(); i++) {
+            prefix = GameActivity.validUris.get(i).getHost().equals("") ?
+                    GameActivity.validUris.get(i).getScheme() + "://" :
+                    GameActivity.validUris.get(i).getScheme() + "://" + GameActivity.validUris.get(i).getHost() + "/";
+            if (input.startsWith(prefix)) {
+                inputSudoku = input.replace(prefix, "");
+                break;
+            }
+
+            String endOfRecord = i == GameActivity.validUris.size() - 1 ? "" : ", ";
+            errorMessage.append(prefix);
+            errorMessage.append(endOfRecord);
+        }
+
+        if (inputSudoku == null) {
+            Toast.makeText(MainActivity.this,
+                    this.getString(R.string.menu_import_wrong_format_custom_sudoku) + " " + errorMessage.toString(), Toast.LENGTH_LONG).show();
+            return;
+        }
+
+        double size = Math.sqrt(inputSudoku.length());
+        boolean validSize = false;
+
+        // check whether or not the size of the encoded sudoku is valid; if not, notify the user
+        for (GameType type : GameType.getValidGameTypes()) {
+            if (type.getSize() == size) {
+                validSize = true;
+                break;
+            }
+        }
+
+        if (!validSize) {
+            Toast.makeText(MainActivity.this, R.string.failed_to_verify_custom_sudoku_toast, Toast.LENGTH_LONG).show();
+            return;
+        }
+
+        GameType gameType = Enum.valueOf(GameType.class, "Default_" + (int)size + "x" + (int)size);
+
+        //check whether or not the sudoku is valid and has a unique solution
+        boolean solvable = CreateSudokuActivity.verify(gameType, inputSudoku);
+
+        // if the encoded sudoku is solvable, sent the code directly to the GameActivity; if not, notify the user
+        if (solvable) {
+            Toast.makeText(MainActivity.this, R.string.finished_verifying_custom_sudoku_toast, Toast.LENGTH_LONG).show();
+            final Intent intent = new Intent(this, GameActivity.class);
+            intent.setData(Uri.parse(prefix + inputSudoku));
+            startActivity(intent);
+            finish();
+        } else {
+            Toast.makeText(MainActivity.this, R.string.failed_to_verify_custom_sudoku_toast, Toast.LENGTH_LONG).show();
+        }
+    }
+
+    public void onDialogNegativeClick() {
+        mNavigationView.setCheckedItem(R.id.nav_newgame_main);
+    }
+
+    public static class ImportBoardDialog extends DialogFragment {
+        private LinkedList<IImportDialogFragmentListener> listeners = new LinkedList<>();
+
+        @Override
+        public void onAttach(Activity activity) {
+            super.onAttach(activity);
+            // Verify that the host activity implements the callback interface
+            if(activity instanceof IImportDialogFragmentListener) {
+                listeners.add((IImportDialogFragmentListener) activity);
+            }
+        }
+
+        @Override
+        public Dialog onCreateDialog(Bundle savedInstanceState) {
+            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(), R.style.AppTheme_Dialog);
+            LayoutInflater inflater = getActivity().getLayoutInflater();
+            DialogFragmentImportBoardBinding binding = DialogFragmentImportBoardBinding.inflate(inflater);
+            builder.setView(binding.getRoot());
+            builder.setMessage(R.string.dialog_import_custom_sudoku);
+            builder.setPositiveButton(R.string.dialog_import_custom_sudoku_positive_button, new DialogInterface.OnClickListener() {
+                public void onClick(DialogInterface dialog, int id) {
+                    for(IImportDialogFragmentListener l : listeners) {
+                        l.onImportDialogPositiveClick(binding.ver3ImportSudokuEditText.getText().toString());
+                    }
+                }
+            })
+                    .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
+                        public void onClick(DialogInterface dialog, int id) {
+                            for(IImportDialogFragmentListener l : listeners) {
+                                l.onDialogNegativeClick();
+                            }
+                        }
+                    });
+            return builder.create();
+        }
+
+    }
 
     /**
      * A {@link FragmentPagerAdapter} that returns a fragment corresponding to

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/PrefManager.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
 import android.content.Context;

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/SettingsActivity.java

@@ -1,192 +1,120 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
-
+import android.content.SharedPreferences;
-import android.annotation.TargetApi;
-import android.content.Context;
-import android.content.res.Configuration;
 import android.os.Build;
 import android.os.Bundle;
-import android.preference.ListPreference;
-import android.preference.Preference;
-import android.preference.PreferenceActivity;
-import androidx.appcompat.app.ActionBar;
 import android.preference.PreferenceFragment;
 import android.preference.PreferenceManager;
 import android.view.MenuItem;
-import android.view.View;
 
+import androidx.appcompat.app.ActionBar;
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.appcompat.app.AppCompatDelegate;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceFragmentCompat;
+import androidx.preference.PreferenceGroup;
+import androidx.preference.PreferenceScreen;
+
+import org.secuso.privacyfriendlysudoku.ui.SettingsActivity;
 import org.secuso.privacyfriendlysudoku.ui.view.R;
 
-import java.util.List;
+public class SettingsActivity extends AppCompatActivity {
-
-/**
- * A {@link PreferenceActivity} that presents a set of application settings. On
- * handset devices, settings are presented as a single list. On tablets,
- * settings are split by category, with category headers shown to the left of
- * the list of settings.
- * <p>
- * See <a href="http://developer.android.com/design/patterns/settings.html">
- * Android Design: Settings</a> for design guidelines and the <a
- * href="http://developer.android.com/guide/topics/ui/settings.html">Settings
- * API Guide</a> for more information on developing a Settings UI.
- */
-public class SettingsActivity extends AppCompatPreferenceActivity {
-    @Override
-    protected void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-        setupActionBar();
-
-        overridePendingTransition(0, 0);
-
-        View mainContent = findViewById(R.id.main_content);
-        if (mainContent != null) {
-            mainContent.setAlpha(0);
-            mainContent.animate().alpha(1).setDuration(BaseActivity.MAIN_CONTENT_FADEIN_DURATION);
-        }
-    }
-
-    /**
-     * Set up the {@link android.app.ActionBar}, if the API is available.
-     */
-    private void setupActionBar() {
-        ActionBar actionBar = getSupportActionBar();
-        if (actionBar != null) {
-            // Show the Up button in the action bar.
-            actionBar.setDisplayHomeAsUpEnabled(true);
-        }
-    }
-
-    @Override
-    public boolean onMenuItemSelected(int featureId, MenuItem item) {
-        int id = item.getItemId();
-        if (id == android.R.id.home) {
-            if (!super.onMenuItemSelected(featureId, item)) {
-                finish();
-                //NavUtils.navigateUpFromSameTask(this);
-            }
-            return true;
-        }
-        return super.onMenuItemSelected(featureId, item);
-    }
 
 
-    /**
+    private static SettingsFragment settingsFragment;
-     * {@inheritDoc}
-     */
-    @Override
-    public boolean onIsMultiPane() {
-        return isXLargeTablet(this);
-    }
 
-    /**
+    private static void recheckNightModeProperties(SharedPreferences sharedPreferences) {
-     * Helper method to determine if the device has an extra-large screen. For
-     * example, 10" tablets are extra-large.
-     */
-    private static boolean isXLargeTablet(Context context) {
-        return (context.getResources().getConfiguration().screenLayout
-                & Configuration.SCREENLAYOUT_SIZE_MASK) >= Configuration.SCREENLAYOUT_SIZE_XLARGE;
-    }
 
-    /**
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
-     * {@inheritDoc}
-     */
-    @Override
-    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
-    public void onBuildHeaders(List<Header> target) {
-        loadHeadersFromResource(R.xml.pref_settings_headers, target);
-    }
 
-    /**
+            if (sharedPreferences.getBoolean("pref_dark_mode_setting", false)) {
-     * A preference value change listener that updates the preference's summary
-     * to reflect its new value.
-     */
-    private static Preference.OnPreferenceChangeListener sBindPreferenceSummaryToValueListener = new Preference.OnPreferenceChangeListener() {
-        @Override
-        public boolean onPreferenceChange(Preference preference, Object value) {
-            String stringValue = value.toString();
-
-            if (preference instanceof ListPreference) {
-                // For list preferences, look up the correct display value in
-                // the preference's 'entries' list.
-                ListPreference listPreference = (ListPreference) preference;
-                int index = listPreference.findIndexOfValue(stringValue);
-
-                // Set the summary to reflect the new value.
-                preference.setSummary(
-                        index >= 0
-                                ? listPreference.getEntries()[index]
-                                : null);
 
