diff --git a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/GameActivity.java b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/GameActivity.java
index 31a5f0d..6c1d319 100644
--- a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/GameActivity.java
+++ b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/GameActivity.java
@@ -362,7 +362,8 @@ public class GameActivity extends BaseActivity implements NavigationView.OnNavig
         ratingBar.setMax(numberOfStarts);
         ratingBar.setNumStars(numberOfStarts);
         ratingBar.setRating(difficutyList.indexOf(gameController.getDifficulty()) + 1);
-        ((TextView)findViewById(R.id.difficultyText)).setText(getString(gameController.getDifficulty().getStringResID()));
+        TextView diffText = ((TextView)findViewById(R.id.difficultyText));
+        diffText.setText(getString(gameController.getDifficulty().getStringResID()));
 
 
         DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
diff --git a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/MainActivity.java b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/MainActivity.java
index be2b943..08b1078 100644
--- a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/MainActivity.java
+++ b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/MainActivity.java
@@ -161,6 +161,7 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
         difficultyBar.setNumStars(difficultyList.size());
         difficultyBar.setMax(difficultyList.size());
         CheckBox createGameBar = (CheckBox) findViewById(R.id.circleButton);
+        createGameBar.setButtonDrawable(R.drawable.create_game_src);
         difficultyBar.setOnRatingBarChangeListener(new RatingBar.OnRatingBarChangeListener() {
             @Override
             public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) {
@@ -177,16 +178,14 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
             }
         });
 
-        createGameBar.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
+        createGameBar.setOnClickListener(new View.OnClickListener() {
             @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);
-            }});
+            public void onClick(View v) {
+                difficultyBar.setRating(0);
+                ((Button)findViewById(R.id.playButton)).setText(R.string.create_game);
+                createGameBar.setChecked(true);
+            }
+        });
 
         String retrievedDifficulty = settings.getString("lastChosenDifficulty", "Moderate");
         GameDifficulty lastChosenDifficulty = GameDifficulty.valueOf(
@@ -320,10 +319,10 @@ public class MainActivity extends BaseActivity implements NavigationView.OnNavig
         List<GameInfoContainer> gic = fm.loadGameStateInfo();
         if(gic.size() > 0 && !(gic.size() == 1 && gic.get(0).getID() == GameController.DAILY_SUDOKU_ID)) {
             continueButton.setEnabled(true);
-            continueButton.setBackgroundResource(R.drawable.standalone_button);
+            continueButton.setBackgroundResource(R.drawable.button_standalone);
         } else {
             continueButton.setEnabled(false);
-            continueButton.setBackgroundResource(R.drawable.inactive_button);
+            continueButton.setBackgroundResource(R.drawable.button_inactive);
         }
     }
 
diff --git a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/TutorialActivity.java b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/TutorialActivity.java
index 609d750..5313c8e 100644
--- a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/TutorialActivity.java
+++ b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/TutorialActivity.java
@@ -31,6 +31,7 @@ import android.view.ViewGroup;
 import android.view.Window;
 import android.view.WindowManager;
 import android.widget.Button;
+import android.widget.CheckBox;
 import android.widget.LinearLayout;
 import android.widget.TextView;
 
@@ -212,6 +213,11 @@ public class TutorialActivity extends AppCompatActivity {
             View view = layoutInflater.inflate(layouts[position], container, false);
             container.addView(view);
 
+            CheckBox createGameBar = (CheckBox) findViewById(R.id.circleButton);
+            if(createGameBar != null) {
+                createGameBar.setButtonDrawable(R.drawable.create_game_src);
+            }
+
             return view;
         }
 