+                settingsFragment.findPreference("pref_dark_mode_automatically_by_system").setEnabled(false);
+                settingsFragment.findPreference("pref_dark_mode_automatically_by_battery").setEnabled(false);
             } else {
-                // For all other preferences, set the summary to the value's
+                if (sharedPreferences.getBoolean("pref_dark_mode_automatically_by_battery", false) && sharedPreferences.getBoolean("pref_dark_mode_automatically_by_system", false) ) {
-                // simple string representation.
+                    sharedPreferences.edit().putBoolean("pref_dark_mode_automatically_by_battery", false).commit();
-                preference.setSummary(stringValue);
+                }
+
+                settingsFragment.findPreference("pref_dark_mode_automatically_by_system").setEnabled(!sharedPreferences.getBoolean("pref_dark_mode_automatically_by_battery", false));
+                settingsFragment.findPreference("pref_dark_mode_automatically_by_battery").setEnabled(!sharedPreferences.getBoolean("pref_dark_mode_automatically_by_system", false));
+            }}
+
+        if (sharedPreferences.getBoolean("pref_dark_mode_setting", false )) {
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_YES);
+
+        } else if (sharedPreferences.getBoolean("pref_dark_mode_automatically_by_system", false)) {
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM);
+        } else if(sharedPreferences.getBoolean("pref_dark_mode_automatically_by_battery", false)){
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_AUTO_BATTERY);
+        } else {
+            AppCompatDelegate.setDefaultNightMode(AppCompatDelegate.MODE_NIGHT_NO);
+        }
+    }
+
+    static SharedPreferences.OnSharedPreferenceChangeListener sharedPreferenceChangeListener = new SharedPreferences.OnSharedPreferenceChangeListener() {
+
+        @Override
+        public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String key) {
+            if (key.equals("pref_dark_mode_setting")|| key.equals("pref_dark_mode_automatically_by_system")||key.equals("pref_dark_mode_automatically_by_battery")) {
+                recheckNightModeProperties(sharedPreferences);
             }
-            return true;
         }
     };
 
-    /**
+    @Override
-     * Binds a preference's summary to its value. More specifically, when the
+    protected void onCreate(Bundle savedInstanceState) {
-     * preference's value is changed, its summary (line of text below the
+        super.onCreate(savedInstanceState);
-     * preference title) is updated to reflect the value. The summary is also
+        setContentView(R.layout.settings_activity);
-     * immediately updated upon calling this method. The exact display format is
+        settingsFragment = new SettingsFragment();
-     * dependent on the type of preference.
+        getSupportFragmentManager()
-     *
+                .beginTransaction()
-     * @see #sBindPreferenceSummaryToValueListener
+                .replace(R.id.settings, settingsFragment)
-     */
+                .commit();
-    private static void bindPreferenceSummaryToValue(Preference preference) {
+        ActionBar actionBar = getSupportActionBar();
-        // Set the listener to watch for value changes.
+        if (actionBar != null) {
-        preference.setOnPreferenceChangeListener(sBindPreferenceSummaryToValueListener);
+            actionBar.setDisplayHomeAsUpEnabled(true);
-
-        // Trigger the listener immediately with the preference's
-        // current value.
-        sBindPreferenceSummaryToValueListener.onPreferenceChange(preference,
-                PreferenceManager
-                        .getDefaultSharedPreferences(preference.getContext())
-                        .getString(preference.getKey(), ""));
-    }
-
-    /**
-     * This method stops fragment injection in malicious applications.
-     * Make sure to deny any unknown fragments here.
-     */
-    protected boolean isValidFragment(String fragmentName) {
-        return PreferenceFragment.class.getName().equals(fragmentName)
-                || GamePreferenceFragment.class.getName().equals(fragmentName);
-    }
-
-    /**
-     * This fragment shows general preferences only. It is used when the
-     * activity is showing a two-pane settings UI.
-     */
-    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
-    public static class GamePreferenceFragment extends PreferenceFragment {
-        @Override
-        public void onCreate(Bundle savedInstanceState) {
-            super.onCreate(savedInstanceState);
-            addPreferencesFromResource(R.xml.pref_settings_general);
-            setHasOptionsMenu(true);
-
-            // Bind the summaries of EditText/List/Dialog/Ringtone preferences
-            // to their values. When their values change, their summaries are
-            // updated to reflect the new value, per the Android Design
-            // guidelines.
-
-            //bindPreferenceSummaryToValue(findPreference("example_text"));
-            //bindPreferenceSummaryToValue(findPreference("example_list"));
-
         }
 
+
+
+    }
+    @Override
+    public boolean onOptionsItemSelected(MenuItem item) {
+        int id = item.getItemId();
+        if (id == android.R.id.home) {
+            finish();
+            return true;
+        }
+        return super.onOptionsItemSelected(item);
+    }
+
+
+    public static class SettingsFragment extends PreferenceFragmentCompat {
+
         @Override
-        public boolean onOptionsItemSelected(MenuItem item) {
+        public void onCreatePreferences(Bundle savedInstanceState, String rootKey) {
-            int id = item.getItemId();
+            setPreferencesFromResource(R.xml.pref_settings_general, rootKey);
-            if (id == android.R.id.home) {
+            SharedPreferences preferenceManager = PreferenceManager
-                getActivity().finish();
+                    .getDefaultSharedPreferences(getActivity());
-                //startActivity(new Intent(getActivity(), SettingsActivity.class));
+            preferenceManager.registerOnSharedPreferenceChangeListener(sharedPreferenceChangeListener);
-                return true;
+            recheckNightModeProperties(preferenceManager);
-            }
-            return super.onOptionsItemSelected(item);
         }
     }
-}
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/SplashActivity.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
 import android.content.Intent;

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/StatsActivity.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
 import android.content.Context;

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/TutorialActivity.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui;
 
 import android.content.Context;
@@ -20,7 +36,6 @@ import android.widget.TextView;
 
 import org.secuso.privacyfriendlysudoku.ui.view.R;
 
-
 /**
  * Class structure taken from tutorial at http://www.androidhive.info/2016/05/android-build-intro-slider-app/
  * @author Karola Marky

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/listener/IDeleteDialogFragmentListener.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.listener;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/listener/IFinalizeDialogFragmentListener.java

@@ -0,0 +1,22 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.secuso.privacyfriendlysudoku.ui.listener;
+
+public interface IFinalizeDialogFragmentListener {
+    public void onFinalizeDialogPositiveClick();
+    public void onDialogNegativeClick();
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/listener/IHintDialogFragmentListener.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.listener;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/listener/IImportDialogFragmentListener.java

@@ -0,0 +1,22 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.secuso.privacyfriendlysudoku.ui.listener;
+
+public interface IImportDialogFragmentListener {
+    public void onImportDialogPositiveClick(String input);
+    public void onDialogNegativeClick();
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/listener/IResetDialogFragmentListener.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.listener;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/listener/IShareDialogFragmentListener.java

@@ -0,0 +1,22 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.secuso.privacyfriendlysudoku.ui.listener;
+
+public interface IShareDialogFragmentListener {
+    public void onShareDialogPositiveClick(String input);
+    public void onDialogNegativeClick();
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/CellHighlightTypes.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.view;
 
 /**

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/CreateSudokuButtonType.java

@@ -0,0 +1,69 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.secuso.privacyfriendlysudoku.ui.view;
+
+import androidx.annotation.DrawableRes;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public enum CreateSudokuButtonType {
+    Unspecified(R.drawable.ic_accessibility_black_48dp),// placeholder
+    Value(R.drawable.ic_accessibility_black_48dp), // should be non picture
+    Do(R.drawable.ic_redo_black_48dp),
+    Undo(R.drawable.ic_undo_black_48dp),
+    Import(R.drawable.ic_import),
+    Spacer(R.drawable.ic_accessibility_black_48dp),//placeholder
+    Delete(R.drawable.ic_delete_black_48dp),
+    Finalize(R.drawable.ic_finalize),
+    Reset(R.drawable.ic_settings_backup_restore_black_48dp);
+
+
+    private int resID;
+
+    CreateSudokuButtonType(@DrawableRes int res){
+        this.resID = res;
+    }
+
+    public int getResID() {
+        return resID;
+    }
+
+    public static List<CreateSudokuButtonType> getSpecialButtons() {
+        ArrayList<CreateSudokuButtonType> result = new ArrayList<CreateSudokuButtonType>();
+        result.add(Undo);
+        result.add(Do);
+        result.add(Finalize);
+        //result.add(Spacer);
+        result.add(Delete);
+        result.add(Import);
+        return result;
+    }
+    public static String getName(CreateSudokuButtonType type) {
+        switch (type) {
+            case Do: return "Do";
+            case Undo: return "Un";
+            case Finalize: return "Fi";
+            case Import: return "Im";
+            case Spacer: return "";
+            case Delete: return "Del";
+            default:return "NotSet";
+        }
+    }
+}
+
+

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/CreateSudokuSpecialButton.java

@@ -0,0 +1,36 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.secuso.privacyfriendlysudoku.ui.view;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.widget.ImageButton;
+
+public class CreateSudokuSpecialButton extends androidx.appcompat.widget.AppCompatImageButton {
+    private int value = -1;
+    private CreateSudokuButtonType type = CreateSudokuButtonType.Unspecified;
+
+    public CreateSudokuSpecialButton(Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    public void setValue(int value)             { this.value = value; }
+    public void setType(CreateSudokuButtonType type)  { this.type = type; }
+    public int getValue ()                      { return value; }
+    public CreateSudokuButtonType getType()           { return type; }
+
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/CreateSudokuSpecialButtonLayout.java

@@ -0,0 +1,233 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.secuso.privacyfriendlysudoku.ui.view;
+
+import android.app.Activity;
+import android.app.AlertDialog;
+import android.app.Dialog;
+import android.app.DialogFragment;
+import android.app.FragmentManager;
+import android.content.Context;
+import android.content.DialogInterface;
+import android.graphics.Bitmap;
+import android.graphics.BitmapFactory;
+import android.graphics.Canvas;
+import android.graphics.drawable.Drawable;
+import android.os.Bundle;
+import android.util.AttributeSet;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.ImageView;
+import android.widget.LinearLayout;
+import android.widget.Toast;
+
+import androidx.core.content.ContextCompat;
+
+import org.secuso.privacyfriendlysudoku.controller.GameController;
+import org.secuso.privacyfriendlysudoku.game.listener.IHighlightChangedListener;
+import org.secuso.privacyfriendlysudoku.ui.GameActivity;
+import org.secuso.privacyfriendlysudoku.ui.MainActivity;
+import org.secuso.privacyfriendlysudoku.ui.listener.IFinalizeDialogFragmentListener;
+import org.secuso.privacyfriendlysudoku.ui.listener.IHintDialogFragmentListener;
+import org.secuso.privacyfriendlysudoku.ui.listener.IImportDialogFragmentListener;
+
+import java.util.LinkedList;
+
+import static org.secuso.privacyfriendlysudoku.ui.view.CreateSudokuButtonType.Spacer;
+import static org.secuso.privacyfriendlysudoku.ui.view.CreateSudokuButtonType.getSpecialButtons;
+
+public class CreateSudokuSpecialButtonLayout extends LinearLayout implements IHighlightChangedListener {
+
+    IFinalizeDialogFragmentListener finalizeDialogFragmentListener;
+    IImportDialogFragmentListener importDialogFragmentListener;
+    CreateSudokuSpecialButton[] fixedButtons;
+    public int fixedButtonsCount = getSpecialButtons().size();
+    GameController gameController;
+    SudokuKeyboardLayout keyboard;
+    Bitmap bitMap,bitResult;
+    Canvas canvas;
+    FragmentManager fragmentManager;
+    Context context;
+
+    OnClickListener listener = new OnClickListener() {
+        @Override
+        public void onClick(View v) {
+            if(v instanceof CreateSudokuSpecialButton) {
+                CreateSudokuSpecialButton btn = (CreateSudokuSpecialButton)v;
+
+                //int row = gameController.getSelectedRow();
+                //int col = gameController.getSelectedCol();
+
+                switch(btn.getType()) {
+                    case Delete:
+                        gameController.deleteSelectedCellsValue();
+                        break;
+                    case Import:
+                        MainActivity.ImportBoardDialog impDialog = new MainActivity.ImportBoardDialog();
+                        impDialog.show(fragmentManager, "ImportDialogFragment");
+                        break;
+                    case Do:
+                        gameController.ReDo();
+                        break;
+                    case Undo:
+                        gameController.UnDo();
+                        break;
+                    case Finalize:
+                        FinalizeConfirmationDialog dialog = new FinalizeConfirmationDialog();
+                        dialog.show(fragmentManager, "FinalizeDialogFragment");
+                    default:
+                        break;
+                }
+            }
+        }
+    };
+
+
+    public CreateSudokuSpecialButtonLayout(Context context, AttributeSet attrs) {
+        super(context, attrs);
+        setWeightSum(fixedButtonsCount);
+        this.context = context;
+    }
+
+    public void setButtonsEnabled(boolean enabled) {
+        for(CreateSudokuSpecialButton b : fixedButtons) {
+            b.setEnabled(enabled);
+        }
+    }
+
+    public void setButtons(int width, GameController gc, SudokuKeyboardLayout key, FragmentManager fm,
+                           int orientation, Context cxt, IFinalizeDialogFragmentListener finalizeListener,
+                           IImportDialogFragmentListener importListener) {
+        fragmentManager = fm;
+        keyboard=key;
+        gameController = gc;
+        context = cxt;
+        finalizeDialogFragmentListener = finalizeListener;
+        importDialogFragmentListener = importListener;
+        if(gameController != null) {
+            gameController.registerHighlightChangedListener(this);
+        }
+         fixedButtons = new CreateSudokuSpecialButton[fixedButtonsCount];
+        LayoutParams p;
+        int i = 0;
+        //ArrayList<SudokuButtonType> type = (ArrayList<SudokuButtonType>) SudokuButtonType.getSpecialButtons();
+        for (CreateSudokuButtonType t : getSpecialButtons()){
+            fixedButtons[i] = new CreateSudokuSpecialButton(getContext(),null);
+            if(orientation == LinearLayout.HORIZONTAL) {
+                p = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT, 1);
+            } else {
+                p = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT, 1);
+                fixedButtons[i].setPadding(25, 0, 25, 0);
+            }
+            p.setMargins(5, 5, 5, 5);
+
+            //int width2 =width/(fixedButtonsCount);
+            //p.width= width2-15;
+            if(t == Spacer) {
+                fixedButtons[i].setVisibility(View.INVISIBLE);
+            }
+            /*if(t == SudokuButtonType.Do && !gameController.isRedoAvailable()) {
+                fixedButtons[i].setEnabled(false);
+            }
+            if(t == SudokuButtonType.Undo && !gameController.isUndoAvailable()) {
+                fixedButtons[i].setEnabled(false);
+            }*/
+            fixedButtons[i].setLayoutParams(p);
+            fixedButtons[i].setType(t);
+            fixedButtons[i].setImageDrawable(getResources().getDrawable(t.getResID()));
+            // fixedButtons[i].setText(SudokuButtonType.getName(t));
+            fixedButtons[i].setScaleType(ImageView.ScaleType.CENTER);
+            fixedButtons[i].setAdjustViewBounds(true);
+            fixedButtons[i].setOnClickListener(listener);
+            fixedButtons[i].setBackgroundResource(R.drawable.numpad_highlighted_four);
+            addView(fixedButtons[i]);
+
+            if(fixedButtons[i].getVisibility() == View.VISIBLE) {
+                Drawable drawable = ContextCompat.getDrawable(context, fixedButtons[i].getType().getResID());
+                setUpVectorDrawable(drawable);
+                drawable.draw(canvas);
+                fixedButtons[i].setImageBitmap(bitResult);
+            }
+            i++;
+        }
+
+    }
+
+    @Override
+    public void onHighlightChanged() {
+        for(int i = 0; i < fixedButtons.length; i++) {
+            switch(fixedButtons[i].getType()) {
+                case Undo:
+                    fixedButtons[i].setBackgroundResource(gameController.isUndoAvailable() ?
+                            R.drawable.numpad_highlighted_four : R.drawable.inactive_button);
+                    break;
+                case Do:
+                    fixedButtons[i].setBackgroundResource(gameController.isRedoAvailable() ?
+                            R.drawable.numpad_highlighted_four : R.drawable.inactive_button);
+                    break;
+                default:
+                    break;
+            }
+        }
+    }
+
+    /*
+    Set up the vector drawables so that they can be properly displayed despite using theme attributes for their fill color
+     */
+    private void setUpVectorDrawable(Drawable drawable) {
+        drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());
+        bitMap = Bitmap.createBitmap(drawable.getIntrinsicWidth(),
+                drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
+        bitResult = Bitmap.createBitmap(bitMap.getWidth(), bitMap.getHeight(), Bitmap.Config.ARGB_8888);
+
+        canvas = new Canvas(bitResult);
+    }
+
+    public static class FinalizeConfirmationDialog extends DialogFragment {
+
+        LinkedList<IFinalizeDialogFragmentListener> listeners = new LinkedList<>();
+
+        @Override
+        public void onAttach(Activity activity) {
+            super.onAttach(activity);
+            // Verify that the host activity implements the callback interface
+            if(activity instanceof IFinalizeDialogFragmentListener) {
+                listeners.add((IFinalizeDialogFragmentListener) activity);
+            }
+        }
+
+        @Override
+        public Dialog onCreateDialog(Bundle savedInstanceState) {
+            // Use the Builder class for convenient dialog construction
+            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(), R.style.AppTheme_Dialog);
+            builder.setMessage(R.string.finalize_custom_sudoku_dialog)
+                    .setPositiveButton(R.string.okay, new DialogInterface.OnClickListener() {
+                        public void onClick(DialogInterface dialog, int id) {
+                            for(IFinalizeDialogFragmentListener l : listeners) {
+                                l.onFinalizeDialogPositiveClick();
+                            }
+                        }
+                    })
+                    .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
+                        public void onClick(DialogInterface dialog, int id) {
+                            // User cancelled the dialog
+                        }
+                    });
+            return builder.create();
+        }
+    }
+}