diff --git a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/CreateSudokuSpecialButtonLayout.java b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/CreateSudokuSpecialButtonLayout.java
index 0a92c1e..299cca3 100644
--- a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/CreateSudokuSpecialButtonLayout.java
+++ b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/CreateSudokuSpecialButtonLayout.java
@@ -24,7 +24,6 @@ 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;
@@ -33,16 +32,13 @@ 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;
@@ -173,11 +169,11 @@ public class CreateSudokuSpecialButtonLayout extends LinearLayout implements IHi
             switch(fixedButtons[i].getType()) {
                 case Undo:
                     fixedButtons[i].setBackgroundResource(gameController.isUndoAvailable() ?
-                            R.drawable.numpad_highlighted_four : R.drawable.inactive_button);
+                            R.drawable.numpad_highlighted_four : R.drawable.button_inactive);
                     break;
                 case Do:
                     fixedButtons[i].setBackgroundResource(gameController.isRedoAvailable() ?
-                            R.drawable.numpad_highlighted_four : R.drawable.inactive_button);
+                            R.drawable.numpad_highlighted_four : R.drawable.button_inactive);
                     break;
                 default:
                     break;
diff --git a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuSpecialButtonLayout.java b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuSpecialButtonLayout.java
index b676b89..bf01a21 100644
--- a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuSpecialButtonLayout.java
+++ b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuSpecialButtonLayout.java
@@ -24,7 +24,6 @@ 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;
@@ -39,7 +38,6 @@ 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;
@@ -183,11 +181,11 @@ public class SudokuSpecialButtonLayout extends LinearLayout implements IHighligh
             switch(fixedButtons[i].getType()) {
                 case Undo:
                     fixedButtons[i].setBackgroundResource(gameController.isUndoAvailable() ?
-                            R.drawable.numpad_highlighted_four : R.drawable.inactive_button);
+                            R.drawable.numpad_highlighted_four : R.drawable.button_inactive);
                     break;
                 case Do:
                     fixedButtons[i].setBackgroundResource(gameController.isRedoAvailable() ?
-                            R.drawable.numpad_highlighted_four : R.drawable.inactive_button);
+                            R.drawable.numpad_highlighted_four : R.drawable.button_inactive);
                     break;
                 case NoteToggle:
                     Drawable drawable = ContextCompat.getDrawable(context, fixedButtons[i].getType().getResID());
diff --git a/app/src/main/res/drawable/ic_trophy_award_black_48dp.xml b/app/src/main/res/drawable-night-v21/ic_trophy_award_black_48dp.xml
similarity index 100%
rename from app/src/main/res/drawable/ic_trophy_award_black_48dp.xml
rename to app/src/main/res/drawable-night-v21/ic_trophy_award_black_48dp.xml
diff --git a/app/src/main/res/drawable/ic_trophy_black_48dp.xml b/app/src/main/res/drawable-night-v21/ic_trophy_black_48dp.xml
similarity index 100%
rename from app/src/main/res/drawable/ic_trophy_black_48dp.xml
rename to app/src/main/res/drawable-night-v21/ic_trophy_black_48dp.xml
diff --git a/app/src/main/res/drawable-night-v21/numpad_highlighted_four.xml b/app/src/main/res/drawable-night-v21/numpad_highlighted_four.xml
new file mode 100644
index 0000000..87ce8d9
--- /dev/null
+++ b/app/src/main/res/drawable-night-v21/numpad_highlighted_four.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <gradient
+        android:endColor="?attr/activeButtonColor"
+        android:startColor="?attr/activeButtonColor" />
+    <corners android:radius="6dp" />
+    <stroke
+        android:width="10px"
+        android:color="?attr/standardVectorGraphic" />
+</shape>
\ No newline at end of file
diff --git a/app/src/main/res/drawable-night/ic_trophy_award_black_48dp.png b/app/src/main/res/drawable-night/ic_trophy_award_black_48dp.png
new file mode 100644
index 0000000..92d66b7
Binary files /dev/null and b/app/src/main/res/drawable-night/ic_trophy_award_black_48dp.png differ
diff --git a/app/src/main/res/drawable-night/ic_trophy_black_48dp.png b/app/src/main/res/drawable-night/ic_trophy_black_48dp.png
new file mode 100644
index 0000000..46f2e92
Binary files /dev/null and b/app/src/main/res/drawable-night/ic_trophy_black_48dp.png differ
diff --git a/app/src/main/res/drawable-night/numpad_highlighted_four.xml b/app/src/main/res/drawable-night/numpad_highlighted_four.xml
new file mode 100644
index 0000000..29b7638
--- /dev/null
+++ b/app/src/main/res/drawable-night/numpad_highlighted_four.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <gradient
+        android:endColor="@color/lightblue"
+        android:startColor="@color/lightblue" />
+    <corners android:radius="6dp" />
+    <stroke
+        android:width="10px"
+        android:color="@color/white" />
+</shape>
\ No newline at end of file
diff --git a/app/src/main/res/drawable/inactive_button.xml b/app/src/main/res/drawable-v21/button_inactive.xml
similarity index 100%
rename from app/src/main/res/drawable/inactive_button.xml
rename to app/src/main/res/drawable-v21/button_inactive.xml
diff --git a/app/src/main/res/drawable/standalone_button.xml b/app/src/main/res/drawable-v21/button_standalone.xml
similarity index 100%
rename from app/src/main/res/drawable/standalone_button.xml
rename to app/src/main/res/drawable-v21/button_standalone.xml
diff --git a/app/src/main/res/drawable-v21/ic_trophy_award_black_48dp.xml b/app/src/main/res/drawable-v21/ic_trophy_award_black_48dp.xml
new file mode 100644
index 0000000..8dfe2b4
--- /dev/null
+++ b/app/src/main/res/drawable-v21/ic_trophy_award_black_48dp.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:fillColor="?attr/standardVectorGraphic"
+        android:name="Color Fill 1"
+        android:pathData="m96 18 -15 38 -42 3 32 27 -11 41 36 -29 36 29 -11 -41 32 -27 -42 -3 -15 -38zm0 103 -8 7v25h-11l-3 1l-2 1l-2 1l-1 1l-1 1l-1 1l-1 2l-1 2l-1 4v10h64v-10l-1 -4l-1 -2l-1 -2l-1 -1l-1 -1l-1 -1l-2 -1l-2 -1l-3 -1h-11v-25l-8 -7z" />
+</vector>
diff --git a/app/src/main/res/drawable-v21/ic_trophy_black_48dp.xml b/app/src/main/res/drawable-v21/ic_trophy_black_48dp.xml
new file mode 100644
index 0000000..844b657
--- /dev/null
+++ b/app/src/main/res/drawable-v21/ic_trophy_black_48dp.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:fillColor="?attr/standardVectorGraphic"
+        android:name="Shape 1"
+        android:pathData="m48 32v56h-16v-56zm112 0v56h-16v-56zm-144 -16c0 0 0 1.52 0 4.13c0 15.29 0 67.88 0 67.88c0.06 0.25 0.13 0.25 0.13 0.25c0 7.53 8.9 13.72 14.75 15.45c0.1 0.03 0.2 0.06 0.3 0.09c0.11 0.03 0.22 0.06 0.32 0.08l0.5 0.12l18.22 0.02c0.01 0.07 0.02 0.14 0.03 0.21c2.48 19.1 19.25 29.53 37.76 31.8c0 4.69 0 15.96 0 16.91h-0c-12.93 2.24 -24 9.94 -24 23.06h64c-0 -13.22 -11.07 -20.9 -24 -23.09h-0v-16.92c0.05 -0.01 0.1 -0.01 0.14 -0.02c18.93 -2.45 35.9 -13.31 37.45 -32.03c0.01 -0.08 3.5 -0.1 7.48 -0.1c5.28 0 11.42 0.04 11.42 0.04c0.11 -0.03 0.21 -0.05 0.32 -0.08c5.84 -1.6 15.05 -7.88 15.05 -15.54l0.13 0.75c0 0 0 -63.25 0 -72c0 -0.65 0 -1 0 -1l-32.5 0.13c-0.11 0.03 -0.21 0.05 -0.32 0.08c-0.12 0.03 -0.25 0.07 -0.37 0.11c-5.85 1.76 -14.68 7.93 -14.68 15.43h-64.25c0 -7.66 -9.21 -13.94 -15.05 -15.54c-0.11 -0.03 -0.22 -0.06 -0.32 -0.08l-32.5 -0.13z" />
+</vector>
diff --git a/app/src/main/res/drawable-v21/mnenomic_numpad_button.xml b/app/src/main/res/drawable-v21/mnenomic_numpad_button.xml
new file mode 100644
index 0000000..af4c22e
--- /dev/null
+++ b/app/src/main/res/drawable-v21/mnenomic_numpad_button.xml
@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+    <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle">
+        <gradient android:endColor="?attr/activeButtonColor" android:startColor="?attr/activeButtonColor" />
+        <corners android:radius="6dp" />
+    </shape>
diff --git a/app/src/main/res/drawable-v21/numpad_highlighted.xml b/app/src/main/res/drawable-v21/numpad_highlighted.xml
new file mode 100644
index 0000000..2c00338
--- /dev/null
+++ b/app/src/main/res/drawable-v21/numpad_highlighted.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <gradient
+        android:endColor="?attr/activeButtonColor"
+        android:startColor="?attr/activeButtonColor" />
+    <corners android:radius="6dp" />
+    <stroke
+        android:width="10px"
+        android:color="?attr/colorPrimaryDark" />
+</shape>
\ No newline at end of file
diff --git a/app/src/main/res/drawable-v21/numpad_highlighted_four.xml b/app/src/main/res/drawable-v21/numpad_highlighted_four.xml
new file mode 100644
index 0000000..87ce8d9
--- /dev/null
+++ b/app/src/main/res/drawable-v21/numpad_highlighted_four.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <gradient
+        android:endColor="?attr/activeButtonColor"
+        android:startColor="?attr/activeButtonColor" />
+    <corners android:radius="6dp" />
+    <stroke
+        android:width="10px"
+        android:color="?attr/standardVectorGraphic" />
+</shape>
\ No newline at end of file
diff --git a/app/src/main/res/drawable-v21/numpad_highlighted_three.xml b/app/src/main/res/drawable-v21/numpad_highlighted_three.xml
new file mode 100644
index 0000000..05aa808
--- /dev/null
+++ b/app/src/main/res/drawable-v21/numpad_highlighted_three.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <gradient
+        android:endColor="?attr/activeButtonColor"
+        android:startColor="?attr/activeButtonColor" />
+    <corners android:radius="6dp" />
+    <stroke
+        android:width="10px"
+        android:color="?attr/highlightedButtonBorder" />
+</shape>
\ No newline at end of file
diff --git a/app/src/main/res/drawable-xhdpi/ic_star_accent_48dp.png b/app/src/main/res/drawable-xhdpi/ic_star_accent_48dp.png
new file mode 100644
index 0000000..d8bbfa1
Binary files /dev/null and b/app/src/main/res/drawable-xhdpi/ic_star_accent_48dp.png differ
diff --git a/app/src/main/res/drawable-xhdpi/ic_star_grey_48dp.png b/app/src/main/res/drawable-xhdpi/ic_star_grey_48dp.png
new file mode 100644
index 0000000..55661b2
Binary files /dev/null and b/app/src/main/res/drawable-xhdpi/ic_star_grey_48dp.png differ
diff --git a/app/src/main/res/drawable/button_inactive.xml b/app/src/main/res/drawable/button_inactive.xml
new file mode 100644
index 0000000..523ab80
--- /dev/null
+++ b/app/src/main/res/drawable/button_inactive.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<selector xmlns:android="http://schemas.android.com/apk/res/android" >
+<!-- default -->
+<item>
+    <shape >
+        <solid
+            android:color="@color/middlegrey" />
+        <corners android:radius="6dp" />
+    </shape>
+</item>
+</selector>
\ No newline at end of file
diff --git a/app/src/main/res/drawable/button_standalone.xml b/app/src/main/res/drawable/button_standalone.xml
new file mode 100644
index 0000000..8f125d3
--- /dev/null
+++ b/app/src/main/res/drawable/button_standalone.xml
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<selector xmlns:android="http://schemas.android.com/apk/res/android" >
+    <!-- default -->
+    <item>
+        <shape >
+            <solid
+                android:color="@color/colorPrimary" />
+            <corners android:radius="6dp" />
+        </shape>
+    </item>
+</selector>
diff --git a/app/src/main/res/drawable/ic_star_grey_36dp.xml b/app/src/main/res/drawable/ic_star_grey_36dp.xml
deleted file mode 100644
index 456adf1..0000000
--- a/app/src/main/res/drawable/ic_star_grey_36dp.xml
+++ /dev/null
@@ -1,10 +0,0 @@
-<vector xmlns:android="http://schemas.android.com/apk/res/android"
-    android:width="54dp"
-    android:height="54dp"
-    android:viewportWidth="54"
-    android:viewportHeight="54">
-    <path
-        android:fillColor="?attr/rankingStarNotSelected"
-        android:name="Color Fill 1"
-        android:pathData="m27 39 13 7 -3 -15 11 -10 -15 -1 -6 -13 -6 13 -15 1 11 10 -3 15 13 -7z" />
-</vector>
diff --git a/app/src/main/res/drawable/ic_trophy_award_black_48dp.png b/app/src/main/res/drawable/ic_trophy_award_black_48dp.png
new file mode 100644
index 0000000..e85ed53
Binary files /dev/null and b/app/src/main/res/drawable/ic_trophy_award_black_48dp.png differ
diff --git a/app/src/main/res/drawable/ic_trophy_black_48dp.png b/app/src/main/res/drawable/ic_trophy_black_48dp.png
new file mode 100644
index 0000000..7d1620f
Binary files /dev/null and b/app/src/main/res/drawable/ic_trophy_black_48dp.png differ
diff --git a/app/src/main/res/drawable/mnenomic_numpad_button.xml b/app/src/main/res/drawable/mnenomic_numpad_button.xml
index af4c22e..12c4d14 100644
--- a/app/src/main/res/drawable/mnenomic_numpad_button.xml
+++ b/app/src/main/res/drawable/mnenomic_numpad_button.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
     <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="rectangle">
-        <gradient android:endColor="?attr/activeButtonColor" android:startColor="?attr/activeButtonColor" />
+        <gradient android:endColor="@color/lightblue" android:startColor="@color/lightblue" />
         <corners android:radius="6dp" />
     </shape>
diff --git a/app/src/main/res/drawable/numpad_highlighted.xml b/app/src/main/res/drawable/numpad_highlighted.xml
index 2c00338..7af2c1a 100644
--- a/app/src/main/res/drawable/numpad_highlighted.xml
+++ b/app/src/main/res/drawable/numpad_highlighted.xml
@@ -2,10 +2,10 @@
 <shape xmlns:android="http://schemas.android.com/apk/res/android"
     android:shape="rectangle">
     <gradient
-        android:endColor="?attr/activeButtonColor"
-        android:startColor="?attr/activeButtonColor" />
+        android:endColor="@color/lightblue"
+        android:startColor="@color/lightblue" />
     <corners android:radius="6dp" />
     <stroke
         android:width="10px"
-        android:color="?attr/colorPrimaryDark" />
+        android:color="@color/colorPrimaryDark" />
 </shape>
\ No newline at end of file
diff --git a/app/src/main/res/drawable/numpad_highlighted_four.xml b/app/src/main/res/drawable/numpad_highlighted_four.xml
index 87ce8d9..8b8e766 100644
--- a/app/src/main/res/drawable/numpad_highlighted_four.xml
+++ b/app/src/main/res/drawable/numpad_highlighted_four.xml
@@ -2,10 +2,10 @@
 <shape xmlns:android="http://schemas.android.com/apk/res/android"
     android:shape="rectangle">
     <gradient
-        android:endColor="?attr/activeButtonColor"
-        android:startColor="?attr/activeButtonColor" />
+        android:endColor="@color/lightblue"
+        android:startColor="@color/lightblue" />
     <corners android:radius="6dp" />
     <stroke
         android:width="10px"
-        android:color="?attr/standardVectorGraphic" />
+        android:color="@color/black" />
 </shape>
\ No newline at end of file
diff --git a/app/src/main/res/drawable/numpad_highlighted_three.xml b/app/src/main/res/drawable/numpad_highlighted_three.xml
index 05aa808..fe0f0cf 100644
--- a/app/src/main/res/drawable/numpad_highlighted_three.xml
+++ b/app/src/main/res/drawable/numpad_highlighted_three.xml
@@ -2,10 +2,10 @@
 <shape xmlns:android="http://schemas.android.com/apk/res/android"
     android:shape="rectangle">
     <gradient
-        android:endColor="?attr/activeButtonColor"
-        android:startColor="?attr/activeButtonColor" />
+        android:endColor="@color/lightblue"
+        android:startColor="@color/lightblue" />
     <corners android:radius="6dp" />
     <stroke
         android:width="10px"
-        android:color="?attr/highlightedButtonBorder" />
+        android:color="@color/yellow" />
 </shape>
\ No newline at end of file
diff --git a/app/src/main/res/drawable/ratingbar.xml b/app/src/main/res/drawable/ratingbar.xml
index b634ced..a461706 100644
--- a/app/src/main/res/drawable/ratingbar.xml
+++ b/app/src/main/res/drawable/ratingbar.xml
@@ -1,27 +1,12 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- Copyright (C) 2011 The Android Open Source Project
-
-     Licensed under the Apache License, Version 2.0 (the "License");
-     you may not use this file except in compliance with the License.
-     You may obtain a copy of the License at
-
-          http://www.apache.org/licenses/LICENSE-2.0
-
-     Unless required by applicable law or agreed to in writing, software
-     distributed under the License is distributed on an "AS IS" BASIS,
-     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-     See the License for the specific language governing permissions and
-     limitations under the License.
--->
-
 <layer-list xmlns:android="http://schemas.android.com/apk/res/android">
-    <item android:id="@android:id/background">
-        <bitmap
-            android:src="@drawable/ic_star_grey_36dp" />
-    </item>
-    <item android:id="@android:id/progress">
-        <bitmap
-            android:src="@drawable/ic_star_blue_36dp" />
-    </item>
-</layer-list>
-
+    <item
+        android:id="@android:id/background"
+        android:drawable="@drawable/ic_star_grey_48dp" />
+    <item
+        android:id="@android:id/secondaryProgress"
+        android:drawable="@drawable/ic_star_half_black_48dp" />
+    <item
+        android:id="@android:id/progress"
+        android:drawable="@drawable/ic_star_accent_48dp" />
+</layer-list>
\ No newline at end of file
diff --git a/app/src/main/res/layout-land/activity_about.xml b/app/src/main/res/layout-land/activity_about.xml
index b36a20c..818a033 100644
--- a/app/src/main/res/layout-land/activity_about.xml
+++ b/app/src/main/res/layout-land/activity_about.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
@@ -116,7 +117,7 @@
             android:adjustViewBounds="true"
             android:paddingEnd="50dp"
             android:paddingStart="50dp"
-            android:src="@drawable/secuso_logo_blau_blau" />
+            app:srcCompat="@drawable/secuso_logo_blau_blau" />
 