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuButton.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.view;
 
 import android.content.Context;
@@ -12,7 +28,7 @@ import android.widget.Button;
 
 
 
-public class SudokuButton extends Button {
+public class SudokuButton extends androidx.appcompat.widget.AppCompatButton {
 
     private int value = -1;
     private SudokuButtonType type = SudokuButtonType.Unspecified;

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuButtonType.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.view;
 
 import androidx.annotation.DrawableRes;

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuCellView.java

@@ -1,6 +1,24 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.view;
 
 import android.content.Context;
+import android.content.res.Configuration;
+import android.content.res.TypedArray;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Paint;
@@ -31,15 +49,32 @@ public class SudokuCellView extends View {
     Symbol symbolsToUse = Symbol.Default;
     RelativeLayout.LayoutParams params;
 
-
+    int backgroundColor;
-    public SudokuCellView(Context context) {
+    int backgroundErrorColor;
-        super(context);
+    int backgroundSelectedColor;
-    }
+    int backgroundConnectedOuterColor;
+    int backgroundConnectedInnerColor;
+    int backgroundValueHighlightedColor;
+    int backgroundValueHighlightedSelectedColor;
+    int textColor;
 
     public SudokuCellView(Context context, AttributeSet attrs){
         super(context, attrs);
+
+        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.SudokuCellView);
+        backgroundColor = a.getColor(R.styleable.SudokuCellView_sudokuCellBackgroundColor, Color.argb(255, 200, 200, 200));
+        backgroundErrorColor = a.getColor(R.styleable.SudokuCellView_sudokuCellBackgroundErrorColor, Color.argb(255, 200, 200, 200));
+        backgroundSelectedColor = a.getColor(R.styleable.SudokuCellView_sudokuCellBackgroundSelectedColor, Color.argb(255, 200, 200, 200));
+        backgroundConnectedOuterColor = a.getColor(R.styleable.SudokuCellView_sudokuCellBackgroundConnectedOuterColor, Color.argb(255, 200, 200, 200));
+        backgroundConnectedInnerColor = a.getColor(R.styleable.SudokuCellView_sudokuCellBackgroundConnectedInnerColor, Color.argb(255, 200, 200, 200));
+        backgroundValueHighlightedColor = a.getColor(R.styleable.SudokuCellView_sudokuCellBackgroundValueHighlightedColor, Color.argb(255, 200, 200, 200));
+        backgroundValueHighlightedSelectedColor = a.getColor(R.styleable.SudokuCellView_sudokuCellBackgroundValueHighlightedSelectedColor, Color.argb(255, 200, 200, 200));
+        textColor = a.getColor(R.styleable.SudokuCellView_sudokuCellTextColor, Color.argb(255, 200, 200, 200));
+        a.recycle();
     }
 
+
+
     public void setSelected(boolean b) {
         this.selected = b;
     }
@@ -89,13 +124,6 @@ public class SudokuCellView extends View {
         return true;
     }*/
 
-    @Override
-    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
-        super.onLayout(changed, left, top, right, bottom);
-
-
-    }
-
     @Override
     public void onDraw(Canvas canvas) {
         super.onDraw(canvas);
@@ -108,27 +136,28 @@ public class SudokuCellView extends View {
         Paint p = new Paint();
         switch(highlightType) {
             case Default:
-                p.setColor(Color.WHITE);
+                p.setColor(backgroundColor);
                 break;
             case Error:
-                p.setColor(Color.LTGRAY);
+                p.setColor(backgroundErrorColor);
                 break;
             case Selected:
-                p.setColor(Color.GREEN);
+                p.setColor(backgroundSelectedColor);
                 break;
             case Connected:
-                p.setColor(Color.WHITE);
+                p.setColor(backgroundConnectedOuterColor);
                 drawBackground(canvas, 3, 3, mWidth - 3, mHeight - 3, p);
-                p.setColor(Color.YELLOW);
+                p.setColor(backgroundConnectedInnerColor);
                 p.setAlpha(100);
                 break;
             case Value_Highlighted:
-                p.setColor(Color.YELLOW);
+                p.setColor(backgroundValueHighlightedColor);
                 break;
             case Value_Highlighted_Selected:
-                p.setColor(Color.CYAN);
+                p.setColor(backgroundValueHighlightedSelectedColor);
+                break;
             default:
-                p.setColor(Color.WHITE);
+                p.setColor(backgroundColor);
         }
 
 
@@ -147,6 +176,7 @@ public class SudokuCellView extends View {
 
     public void drawValue(Canvas canvas) {
         Paint p = new Paint();
+        p.setColor(textColor);
         int root = (int) Math.sqrt(size);
         int j= root+1;
         int k = root;

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuFieldLayout.java

@@ -1,7 +1,25 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.view;
 
 import android.content.Context;
 import android.content.SharedPreferences;
+import android.content.res.Configuration;
+import android.content.res.TypedArray;
 import android.graphics.Canvas;
 import android.graphics.Color;
 import android.graphics.Paint;
@@ -31,6 +49,9 @@ public class SudokuFieldLayout extends RelativeLayout implements IHighlightChang
     private int gameCellHeight;
     private SharedPreferences settings;
     private Paint p = new Paint();
+    int backgroundColor;
+    int errorColor;
+    int sectionLineColor;
 
     private OnTouchListener listener = new OnTouchListener() {
         @Override
@@ -55,8 +76,15 @@ public class SudokuFieldLayout extends RelativeLayout implements IHighlightChang
     public SudokuFieldLayout(Context context, AttributeSet attrs) {
         super(context, attrs);
         this.attrs=attrs;
+
+        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.SudokuFieldLayout);
+        backgroundColor = a.getColor(R.styleable.SudokuFieldLayout_sudokuFieldGridColor, Color.argb(255, 200, 200, 200));
+        errorColor = a.getColor(R.styleable.SudokuFieldLayout_sudokuFieldErrorColor, Color.RED);
+        sectionLineColor = a.getColor(R.styleable.SudokuFieldLayout_sudokuFieldSectionLineColor, Color.BLACK);
+        a.recycle();
+
         setWillNotDraw(false);
-        setBackgroundColor(Color.argb(255, 200, 200, 200));
+        setBackgroundColor(backgroundColor);
     }
 
     public void setSettingsAndGame(SharedPreferences sharedPref, GameController gc) {
@@ -98,7 +126,7 @@ public class SudokuFieldLayout extends RelativeLayout implements IHighlightChang
 
         if(gameController == null) return;
 
-        p.setColor(Color.BLACK);
+        p.setColor(sectionLineColor);
         p.setStrokeWidth(5);
 
         int horizontalSections = gameController.getSize() / sectionWidth;
@@ -222,7 +250,7 @@ public class SudokuFieldLayout extends RelativeLayout implements IHighlightChang
         p = new Paint(Paint.ANTI_ALIAS_FLAG);
         p.setStyle(Paint.Style.STROKE);
         p.setStrokeWidth(4);
-        p.setColor(Color.RED);
+        p.setColor(errorColor);
 
         float offsetX = 0;
         float offsetY = 0;

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuKeyboardLayout.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.view;
 
 import android.content.Context;

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuSpecialButton.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.view;
 
 import android.content.Context;
@@ -7,7 +23,7 @@ import android.widget.ImageButton;
 /**
  * Created by TMZ_LToP on 07.12.2015.
  */
-public class SudokuSpecialButton extends ImageButton {
+public class SudokuSpecialButton extends androidx.appcompat.widget.AppCompatImageButton {
     private int value = -1;
     private SudokuButtonType type = SudokuButtonType.Unspecified;
 

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuSpecialButtonLayout.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.view;
 
 import android.app.Activity;
@@ -10,6 +26,7 @@ import android.content.DialogInterface;
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
 import android.graphics.Canvas;
+import android.graphics.drawable.Drawable;
 import android.os.Bundle;
 import android.util.AttributeSet;
 import android.view.View;
@@ -18,8 +35,11 @@ import android.widget.ImageView;
 import android.widget.LinearLayout;
 import android.widget.Toast;
 
+import androidx.core.content.ContextCompat;
+
 import org.secuso.privacyfriendlysudoku.controller.GameController;
 import org.secuso.privacyfriendlysudoku.game.listener.IHighlightChangedListener;
+import org.secuso.privacyfriendlysudoku.ui.GameActivity;
 import org.secuso.privacyfriendlysudoku.ui.listener.IHintDialogFragmentListener;
 
 import java.util.LinkedList;
@@ -40,6 +60,7 @@ public class SudokuSpecialButtonLayout extends LinearLayout implements IHighligh
     Bitmap bitMap,bitResult;
     Canvas canvas;
     FragmentManager fragmentManager;
+    Context context;
 
     OnClickListener listener = new OnClickListener() {
         @Override
@@ -68,7 +89,7 @@ public class SudokuSpecialButtonLayout extends LinearLayout implements IHighligh
                         break;
                     case Hint:
                         if(gameController.isValidCellSelected()) {
-                            if(gameController.getUsedHints() == 0) {
+                            if(gameController.getUsedHints() == 0 && !gameController.gameIsCustom()) {
                                 // are you sure you want to use a hint?
                                 HintConfirmationDialog hintDialog = new HintConfirmationDialog();
                                 hintDialog.show(fragmentManager, "HintDialogFragment");
@@ -93,6 +114,7 @@ public class SudokuSpecialButtonLayout extends LinearLayout implements IHighligh
     public SudokuSpecialButtonLayout(Context context, AttributeSet attrs) {
         super(context, attrs);
         setWeightSum(fixedButtonsCount);
+        this.context = context;
     }
 
     public void setButtonsEnabled(boolean enabled) {
@@ -101,10 +123,11 @@ public class SudokuSpecialButtonLayout extends LinearLayout implements IHighligh
         }
     }
 
-    public void setButtons(int width, GameController gc, SudokuKeyboardLayout key, FragmentManager fm, int orientation) {
+    public void setButtons(int width, GameController gc, SudokuKeyboardLayout key, FragmentManager fm, int orientation, Context cxt) {
         fragmentManager = fm;
         keyboard=key;
         gameController = gc;
+        context = cxt;
         if(gameController != null) {
             gameController.registerHighlightChangedListener(this);
         }
@@ -142,6 +165,13 @@ public class SudokuSpecialButtonLayout extends LinearLayout implements IHighligh
             fixedButtons[i].setOnClickListener(listener);
             fixedButtons[i].setBackgroundResource(R.drawable.numpad_highlighted_four);
             addView(fixedButtons[i]);
+
+            if(fixedButtons[i].getVisibility() == View.VISIBLE) {
+                Drawable drawable = ContextCompat.getDrawable(context, fixedButtons[i].getType().getResID());
+                setUpVectorDrawable(drawable);
+                drawable.draw(canvas);
+                fixedButtons[i].setImageBitmap(bitResult);
+            }
             i++;
         }
 
@@ -160,12 +190,13 @@ public class SudokuSpecialButtonLayout extends LinearLayout implements IHighligh
                             R.drawable.numpad_highlighted_four : R.drawable.inactive_button);
                     break;
                 case NoteToggle:
-                    bitMap = BitmapFactory.decodeResource(getResources(), fixedButtons[i].getType().getResID());
+                    Drawable drawable = ContextCompat.getDrawable(context, fixedButtons[i].getType().getResID());
-                    bitResult = Bitmap.createBitmap(bitMap.getWidth(), bitMap.getHeight(), Bitmap.Config.ARGB_8888);
+                    // prepare canvas for the rotation of the note drawable
+                    setUpVectorDrawable(drawable);
 
-                    canvas = new Canvas(bitResult);
                     canvas.rotate(gameController.getNoteStatus() ? 45.0f : 0.0f, bitMap.getWidth()/2, bitMap.getHeight()/2);
                     canvas.drawBitmap(bitMap, 0, 0, null);
+                    drawable.draw(canvas);
 
                     fixedButtons[i].setImageBitmap(bitResult);
                     fixedButtons[i].setBackgroundResource(gameController.getNoteStatus() ? R.drawable.numpad_highlighted_three : R.drawable.numpad_highlighted_four);
@@ -179,6 +210,18 @@ public class SudokuSpecialButtonLayout extends LinearLayout implements IHighligh
         }
     }
 
+    /*
+    Set up the vector drawables so that they can be properly displayed despite using theme attributes for their fill color
+     */
+    private void setUpVectorDrawable(Drawable drawable) {
+        drawable.setBounds(0, 0, drawable.getIntrinsicWidth(), drawable.getIntrinsicHeight());
+        bitMap = Bitmap.createBitmap(drawable.getIntrinsicWidth(),
+                drawable.getIntrinsicHeight(), Bitmap.Config.ARGB_8888);
+        bitResult = Bitmap.createBitmap(bitMap.getWidth(), bitMap.getHeight(), Bitmap.Config.ARGB_8888);
+
+        canvas = new Canvas(bitResult);
+    }
+
     public static class HintConfirmationDialog extends DialogFragment {
 
         LinkedList<IHintDialogFragmentListener> listeners = new LinkedList<>();
@@ -195,7 +238,7 @@ public class SudokuSpecialButtonLayout extends LinearLayout implements IHighligh
         @Override
         public Dialog onCreateDialog(Bundle savedInstanceState) {
             // Use the Builder class for convenient dialog construction
-            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
+            AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(), R.style.AppTheme_Dialog);
             builder.setMessage(R.string.hint_confirmation)
                     .setPositiveButton(R.string.hint_confirmation_confirm, new DialogInterface.OnClickListener() {
                         public void onClick(DialogInterface dialog, int id) {

app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/WinDialog.java

@@ -1,3 +1,19 @@
+/*
+ This file is part of Privacy Friendly Sudoku.
+
+ Privacy Friendly Sudoku is free software:
+ you can redistribute it and/or modify it under the terms of the
+ GNU General Public License as published by the Free Software Foundation,
+ either version 3 of the License, or any later version.
+
+ Privacy Friendly Sudoku is distributed in the hope
+ that it will be useful, but WITHOUT ANY WARRANTY; without even
+ the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with Privacy Friendly Sudoku. If not, see <http://www.gnu.org/licenses/>.
+ */
 package org.secuso.privacyfriendlysudoku.ui.view;
 
 import android.app.AlertDialog;