         <TextView
             android:layout_width="wrap_content"
diff --git a/app/src/main/res/layout-land/activity_daily_sudoku.xml b/app/src/main/res/layout-land/activity_daily_sudoku.xml
index bfd640c..3234646 100644
--- a/app/src/main/res/layout-land/activity_daily_sudoku.xml
+++ b/app/src/main/res/layout-land/activity_daily_sudoku.xml
@@ -108,7 +108,7 @@
                 android:layout_marginStart="16dp"
                 android:layout_marginLeft="16dp"
                 android:adjustViewBounds="true"
-                android:src="@drawable/icon_default_9x9"
+                app:srcCompat="@drawable/icon_default_9x9"
                 app:layout_constraintBottom_toBottomOf="parent"
                 app:layout_constraintEnd_toStartOf="@id/view"
                 app:layout_constraintHorizontal_bias="0.0"
diff --git a/app/src/main/res/layout-land/activity_main_menu.xml b/app/src/main/res/layout-land/activity_main_menu.xml
index 5389f69..96f4df7 100644
--- a/app/src/main/res/layout-land/activity_main_menu.xml
+++ b/app/src/main/res/layout-land/activity_main_menu.xml
@@ -108,7 +108,7 @@
                     android:layout_height="wrap_content"
                     android:gravity="center_vertical">
 