app/src/main/res/drawable-v21/ic_info_black_24dp.xml

@@ -4,6 +4,6 @@
         android:viewportWidth="24.0"
         android:viewportHeight="24.0">
     <path
-            android:fillColor="#FF000000"
+            android:fillColor="?attr/standardVectorGraphic"
             android:pathData="M12,2C6.48,2 2,6.48 2,12s4.48,10 10,10 10,-4.48 10,-10S17.52,2 12,2zm1,15h-2v-6h2v6zm0,-8h-2V7h2v2z"/>
 </vector>

app/src/main/res/drawable-v21/ratingbar.xml

@@ -18,17 +18,17 @@
     <item android:id="@android:id/background">
         <bitmap
             android:src="@drawable/ic_star_black_48dp"
-            android:tint="@color/middlegrey" />
+            android:tint="?attr/rankingStarNotSelected" />
     </item>
     <item android:id="@android:id/secondaryProgress">
         <bitmap
             android:src="@drawable/ic_star_half_black_48dp"
-            android:tint="@color/middlegrey" />
+            android:tint="?attr/rankingStarNotSelected" />
     </item>
     <item android:id="@android:id/progress">
         <bitmap
             android:src="@drawable/ic_star_black_48dp"
-            android:tint="@color/colorAccent" />
+            android:tint="?attr/colorAccent" />
     </item>
 </layer-list>
 

app/src/main/res/drawable/create_game_src.xml

@@ -0,0 +1,4 @@
+<selector xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:state_checked="true" android:drawable="@drawable/ic_circle_blue_36dp"/>
+    <item android:state_checked="false" android:drawable="@drawable/ic_circle_grey_36dp"/>
+</selector>

app/src/main/res/drawable/ic_accessibility_black_48dp.xml

@@ -0,0 +1,14 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="192dp"
+    android:height="192dp"
+    android:viewportWidth="192"
+    android:viewportHeight="192">
+  <path
+      android:pathData="M89.5,17.4c-10.1,4.4 -12.5,17.8 -4.6,25.7 6.5,6.5 15.7,6.5 22.2,-0 12.4,-12.4 -1.5,-32.7 -17.6,-25.7z"
+      android:fillColor= "?attr/standardVectorGraphic"
+      android:strokeColor="?attr/standardVectorGraphic"/>
+  <path
+      android:pathData="M24,64l0,8 24,-0 24,-0 0,52 0,52 8,-0 8,-0 0,-24 0,-24 8,-0 8,-0 0,24 0,24 8,-0 8,-0 0,-52 0,-52 24,-0 24,-0 0,-8 0,-8 -72,-0 -72,-0 0,8z"
+      android:fillColor="?attr/standardVectorGraphic"
+      android:strokeColor="?attr/standardVectorGraphic"/>
+</vector>

app/src/main/res/drawable/ic_circle_blue_36dp.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="37dp"
+    android:height="37dp"
+    android:viewportWidth="24.0"
+    android:viewportHeight="24.0">
+    <path
+        android:fillColor="?attr/rankingCircleSelected"
+        android:pathData="M12,12m-10,0a10,10 0,1 1,20 0a10,10 0,1 1,-20 0"/>
+</vector>

app/src/main/res/drawable/ic_circle_grey_36dp.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="37dp"
+    android:height="37dp"
+    android:viewportWidth="24.0"
+    android:viewportHeight="24.0">
+    <path
+        android:fillColor="?attr/rankingCircleNotSelected"
+        android:pathData="M12,12m-10,0a10,10 0,1 1,20 0a10,10 0,1 1,-20 0"/>
+</vector>

app/src/main/res/drawable/ic_create_black_48dp.xml

@@ -0,0 +1,14 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="192dp"
+    android:height="192dp"
+    android:viewportWidth="192"
+    android:viewportHeight="192">
+  <path
+      android:pathData="M136.5,25.9c-1.6,1 -5.9,4.9 -9.5,8.5l-6.5,6.6 15,15 15,15 8.8,-8.8c6.8,-7 8.7,-9.5 8.7,-11.8 0,-2.3 -2.3,-5.1 -11.8,-14.6 -12.7,-12.7 -14.1,-13.4 -19.7,-9.9z"
+      android:fillColor="?attr/standardVectorGraphic"
+      android:strokeColor="?attr/standardVectorGraphic"/>
+  <path
+      android:pathData="M67.7,93.8l-43.7,43.7 0,15.3 0,15.2 14.8,-0 14.7,-0 44.5,-44.5 44.5,-44.5 -14.5,-14.5c-8,-8 -14.9,-14.5 -15.5,-14.5 -0.6,-0 -20.7,19.7 -44.8,43.8z"
+      android:fillColor="?attr/standardVectorGraphic"
+      android:strokeColor="?attr/standardVectorGraphic"/>
+</vector>

app/src/main/res/drawable/ic_delete_black_48dp.xml

@@ -0,0 +1,14 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="192dp"
+    android:height="192dp"
+    android:viewportWidth="192"
+    android:viewportHeight="192">
+  <path
+      android:pathData="M71.5,28l-3.9,4 -13.8,-0 -13.8,-0 0,8 0,8 56,-0 56,-0 0,-8 0,-8 -13.8,-0 -13.8,-0 -3.9,-4 -3.9,-4 -20.6,-0 -20.6,-0 -3.9,4z"
+      android:fillColor="?attr/standardVectorGraphic"
+      android:strokeColor="?attr/standardVectorGraphic"/>
+  <path
+      android:pathData="M48.2,106.9c0.3,49.7 0.4,51 2.4,53.7 1.1,1.5 3.3,3.7 4.8,4.8 2.7,2 3.9,2.1 40.6,2.1 36.7,-0 37.9,-0.1 40.6,-2.1 1.5,-1.1 3.7,-3.3 4.8,-4.8 2,-2.7 2.1,-4 2.4,-53.7l0.3,-50.9 -48.1,-0 -48.1,-0 0.3,50.9z"
+      android:fillColor="?attr/standardVectorGraphic"
+      android:strokeColor="?attr/standardVectorGraphic"/>
+</vector>

app/src/main/res/drawable/ic_finalize.xml

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="192dp"
+    android:height="192dp"
+    android:viewportWidth="192"
+    android:viewportHeight="192">
+  <path
+      android:pathData="M109,89.5l-30.5,30.5 -12,-12 -12.1,-12 -3.9,4 -3.9,4 16.2,16.3 16.2,16.2 34,-34c18.7,-18.7 34,-34.5 34,-35 0,-0.6 -1.7,-2.8 -3.8,-4.8l-3.7,-3.7 -30.5,30.5z"
+      android:fillColor="?attr/standardVectorGraphic"
+      android:strokeColor="?attr/standardVectorGraphic"/>
+</vector>

app/src/main/res/drawable/ic_import.xml

@@ -0,0 +1,4 @@
+<vector android:height="192dp" android:viewportHeight="24"
+    android:viewportWidth="24" android:width="192dp" xmlns:android="http://schemas.android.com/apk/res/android">
+    <path android:fillColor="?attr/standardVectorGraphic" android:pathData="m12 2v10l2 -2h1l2 2v-10zm-9 1v19h18v-19h-3v16h-12v-13h5v-3z"/>
+</vector>

app/src/main/res/drawable/ic_info_black_24dp.xml

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="36dp"
+    android:height="36dp"
+    android:viewportWidth="36"
+    android:viewportHeight="36">
+  <path
+      android:pathData="M11.2,4.7c-7.1,3.5 -10.2,13.3 -6.4,20.3 2.3,4.2 8.4,8 13,8 7.9,-0 15.2,-7.3 15.2,-15.2 -0.1,-10.6 -12.1,-17.9 -21.8,-13.1zM19,12c0,0.5 -0.4,1 -1,1 -0.5,-0 -1,-0.5 -1,-1 0,-0.6 0.5,-1 1,-1 0.6,-0 1,0.4 1,1zM19,21c0,2.2 -0.4,4 -1,4 -0.5,-0 -1,-1.8 -1,-4 0,-2.2 0.5,-4 1,-4 0.6,-0 1,1.8 1,4z"
+      android:fillColor="?attr/standardVectorGraphic"
+      android:strokeColor="?attr/standardVectorGraphic"/>
+</vector>

app/src/main/res/drawable/ic_keyboard_arrow_left_black_24dp.xml

@@ -4,6 +4,6 @@
         android:viewportWidth="24.0"
         android:viewportHeight="24.0">
     <path
-        android:fillColor="#FF000000"
+        android:fillColor="?attr/standardVectorGraphic"
         android:pathData="M15.41,16.09l-4.58,-4.59 4.58,-4.59L14,5.5l-6,6 6,6z"/>
 </vector>

app/src/main/res/drawable/ic_keyboard_arrow_right_black_24dp.xml

@@ -4,6 +4,6 @@
         android:viewportWidth="24.0"
         android:viewportHeight="24.0">
     <path
-        android:fillColor="#FF000000"
+        android:fillColor="?attr/standardVectorGraphic"
         android:pathData="M8.59,16.34l4.58,-4.59 -4.58,-4.59L10,5.75l6,6 -6,6z"/>
 </vector>

app/src/main/res/drawable/ic_launcher_foreground.xml

@@ -5,32 +5,32 @@
     android:viewportHeight="512">
   <path
       android:pathData="M174.65,41.63h13.43v429.87h-13.43z"
-      android:fillColor="#fff"/>
+      android:fillColor="?attr/lightestBackGround"/>
   <path
       android:pathData="M322.42,41.63h13.43v429.87h-13.43z"
-      android:fillColor="#fff"/>
+      android:fillColor="?attr/lightestBackGround"/>
   <path
       android:pathData="M40.31,337.17l0,-13.43l429.87,-0l0,13.43z"
-      android:fillColor="#fff"/>
+      android:fillColor="?attr/lightestBackGround"/>
   <path
       android:pathData="M40.31,189.4l0,-13.43l429.87,-0l0,13.43z"
-      android:fillColor="#fff"/>
+      android:fillColor="?attr/lightestBackGround"/>
   <path
       android:pathData="M94.05,68.49h40.3V55.06H94.05a26.87,26.87 0,0 0,0 53.73h13.43a13.44,13.44 0,1 1,0 26.87H67.18v13.43h40.3a26.87,26.87 0,0 0,0 -53.73H94.05a13.44,13.44 0,0 1,0 -26.87Z"
-      android:fillColor="#fff"/>
+      android:fillColor="?attr/lightestBackGround"/>
   <path
       android:pathData="M262,206.19h-40.3v94L262,300.19a26.86,26.86 0,0 0,26.86 -26.87v-40.3A26.86,26.86 0,0 0,262 206.19ZM262,286.79L235.1,286.79L235.1,219.62L262,219.62a13.43,13.43 0,0 1,13.43 13.43v40.3A13.43,13.43 0,0 1,262 286.79Z"
-      android:fillColor="#fff"/>
+      android:fillColor="?attr/lightestBackGround"/>
   <path
       android:pathData="M406.38,206.19L392.94,206.19a26.86,26.86 0,0 0,-26.86 26.86v40.3a26.86,26.86 0,0 0,26.86 26.87h13.44a26.87,26.87 0,0 0,26.86 -26.87v-40.3A26.87,26.87 0,0 0,406.38 206.19ZM419.81,273.35a13.48,13.48 0,0 1,-13.43 13.44L392.94,286.79a13.47,13.47 0,0 1,-13.43 -13.44v-40.3a13.47,13.47 0,0 1,13.43 -13.43h13.44a13.48,13.48 0,0 1,13.43 13.43Z"
-      android:fillColor="#fff"/>
+      android:fillColor="?attr/lightestBackGround"/>
   <path
       android:pathData="M134.35,374.01l0,0l0,0l0,0l0,-9.5l-9.36,0l-0.04,0.1l-0.1,-0.1l-37.91,37.91l-6.32,6.32l0,-12.56l0,-31.67l-13.44,0l0,19.82l0,17.34l0,20.51l0,17.64l0,18.72l13.44,0l0,-30.8l6.45,-6.45l37.78,37.25l0,0l9.5,0l0,-9.36l-37.85,-37.33l37.84,-37.84l0.01,0z"
-      android:fillColor="#fff"/>
+      android:fillColor="?attr/lightestBackGround"/>
   <path
       android:pathData="M275.4,58.42v60.45a20.15,20.15 0,1 1,-40.3 0V58.42H221.67v60.45a33.58,33.58 0,1 0,67.16 0V58.42Z"
-      android:fillColor="#fff"/>
+      android:fillColor="?attr/lightestBackGround"/>
   <path
       android:pathData="M275.4,364.51V425a20.15,20.15 0,1 1,-40.3 0V364.51H221.67V425a33.58,33.58 0,1 0,67.16 0V364.51Z"
-      android:fillColor="#fff"/>
+      android:fillColor="?attr/lightestBackGround"/>
 </vector>

app/src/main/res/drawable/ic_launcher_foreground_shadow.xml

@@ -2,16 +2,16 @@
     xmlns:aapt="http://schemas.android.com/aapt"
     android:width="512dp"
     android:height="512dp"
-    android:viewportWidth="512"
+    android:viewportWidth="600"
-    android:viewportHeight="512">
+    android:viewportHeight="600">
   <path
-      android:pathData="M510.91,471.7V216.47L336.27,41.83H323.68V93.05L289.26,58.62H275.82v40.3l-40.3,-40.3H222.09l0,16.77L188.51,41.83H175.07l0.12,54.69L134.35,55.68 88.6,62 71.8,76.25l2.52,17.64 5,6.71 -5.88,-0.84 38.62,38.62 -44.49,-2.52V149.3l27,27 -53.83,-0.1V189.6L174.23,323.09H40.74v14.28l26.87,26.86v94L121.34,512H470.61A40.42,40.42 0,0 0,510.91 471.7Z">
+      android:pathData="M659,552.9V364.5L336.3,41.8h-12.6V93l-34.4,-34.4h-13.4v40.3l-40.3,-40.3h-13.4v16.8l-33.6,-33.6h-13.4l0.1,54.7l-40.8,-40.8L88.6,62L71.8,76.2l2.5,17.6l5,6.7l-5.9,-0.8l38.6,38.6l-44.5,-2.5v13.4l27,27l-53.8,-0.1v13.4l133.5,133.5H40.7v14.3l26.9,26.9v94l141.5,141.6L633,611.9C655.2,611.8 658.9,575.1 659,552.9z">
     <aapt:attr name="android:fillColor">
       <gradient 
-          android:startY="43.94"
+          android:startY="30.4022"
-          android:startX="119.85"
+          android:startX="143.3293"
-          android:endY="551.52"
+          android:endY="680.6151"
-          android:endX="412.9"
+          android:endX="518.728"
           android:type="linear">
         <item android:offset="0" android:color="#FF004492"/>
         <item android:offset="0.22" android:color="#F9004593"/>
@@ -25,33 +25,33 @@
     </aapt:attr>
   </path>
   <path
-      android:pathData="M174.65,41.63h13.43v429.87h-13.43z"
+      android:pathData="M174.6,41.6h13.4v429.9h-13.4z"
-      android:fillColor="#fff"/>
+      android:fillColor="#FFFFFF"/>
   <path
-      android:pathData="M322.42,41.63h13.43v429.87h-13.43z"
+      android:pathData="M322.4,41.6h13.4v429.9h-13.4z"
-      android:fillColor="#fff"/>
+      android:fillColor="#FFFFFF"/>
   <path
-      android:pathData="M40.31,337.17l0,-13.43l429.87,-0l0,13.43z"
+      android:pathData="M40.3,323.7h429.9v13.4h-429.9z"
-      android:fillColor="#fff"/>
+      android:fillColor="#FFFFFF"/>
   <path
-      android:pathData="M40.31,189.4l0,-13.43l429.87,-0l0,13.43z"
+      android:pathData="M40.3,176h429.9v13.4h-429.9z"
-      android:fillColor="#fff"/>
+      android:fillColor="#FFFFFF"/>
   <path
-      android:pathData="M94.05,68.49h40.3V55.06H94.05a26.87,26.87 0,0 0,0 53.73h13.43a13.44,13.44 0,1 1,0 26.87H67.18v13.43h40.3a26.87,26.87 0,0 0,0 -53.73H94.05a13.44,13.44 0,0 1,0 -26.87Z"
+      android:pathData="M94.1,68.5h40.3V55.1H94.1c-14.8,0.3 -26.6,12.5 -26.3,27.4c0.3,14.4 11.9,26.1 26.3,26.3h13.4c7.4,-0.2 13.6,5.6 13.8,13.1c0.2,7.4 -5.6,13.6 -13.1,13.8c-0.2,0 -0.5,0 -0.7,0H67.2v13.4h40.3c14.8,-0.3 26.6,-12.5 26.3,-27.4c-0.3,-14.4 -11.9,-26.1 -26.3,-26.3H94.1C86.6,95.2 80.8,89 81,81.6C81.2,74.4 86.9,68.7 94.1,68.5z"
-      android:fillColor="#fff"/>
+      android:fillColor="#FFFFFF"/>
   <path
-      android:pathData="M262,206.19h-40.3v94L262,300.19a26.86,26.86 0,0 0,26.86 -26.87v-40.3A26.86,26.86 0,0 0,262 206.19ZM262,286.79L235.1,286.79L235.1,219.62L262,219.62a13.43,13.43 0,0 1,13.43 13.43v40.3A13.43,13.43 0,0 1,262 286.79Z"
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-      android:fillColor="#fff"/>
+      android:fillColor="#FFFFFF"/>
 </vector>