-                    <CheckBox
+                    <androidx.appcompat.widget.AppCompatCheckBox
                         android:id="@+id/circleButton"
                         style="@style/CheckBox"
                         android:layout_width="wrap_content"
@@ -157,7 +157,7 @@
                     android:capitalize="none"
                     android:clickable="false"
                     android:elevation="10dp"
-                    android:background="@drawable/standalone_button"/>
+                    android:background="@drawable/button_standalone"/>
 
                 <Button
                     android:textColor="?attr/lightestFontColor"
@@ -174,7 +174,7 @@
                     android:onClick="onClick"
                     android:capitalize="none"
                     android:clickable="true"
-                    android:background="@drawable/standalone_button"/>
+                    android:background="@drawable/button_standalone"/>
 
         </LinearLayout>
 
diff --git a/app/src/main/res/layout-land/fragment_stats.xml b/app/src/main/res/layout-land/fragment_stats.xml
index 409b7a6..44a4a4d 100644
--- a/app/src/main/res/layout-land/fragment_stats.xml
+++ b/app/src/main/res/layout-land/fragment_stats.xml
@@ -1,4 +1,5 @@
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:paddingLeft="@dimen/activity_horizontal_margin"
@@ -6,8 +7,7 @@
     android:paddingTop="@dimen/activity_vertical_margin"
     android:paddingBottom="@dimen/activity_vertical_margin"
     android:weightSum="5"
-    android:orientation="vertical"
-    tools:context="tu_darmstadt.sudoku.ui.StatsActivity$PlaceholderFragment">
+    android:orientation="vertical">
 
     <LinearLayout
         android:layout_width="fill_parent"
@@ -103,7 +103,7 @@
             android:layout_height="fill_parent"
             android:layout_gravity="center"
             android:id="@+id/statistic_image"
-            android:src="@drawable/icon_default_9x9"
+            app:srcCompat="@drawable/icon_default_9x9"
             android:adjustViewBounds="true"/>
         <RelativeLayout
             android:layout_width="0dp"
diff --git a/app/src/main/res/layout-small/activity_main_menu.xml b/app/src/main/res/layout-small/activity_main_menu.xml
deleted file mode 100644
index 4e1a425..0000000
--- a/app/src/main/res/layout-small/activity_main_menu.xml
+++ /dev/null
@@ -1,272 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<androidx.drawerlayout.widget.DrawerLayout android:id="@+id/drawer_layout_main"
-    android:layout_height="match_parent"
-    android:layout_width="match_parent"
-    android:fitsSystemWindows="true"
-    tools:openDrawer="start"
-    xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
-    xmlns:app="http://schemas.android.com/apk/res-auto">
-
-<androidx.coordinatorlayout.widget.CoordinatorLayout
-    xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
-    xmlns:app="http://schemas.android.com/apk/res-auto"
-    android:fitsSystemWindows="true"
-    tools:context="tu_darmstadt.sudoku.ui.MainActivity"
-    android:layout_height="match_parent"
-    android:layout_width="match_parent">
-
-    <com.google.android.material.appbar.AppBarLayout
-        android:id="@+id/appbar"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:theme="@style/AppTheme.AppBarOverlay">
-
-        <androidx.appcompat.widget.Toolbar
-             android:id="@+id/toolbar"
-             android:layout_width="match_parent"
-             android:layout_height="?attr/actionBarSize"
-             android:background="?attr/colorPrimary"
-             app:popupTheme="@style/AppTheme.PopupOverlay">
-
-        </androidx.appcompat.widget.Toolbar>
-
-
-    </com.google.android.material.appbar.AppBarLayout>
-
-   <LinearLayout
-        android:layout_height="match_parent"
-        android:layout_width="match_parent"
-        android:orientation="vertical"
-        android:weightSum="10"
-       android:id="@+id/main_content"
-        style="?android:buttonBarStyle"
-        app:layout_behavior="@string/appbar_scrolling_view_behavior">
-        <RelativeLayout
-            android:layout_width="fill_parent"
-            android:layout_height="0dp"
-            android:layoutDirection="ltr"
-            android:layout_weight="4">
-
-        <androidx.viewpager.widget.ViewPager
-            android:id="@+id/scroller"
-
-            android:layout_width="match_parent"
-            android:layout_height="match_parent"
-            app:layout_behavior="@string/appbar_scrolling_view_behavior" />
-
-            <ImageView
-                android:id="@+id/arrow_left"
-                android:layout_width="wrap_content"
-                android:layout_height="wrap_content"
-                app:srcCompat="@drawable/ic_keyboard_arrow_left_black_24dp"
-                android:layout_alignParentLeft="true"
-                android:layout_alignParentStart="true"
-                android:padding="@dimen/activity_horizontal_margin"
-                android:layout_marginStart="@dimen/activity_horizontal_margin"
-                android:layout_marginLeft="@dimen/activity_horizontal_margin"
-                android:layout_centerVertical="true"
-                android:onClick="onClick"/>
-            <ImageView
-                android:id="@+id/arrow_right"
-                android:layout_width="wrap_content"
-                android:layout_height="wrap_content"
-                app:srcCompat="@drawable/ic_keyboard_arrow_right_black_24dp"
-                android:layout_alignParentRight="true"
-                android:layout_alignParentEnd="true"
-                android:padding="@dimen/activity_horizontal_margin"
-                android:layout_marginEnd="@dimen/activity_horizontal_margin"
-                android:layout_marginRight="@dimen/activity_horizontal_margin"
-                android:layout_centerVertical="true"
-                android:onClick="onClick"/>
-        </RelativeLayout>
-        <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
-            xmlns:tools="http://schemas.android.com/tools"
-            android:layout_width="match_parent"
-            android:layout_height="0px"
-            android:layout_weight="6"
-            android:paddingLeft="@dimen/activity_horizontal_margin"
-            android:paddingRight="@dimen/activity_horizontal_margin"
-            android:paddingTop="@dimen/activity_vertical_margin"
-            android:paddingBottom="@dimen/activity_vertical_margin"
-            tools:context="tu_darmstadt.sudoku.ui.MainActivity"
-            android:orientation="vertical"
-            android:weightSum="8"
-            android:divider="#000"
-            android:baselineAligned="false"
-            android:gravity="center_horizontal">
-
-            <TextView
-                android:id="@+id/difficultyText"
-                android:layout_height="wrap_content"
-                android:layout_width="wrap_content"
-                android:text="@string/difficulty_easy"
-                android:textSize="@dimen/main_text_difficulty"/>
-
-            <androidx.constraintlayout.widget.ConstraintLayout
-                android:id="@+id/linearLayout3"
-                android:layout_width="wrap_content"
-                android:layout_height="wrap_content"
-                android:gravity="center_vertical">
-
-                <CheckBox
-                    android:id="@+id/circleButton"
-                    android:layout_width="wrap_content"
-                    android:layout_height="wrap_content"
-                    android:layout_marginEnd="3dp"
-                    android:layout_marginRight="3dp"
-                    android:button="@drawable/create_game_src"
-                    android:scaleX="0.75"
-                    android:scaleY="0.75"
-                    app:layout_constraintBottom_toBottomOf="@+id/difficultyBar"
-                    app:layout_constraintEnd_toStartOf="@+id/difficultyBar"
-                    app:layout_constraintStart_toStartOf="parent"
-                    app:layout_constraintTop_toTopOf="@+id/difficultyBar" />
-
-                <RatingBar
-                    android:id="@+id/difficultyBar"
-                    style="@style/RatingBar"
-                    android:layout_width="wrap_content"
-                    android:layout_height="wrap_content"
-                    android:layout_marginStart="32dp"
-                    android:layout_marginLeft="32dp"
-                    android:clickable="true"
-                    android:numStars="3"
-                    android:rating="1"
-                    android:scaleX="0.75"
-                    android:scaleY="0.75"
-                    android:stepSize="1"
-                    app:layout_constraintBottom_toBottomOf="parent"
-                    app:layout_constraintEnd_toEndOf="parent"
-                    app:layout_constraintStart_toStartOf="parent"
-                    app:layout_constraintTop_toTopOf="parent" />
-            </androidx.constraintlayout.widget.ConstraintLayout>
-
-            <Button
-                android:textColor="?attr/lightestFontColor"
-                android:layout_width="match_parent"
-                android:layout_height="0dp"
-                android:layout_marginLeft="@dimen/main_button_padding"
-                android:layout_marginRight="@dimen/main_button_padding"
-                android:text="@string/new_game"
-                android:textStyle="normal"
-                android:textSize="@dimen/text_size"
-                android:id="@+id/playButton"
-                android:layout_gravity="center_horizontal"
-                android:layout_weight="3"
-                android:onClick="onClick"
-                android:capitalize="none"
-                android:clickable="false"
-                android:elevation="10dp"
-                android:background="@drawable/standalone_button"/>
-
-            <Button
-                android:textColor="?attr/lightestFontColor"
-                android:layout_marginTop="20dp"
-                android:layout_width="match_parent"
-                android:layout_height="0dp"
-                android:layout_marginLeft="@dimen/main_button_padding"
-                android:layout_marginRight="@dimen/main_button_padding"
-                android:text="@string/menu_continue_game"
-                android:textStyle="normal"
-                android:textSize="@dimen/text_size"
-                android:id="@+id/continueButton"
-                android:layout_gravity="center_horizontal"
-                android:layout_weight="3"
-                android:onClick="onClick"
-                android:capitalize="none"
-                android:clickable="false"
-                android:background="@drawable/standalone_button"/>
-
-            <Button
-                android:layout_width="wrap_content"
-                android:layout_height="wrap_content"
-                android:text="Win Debug"
-                android:visibility="invisible"
-                android:onClick="callFragment"/>
-<!--
-            <LinearLayout
-                android:layout_width="match_parent"
-                android:layout_height="0dp"
-                android:layout_weight="2"
-                android:weightSum="2">
-                <Button
-                    android:layout_width="0dp"
-                    android:layout_height="match_parent"
-                    android:layout_marginLeft="30dp"
-                    android:layout_marginRight="1dp"
-                    android:text="@string/menu_highscore"
-                    android:textStyle="normal"
-                    android:id="@+id/highscoreButton"
-                    android:layout_gravity="center_horizontal"
-                    android:layout_weight="1"
-                    android:onClick="onClick"
-                    android:capitalize="none"
-                    android:clickable="false"/>
-                <Button
-                    android:layout_width="0dp"
-                    android:layout_height="match_parent"
-                    android:layout_marginLeft="1dp"
-                    android:layout_marginRight="30dp"
-                    android:text="@string/menu_settings"
-                    android:textStyle="normal"
-                    android:id="@+id/settingsButton"
-                    android:layout_gravity="center_horizontal"
-                    android:layout_weight="1"
-                    android:onClick="onClick"
-                    android:capitalize="none"
-                    android:clickable="false"/>
-            </LinearLayout>
-            <LinearLayout
-                android:layout_width="match_parent"
-                android:layout_height="0dp"
-                android:layout_weight="2"
-                android:weightSum="2">
-                <Button
-                    android:layout_width="0dp"
-                    android:layout_height="match_parent"
-                    android:layout_marginLeft="30dp"
-                    android:layout_marginRight="1dp"
-                    android:text="@string/menu_about"
-                    android:textStyle="normal"
-                    android:id="@+id/aboutButton"
-                    android:layout_gravity="center_horizontal"
-                    android:layout_weight="1"
-                    android:onClick="onClick"
-                    android:capitalize="none"
-                    android:clickable="false"/>
-                <Button
-                    android:layout_width="0dp"
-                    android:layout_height="match_parent"
-                    android:layout_marginLeft="1dp"
-                    android:layout_marginRight="30dp"
-                    android:text="@string/menu_help"
-                    android:textStyle="normal"
-                    android:id="@+id/helpButton"
-                    android:layout_gravity="center_horizontal"
-                    android:layout_weight="1"
-                    android:onClick="onClick"
-                    android:capitalize="none"
-                    android:clickable="false"/>
-            </LinearLayout>
--->
-        </LinearLayout>
-
-   </LinearLayout>
-
-</androidx.coordinatorlayout.widget.CoordinatorLayout>
-
-    <com.google.android.material.navigation.NavigationView
-        android:id="@+id/nav_view_main"
-        android:layout_width="wrap_content"
-        android:layout_height="match_parent"
-        android:layout_gravity="start"
-        android:fitsSystemWindows="true"
-        android:background="?attr/lightestBackGround"
-        app:itemTextColor="?attr/menuTextColor"
-        app:itemIconTint="?attr/menuTextColor"
-        app:menu="@menu/menu_drawer_main"
-        app:headerLayout="@layout/nav_header" />
-
-    </androidx.drawerlayout.widget.DrawerLayout>
\ No newline at end of file
diff --git a/app/src/main/res/layout-xlarge-land/activity_about.xml b/app/src/main/res/layout-xlarge-land/activity_about.xml
index 051389c..feaaca8 100644
--- a/app/src/main/res/layout-xlarge-land/activity_about.xml
+++ b/app/src/main/res/layout-xlarge-land/activity_about.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
@@ -116,7 +117,7 @@
             android:adjustViewBounds="true"
             android:paddingEnd="200dp"
             android:paddingStart="200dp"
-            android:src="@drawable/secuso_logo_blau_blau" />
+            app:srcCompat="@drawable/secuso_logo_blau_blau" />
 