app/src/main/res/drawable/ic_launcher_foreground_shadow_old.xml

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+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:aapt="http://schemas.android.com/aapt"
+    android:width="512dp"
+    android:height="512dp"
+    android:viewportWidth="512"
+    android:viewportHeight="512">
+  <path
+      android:pathData="M510.91,471.7V216.47L336.27,41.83H323.68V93.05L289.26,58.62H275.82v40.3l-40.3,-40.3H222.09l0,16.77L188.51,41.83H175.07l0.12,54.69L134.35,55.68 88.6,62 71.8,76.25l2.52,17.64 5,6.71 -5.88,-0.84 38.62,38.62 -44.49,-2.52V149.3l27,27 -53.83,-0.1V189.6L174.23,323.09H40.74v14.28l26.87,26.86v94L121.34,512H470.61A40.42,40.42 0,0 0,510.91 471.7Z">
+    <aapt:attr name="android:fillColor">
+      <gradient 
+          android:startY="43.94"
+          android:startX="119.85"
+          android:endY="551.52"
+          android:endX="412.9"
+          android:type="linear">
+        <item android:offset="0" android:color="#FF004492"/>
+        <item android:offset="0.22" android:color="#F9004593"/>
+        <item android:offset="0.39" android:color="#E8024894"/>
+        <item android:offset="0.55" android:color="#C9044E97"/>
+        <item android:offset="0.7" android:color="#A007569B"/>
+        <item android:offset="0.84" android:color="#6B0A60A0"/>
+        <item android:offset="0.97" android:color="#280F6CA6"/>
+        <item android:offset="1" android:color="#19106FA8"/>
+      </gradient>
+    </aapt:attr>
+  </path>
+  <path
+      android:pathData="M174.65,41.63h13.43v429.87h-13.43z"
+      android:fillColor="#fff"/>
+  <path
+      android:pathData="M322.42,41.63h13.43v429.87h-13.43z"
+      android:fillColor="#fff"/>
+  <path
+      android:pathData="M40.31,337.17l0,-13.43l429.87,-0l0,13.43z"
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+  <path
+      android:pathData="M40.31,189.4l0,-13.43l429.87,-0l0,13.43z"
+      android:fillColor="#fff"/>
+  <path
+      android:pathData="M94.05,68.49h40.3V55.06H94.05a26.87,26.87 0,0 0,0 53.73h13.43a13.44,13.44 0,1 1,0 26.87H67.18v13.43h40.3a26.87,26.87 0,0 0,0 -53.73H94.05a13.44,13.44 0,0 1,0 -26.87Z"
+      android:fillColor="#fff"/>
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+      android:fillColor="#fff"/>
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+      android:pathData="M134.35,374.01l0,0l0,0l0,0l0,-9.5l-9.36,0l-0.04,0.1l-0.1,-0.1l-37.91,37.91l-6.32,6.32l0,-12.56l0,-31.67l-13.44,0l0,19.82l0,17.34l0,20.51l0,17.64l0,18.72l13.44,0l0,-30.8l6.45,-6.45l37.78,37.25l0,0l9.5,0l0,-9.36l-37.85,-37.33l37.84,-37.84l0.01,0z"
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+      android:fillColor="#fff"/>
+</vector>

app/src/main/res/drawable/ic_lightbulb_outline_black_48dp.xml

@@ -0,0 +1,14 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="192dp"
+    android:height="192dp"
+    android:viewportWidth="192"
+    android:viewportHeight="192">
+  <path
+      android:pathData="M84.5,17.2c-9,1.6 -20.7,8.1 -27.9,15.4 -22.3,22.2 -21.8,57.6 1.1,80l6.3,6.1 0,10.2c0,9.5 0.2,10.4 2.5,12.6l2.4,2.5 27.1,-0 27.1,-0 2.4,-2.5c2.3,-2.2 2.5,-3.1 2.5,-12.6l0,-10.2 6.3,-6.1c23,-22.4 23.4,-57.6 1.1,-80 -13.4,-13.4 -31.9,-19 -50.9,-15.4zM113.6,36.4c8.6,4.3 14.3,10.2 18.8,19.6 2.8,5.9 3.1,7.4 3.1,16 0,8.3 -0.4,10.3 -2.8,15.4 -3.6,7.7 -8.1,13.1 -15.1,18.1l-5.6,4 0,9.2 0,9.3 -16,-0 -16,-0 0,-9.3 0,-9.2 -5.1,-3.5c-7,-4.7 -11.6,-10.1 -15.3,-17.9 -2.8,-6 -3.1,-7.5 -3.1,-16.1 0,-8.6 0.3,-10.1 3.2,-16.2 4,-8.5 9.7,-14.7 17.2,-18.6 7.9,-4.3 12.2,-5.2 21.5,-4.7 6.6,0.3 9.1,0.9 15.2,3.9z"
+      android:fillColor="?attr/standardVectorGraphic"
+      android:strokeColor="?attr/standardVectorGraphic"/>
+  <path
+      android:pathData="M72,165.5c0,4.6 0.4,6 2.5,8 2.4,2.5 2.6,2.5 21.5,2.5 18.9,-0 19.1,-0 21.5,-2.5 2.1,-2 2.5,-3.4 2.5,-8l0,-5.5 -24,-0 -24,-0 0,5.5z"
+      android:fillColor="?attr/standardVectorGraphic"
+      android:strokeColor="?attr/standardVectorGraphic"/>
+</vector>

app/src/main/res/drawable/ic_menu_about.xml

@@ -4,6 +4,6 @@
     android:viewportWidth="24.0"
     android:viewportHeight="24.0">
     <path
-        android:fillColor="#FF000000"
+        android:fillColor="?attr/standardVectorGraphic"
         android:pathData="M11,17h2v-6h-2v6zM12,2C6.48,2 2,6.48 2,12s4.48,10 10,10 10,-4.48 10,-10S17.52,2 12,2zM12,20c-4.41,0 -8,-3.59 -8,-8s3.59,-8 8,-8 8,3.59 8,8 -3.59,8 -8,8zM11,9h2L13,7h-2v2z"/>
 </vector>

app/src/main/res/drawable/ic_menu_daily_sudoku.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0">
+    <path
+        android:fillColor="?attr/standardVectorGraphic"
+        android:pathData="M11.99,2C6.47,2 2,6.48 2,12s4.47,10 9.99,10C17.52,22 22,17.52 22,12S17.52,2 11.99,2zM12,20c-4.42,0 -8,-3.58 -8,-8s3.58,-8 8,-8 8,3.58 8,8 -3.58,8 -8,8zM12.5,7H11v6l5.25,3.15 0.75,-1.23 -4.5,-2.67z"/>
+</vector>

app/src/main/res/drawable/ic_menu_help.xml

@@ -4,6 +4,6 @@
     android:viewportWidth="24.0"
     android:viewportHeight="24.0">
     <path
-        android:fillColor="#FF000000"
+        android:fillColor="?attr/standardVectorGraphic"
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 </vector>

app/src/main/res/drawable/ic_menu_home.xml

@@ -4,6 +4,6 @@
     android:viewportWidth="24.0"
     android:viewportHeight="24.0">
     <path
-        android:fillColor="#FF000000"
+        android:fillColor="?attr/standardVectorGraphic"
         android:pathData="M10,20v-6h4v6h5v-8h3L12,3 2,12h3v8z"/>
 </vector>