         <TextView
             android:layout_width="wrap_content"
diff --git a/app/src/main/res/layout-xlarge-land/fragment_stats.xml b/app/src/main/res/layout-xlarge-land/fragment_stats.xml
index 6932511..a9c6471 100644
--- a/app/src/main/res/layout-xlarge-land/fragment_stats.xml
+++ b/app/src/main/res/layout-xlarge-land/fragment_stats.xml
@@ -1,12 +1,12 @@
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
     android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
     android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingTop="@dimen/activity_vertical_margin"
     android:paddingBottom="@dimen/activity_vertical_margin"
     android:weightSum="10"
-    android:orientation="vertical"
-    tools:context="tu_darmstadt.sudoku.ui.StatsActivity$PlaceholderFragment">
+    android:orientation="vertical">
 
     <LinearLayout
         android:layout_width="fill_parent"
@@ -19,7 +19,7 @@
             android:layout_height="fill_parent"
             android:layout_gravity="center"
             android:id="@+id/statistic_image"
-            android:src="@drawable/icon_default_9x9"
+            app:srcCompat="@drawable/icon_default_9x9"
             android:adjustViewBounds="true"/>
         <RelativeLayout
             android:layout_width="0dp"
diff --git a/app/src/main/res/layout-xlarge/activity_about.xml b/app/src/main/res/layout-xlarge/activity_about.xml
index c15dd32..93a8f00 100644
--- a/app/src/main/res/layout-xlarge/activity_about.xml
+++ b/app/src/main/res/layout-xlarge/activity_about.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
@@ -117,7 +118,7 @@
             android:layout_marginEnd="100dp"
             android:layout_marginStart="100dp"
             android:adjustViewBounds="true"
-            android:src="@drawable/secuso_logo_blau_blau" />
+            app:srcCompat="@drawable/secuso_logo_blau_blau" />
 
         <TextView
             android:layout_width="wrap_content"
diff --git a/app/src/main/res/layout-xlarge/activity_main_menu.xml b/app/src/main/res/layout-xlarge/activity_main_menu.xml
index 9d7e4d7..d431777 100644
--- a/app/src/main/res/layout-xlarge/activity_main_menu.xml
+++ b/app/src/main/res/layout-xlarge/activity_main_menu.xml
@@ -109,7 +109,7 @@
                 android:layout_height="wrap_content"
                 android:gravity="center_vertical">
 
-                <CheckBox
+                <androidx.appcompat.widget.AppCompatCheckBox
                     android:id="@+id/circleButton"
                     style="@style/CheckBox"
                     android:layout_width="wrap_content"
@@ -160,7 +160,7 @@
                 android:capitalize="none"
                 android:clickable="false"
                 android:elevation="10dp"
-                android:background="@drawable/standalone_button"/>
+                android:background="@drawable/button_standalone"/>
 
             <Button
                 android:textColor="?attr/lightestFontColor"
@@ -178,7 +178,7 @@
                 android:onClick="onClick"
                 android:capitalize="none"
                 android:clickable="false"
-                android:background="@drawable/standalone_button"/>
+                android:background="@drawable/button_standalone"/>
 <!--
             <LinearLayout
                 android:layout_width="match_parent"
diff --git a/app/src/main/res/layout-xlarge/fragment_stats.xml b/app/src/main/res/layout-xlarge/fragment_stats.xml
index b75bacb..5a287f5 100644
--- a/app/src/main/res/layout-xlarge/fragment_stats.xml
+++ b/app/src/main/res/layout-xlarge/fragment_stats.xml
@@ -1,12 +1,12 @@
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
     android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
     android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingTop="@dimen/activity_vertical_margin"
     android:paddingBottom="@dimen/activity_vertical_margin"
     android:weightSum="10"
-    android:orientation="vertical"
-    tools:context="tu_darmstadt.sudoku.ui.StatsActivity$PlaceholderFragment">
+    android:orientation="vertical">
 
     <LinearLayout
         android:layout_width="fill_parent"
@@ -19,7 +19,7 @@
             android:layout_height="fill_parent"
             android:layout_gravity="center"
             android:id="@+id/statistic_image"
-            android:src="@drawable/icon_default_9x9"
+            app:srcCompat="@drawable/icon_default_9x9"
             android:adjustViewBounds="true"/>
         <RelativeLayout
             android:layout_width="0dp"
diff --git a/app/src/main/res/layout-xlarge/win_screen_layout.xml b/app/src/main/res/layout-xlarge/win_screen_layout.xml
index 6e48fca..a199ef5 100644
--- a/app/src/main/res/layout-xlarge/win_screen_layout.xml
+++ b/app/src/main/res/layout-xlarge/win_screen_layout.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="fill_parent" android:layout_height="370dp"
     android:orientation="vertical"
     android:background="?attr/lightestBackGround"
@@ -25,7 +26,7 @@
                 android:layout_height="40dp"
                 android:layout_gravity="bottom"
                 android:background="?attr/backgroundSurroundingDialog"
-                android:src="@drawable/ic_trophy_award_black_48dp" />
+                app:srcCompat="@drawable/ic_trophy_award_black_48dp" />
             <View
                 android:layout_width="fill_parent"
                 android:layout_height="10dp"
@@ -124,7 +125,7 @@
                 android:layout_width="40dp"
                 android:layout_height="40dp"
                 android:layout_gravity="bottom"
-                android:src="@drawable/ic_trophy_award_black_48dp"
+                app:srcCompat="@drawable/ic_trophy_award_black_48dp"
                 android:background="?attr/backgroundSurroundingDialog" />
             <View
                 android:layout_width="fill_parent"
@@ -147,7 +148,7 @@
             android:id="@+id/win_continue_button"
             android:layout_width="0dp"
             android:layout_height="wrap_content"
-            android:background="@drawable/standalone_button"
+            android:background="@drawable/button_standalone"
             android:textColor="?attr/lightestFontColor"
             android:layout_weight="1"
             android:text="@string/win_button_text"
@@ -156,7 +157,7 @@
             android:id="@+id/win_showGame_button"
             android:layout_width="0dp"
             android:layout_height="wrap_content"
-            android:background="@drawable/standalone_button"
+            android:background="@drawable/button_standalone"
             android:textColor="?attr/lightestFontColor"
             android:layout_weight="1"
             android:text="@string/win_show_game"
diff --git a/app/src/main/res/layout/activity_about.xml b/app/src/main/res/layout/activity_about.xml
index 09bc047..8e39d6b 100644
--- a/app/src/main/res/layout/activity_about.xml
+++ b/app/src/main/res/layout/activity_about.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
@@ -113,7 +114,7 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:adjustViewBounds="true"
-            android:src="@drawable/secuso_logo_blau_blau" />
+            app:srcCompat="@drawable/secuso_logo_blau_blau" />
 
         <TextView
             android:layout_width="wrap_content"
diff --git a/app/src/main/res/layout/activity_daily_sudoku.xml b/app/src/main/res/layout/activity_daily_sudoku.xml
index 73322b0..0b677a7 100644
--- a/app/src/main/res/layout/activity_daily_sudoku.xml
+++ b/app/src/main/res/layout/activity_daily_sudoku.xml
@@ -11,8 +11,7 @@
     android:id="@+id/linearLayout10"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    android:fitsSystemWindows="true"
-    app:statusBarBackground="?attr/colorPrimary">
+    android:fitsSystemWindows="true">
 
     <View
         android:id="@+id/view3"
@@ -54,7 +53,7 @@
             android:layout_marginEnd="16dp"
             android:layout_marginRight="16dp"
             android:adjustViewBounds="true"
-            android:src="@drawable/icon_default_9x9"
+            app:srcCompat="@drawable/icon_default_9x9"
             app:layout_constraintBottom_toBottomOf="parent"
             app:layout_constraintEnd_toStartOf="@id/view"
             app:layout_constraintHorizontal_bias="0.0"
@@ -68,7 +67,6 @@
             style="?android:attr/ratingBarStyleSmall"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-
             android:layout_marginEnd="8dp"
             android:layout_marginRight="8dp"
             android:numStars="4"
diff --git a/app/src/main/res/layout/activity_main_menu.xml b/app/src/main/res/layout/activity_main_menu.xml
index d9d2314..e0efd48 100644
--- a/app/src/main/res/layout/activity_main_menu.xml
+++ b/app/src/main/res/layout/activity_main_menu.xml
@@ -108,7 +108,7 @@
                     android:orientation="horizontal"
                     android:id="@+id/linearLayout4">
 
-                    <CheckBox
+                    <androidx.appcompat.widget.AppCompatCheckBox
                         android:id="@+id/circleButton"
                         android:layout_width="wrap_content"
                         android:layout_height="wrap_content"
@@ -130,8 +130,8 @@
                         android:layout_marginStart="41dp"
                         android:layout_marginLeft="41dp"
                         android:clickable="true"
-                        android:numStars="3"
-                        android:rating="0.5"
+                        android:numStars="4"
+                        android:rating="2"
                         android:stepSize="1"
                         app:layout_constraintBottom_toBottomOf="parent"
                         app:layout_constraintEnd_toEndOf="parent"
@@ -154,7 +154,7 @@
                     android:onClick="onClick"
                     android:clickable="false"
                     android:elevation="10dp"
-                    android:background="@drawable/standalone_button"/>
+                    android:background="@drawable/button_standalone"/>
 
                 <Button
                     android:textColor="?attr/lightestFontColor"
@@ -172,7 +172,7 @@
                     android:onClick="onClick"
                     android:capitalize="none"
                     android:clickable="false"
-                    android:background="@drawable/standalone_button"/>
+                    android:background="@drawable/button_standalone"/>
 
                 <!--  <Button
                       android:layout_width="wrap_content"
@@ -257,11 +257,12 @@
         android:layout_width="wrap_content"
         android:layout_height="match_parent"
         android:layout_gravity="start"
-        android:fitsSystemWindows="true"
         android:background="?attr/lightestBackGround"
-        app:itemTextColor="?attr/menuTextColor"
+        android:fitsSystemWindows="true"
+        app:headerLayout="@layout/nav_header"
         app:itemIconTint="?attr/menuTextColor"
+        app:itemTextColor="?attr/menuTextColor"
         app:menu="@menu/menu_drawer_main"
-        app:headerLayout="@layout/nav_header" />
+        tools:visibility="gone" />
 
 </androidx.drawerlayout.widget.DrawerLayout>
diff --git a/app/src/main/res/layout/activity_tutorial.xml b/app/src/main/res/layout/activity_tutorial.xml
index 7f3fe90..e2439f2 100644
--- a/app/src/main/res/layout/activity_tutorial.xml
+++ b/app/src/main/res/layout/activity_tutorial.xml
@@ -6,7 +6,6 @@
     android:layout_height="match_parent"
     tools:showIn="@layout/activity_tutorial">
 
-
     <androidx.viewpager.widget.ViewPager
         android:id="@+id/view_pager"
         android:layout_width="match_parent"
diff --git a/app/src/main/res/layout/fragment_main_menu.xml b/app/src/main/res/layout/fragment_main_menu.xml
index 0cf37fa..2d46bb0 100644
--- a/app/src/main/res/layout/fragment_main_menu.xml
+++ b/app/src/main/res/layout/fragment_main_menu.xml
@@ -1,4 +1,5 @@
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
@@ -8,8 +9,7 @@
     android:paddingBottom="@dimen/activity_vertical_margin"
     android:gravity="center_horizontal|center_vertical"
     android:orientation="vertical"
-    android:weightSum="8"
-    tools:context="tu_darmstadt.sudoku.ui.MainActivity$GameTypeFragment">
+    android:weightSum="8">
 
     <TextView android:id="@+id/section_label"
         android:text="Label"
@@ -25,7 +25,7 @@
         android:layout_width="wrap_content"
         android:adjustViewBounds="true"
         android:layout_centerInParent="true"
-        android:src="@drawable/icon_default_9x9"
+        app:srcCompat="@drawable/icon_default_9x9"
         android:layout_height="0dp" />
 
 </LinearLayout>
diff --git a/app/src/main/res/layout/fragment_stats.xml b/app/src/main/res/layout/fragment_stats.xml
index efea7f0..73df622 100644
--- a/app/src/main/res/layout/fragment_stats.xml
+++ b/app/src/main/res/layout/fragment_stats.xml
@@ -1,4 +1,5 @@
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
     android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
     android:paddingRight="@dimen/activity_horizontal_margin"
@@ -19,7 +20,7 @@
             android:layout_height="fill_parent"
             android:layout_gravity="center"
             android:id="@+id/statistic_image"
-            android:src="@drawable/icon_default_9x9"
+            app:srcCompat="@drawable/icon_default_9x9"
             android:adjustViewBounds="true"/>
         <RelativeLayout
             android:layout_width="0dp"
diff --git a/app/src/main/res/layout/tutorial_slide1.xml b/app/src/main/res/layout/tutorial_slide1.xml
index 880eea7..2c14780 100644
--- a/app/src/main/res/layout/tutorial_slide1.xml
+++ b/app/src/main/res/layout/tutorial_slide1.xml
@@ -3,7 +3,6 @@
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:background="?attr/backgroundTutorialSlide">
-
     <LinearLayout
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
@@ -11,8 +10,6 @@
         android:gravity="center_horizontal"
         android:layout_centerVertical="true"
         android:orientation="vertical">
-
-
         <TextView
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
@@ -20,14 +17,11 @@
             android:textColor="?attr/lightestFontColor"
             android:textSize="@dimen/slide_title"
             android:textStyle="bold" />
-
         <ImageView
             android:layout_marginTop="25dp"
             android:layout_width="@dimen/img_width_height"
             android:layout_height="@dimen/img_width_height"
-            android:background="@drawable/splash_icon"
-            />
-
+            android:background="@drawable/splash_icon"/>
         <TextView
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
@@ -39,6 +33,5 @@
             android:gravity="center"
             android:textColor="?attr/lightestFontColor"
             android:textSize="@dimen/slide_desc" />
-
     </LinearLayout>
 </RelativeLayout>
\ No newline at end of file
diff --git a/app/src/main/res/layout/tutorial_slide2.xml b/app/src/main/res/layout/tutorial_slide2.xml
index b8343b4..761159d 100644
--- a/app/src/main/res/layout/tutorial_slide2.xml
+++ b/app/src/main/res/layout/tutorial_slide2.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:background="?attr/backgroundTutorialSlide">
@@ -30,18 +31,18 @@
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:layout_gravity="center"
-                android:src="@drawable/ic_keyboard_arrow_left_black_24dp"/>
+                app:srcCompat="@drawable/ic_keyboard_arrow_left_black_24dp"/>
             <ImageView
                 android:layout_width="100dp"
                 android:layout_height="100dp"
                 android:adjustViewBounds="true"
                 android:layout_gravity="center"
-                android:src="@drawable/icon_default_9x9"/>
+                app:srcCompat="@drawable/icon_default_9x9"/>
             <ImageView
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:layout_gravity="center"
-                android:src="@drawable/ic_keyboard_arrow_right_black_24dp"/>
+                app:srcCompat="@drawable/ic_keyboard_arrow_right_black_24dp"/>
         </LinearLayout>
 
         <TextView
diff --git a/app/src/main/res/layout/win_screen_layout.xml b/app/src/main/res/layout/win_screen_layout.xml
index 3733346..a64279a 100644
--- a/app/src/main/res/layout/win_screen_layout.xml
+++ b/app/src/main/res/layout/win_screen_layout.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="fill_parent" android:layout_height="320dp"
     android:orientation="vertical"
     android:background="?attr/lightestBackGround"
@@ -26,7 +27,7 @@
                 android:layout_height="40dp"
                 android:layout_gravity="bottom"
                 android:background="?attr/backgroundSurroundingDialog"
-                android:src="@drawable/ic_trophy_award_black_48dp" />
+                app:srcCompat="@drawable/ic_trophy_award_black_48dp" />
             <View
                 android:layout_width="fill_parent"
                 android:layout_height="10dp"
@@ -127,7 +128,7 @@
                 android:layout_width="40dp"
                 android:layout_height="40dp"
                 android:layout_gravity="bottom"
-                android:src="@drawable/ic_trophy_award_black_48dp"
+                app:srcCompat="@drawable/ic_trophy_award_black_48dp"
                 android:background="?attr/backgroundSurroundingDialog" />
             <View
                 android:layout_width="fill_parent"
@@ -150,7 +151,7 @@
             android:id="@+id/win_continue_button"
             android:layout_width="0dp"
             android:layout_height="wrap_content"
-            android:background="@drawable/standalone_button"
+            android:background="@drawable/button_standalone"
             android:textColor="?attr/lightestFontColor"
             android:layout_weight="1"
             android:text="@string/win_button_text"
@@ -159,7 +160,7 @@
             android:id="@+id/win_showGame_button"
             android:layout_width="0dp"
             android:layout_height="wrap_content"
-            android:background="@drawable/standalone_button"
+            android:background="@drawable/button_standalone"
             android:textColor="?attr/lightestFontColor"
             android:layout_weight="1"
             android:text="@string/win_show_game"
diff --git a/build.gradle b/build.gradle
index db1fb47..a6ad490 100644
--- a/build.gradle
+++ b/build.gradle
@@ -6,7 +6,7 @@ buildscript {
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.6.2'
+        classpath 'com.android.tools.build:gradle:4.0.1'
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 44bb974..177ea3b 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
-#Wed Oct 23 12:21:08 CEST 2019
+#Tue Oct 06 10:50:26 CEST 2020
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.4-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.1.1-all.zip