diff --git a/.idea/vcs.xml b/.idea/vcs.xml
index 6564d52..94a25f7 100644
--- a/.idea/vcs.xml
+++ b/.idea/vcs.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="VcsDirectoryMappings">
-    <mapping directory="" vcs="" />
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
   </component>
 </project>
\ No newline at end of file
diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 2948c5e..c429233 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -8,15 +8,6 @@
         android:label="@string/app_name"
         android:supportsRtl="true"
         android:theme="@style/AppTheme" >
-        <!--<activity
-            android:name=".MainMenu"
-            android:label="@string/app_name"
-            android:theme="@style/AppTheme.NoActionBar" >
-            <intent-filter>
-                <action android:name="android.intent.action.MAIN" />
-                <category android:name="android.intent.category.LAUNCHER" />
-            </intent-filter>
-        </activity>-->
         <activity
             android:name=".GameView"
             android:label="@string/app_name"
diff --git a/app/src/main/java/tu_darmstadt/sudoku/controller/GameController.java b/app/src/main/java/tu_darmstadt/sudoku/controller/GameController.java
index 6658d6c..ae26be0 100644
--- a/app/src/main/java/tu_darmstadt/sudoku/controller/GameController.java
+++ b/app/src/main/java/tu_darmstadt/sudoku/controller/GameController.java
@@ -1,12 +1,15 @@
 package tu_darmstadt.sudoku.controller;
 
-import android.util.Log;
-
-import tu_darmstadt.sudoku.game.*;
-
 import java.util.LinkedList;
 import java.util.List;
-import java.util.ArrayList;
+
+import tu_darmstadt.sudoku.game.CellConflict;
+import tu_darmstadt.sudoku.game.CellConflictList;
+import tu_darmstadt.sudoku.game.GameCell;
+import tu_darmstadt.sudoku.game.GameField;
+import tu_darmstadt.sudoku.game.GameSettings;
+import tu_darmstadt.sudoku.game.GameType;
+import tu_darmstadt.sudoku.game.ICellAction;
 
 /**
  * Created by Chris on 06.11.2015.
@@ -17,8 +20,9 @@ public class GameController {
     private GameField gameField;
     private CellConflictList errorList = new CellConflictList();
     private GameSettings settings = new GameSettings();
+    private LinkedList<IModelChangeListener> listeners = new LinkedList<>();
 
-//    private SudokuSolver solver;
+//    private Default9x9Solver solver;
 //    private SudokuGenerator generator;
 
     public GameController() {
@@ -36,6 +40,8 @@ public class GameController {
         }
     }*/
 
+
+
     public void setValue(int row, int col, int value) {
         GameCell cell = gameField.getCell(row, col);
         if (!cell.isFixed() && isValidNumber(value)) {
@@ -47,13 +53,14 @@ public class GameController {
                 updateList.addAll(gameField.getRow(cell.getRow()));
                 updateList.addAll(gameField.getColumn(cell.getCol()));
                 updateList.addAll(gameField.getSection(cell.getRow(), cell.getCol()));
-                deleteNote(updateList, value);
+                deleteNotes(updateList, value);
             }
-
         }
     }
 
-    public void deleteNote(List<GameCell> updateList, int value) {
+
+
+    public void deleteNotes(List<GameCell> updateList, int value) {
         for(GameCell c : updateList) {
             c.deleteNote(value);
         }
@@ -125,6 +132,50 @@ public class GameController {
         return errorList;
     }
 
+    public void resetLevel() {
+        gameField.actionOnCells(new ICellAction<Boolean>() {
+            @Override
+            public Boolean action(GameCell gc, Boolean existing) {
+                gc.reset();
+                return true;
+            }
+        }, true);
+        notifyListeners();
+    }
+
+    public boolean deleteValue(int row, int col) {
+        GameCell c = gameField.getCell(row,col);
+        if(!c.isFixed()) {
+            c.setValue(0);
+            notifyListeners();
+            return true;
+        }
+        return false;
+    }
+
+    public void setNote(int row, int col, int value) {
+        GameCell c = gameField.getCell(row,col);
+        c.setNote(value);
+        notifyListeners();
+    }
+
+    public boolean[] getNotes(int row, int col) {
+        GameCell c = gameField.getCell(row,col);
+        return c.getNotes().clone();
+    }
+
+    public void deleteNote(int row, int col, int value) {
+        GameCell c = gameField.getCell(row,col);
+        c.deleteNote(value);
+        notifyListeners();
+    }
+
+    public void toggleNote(int row, int col, int value) {
+        GameCell c = gameField.getCell(row,col);
+        c.toggleNote(value);
+        notifyListeners();
+    }
+
     /** Debug only method
      *
      * @return the Field represented as a String
@@ -132,4 +183,17 @@ public class GameController {
     public String getFieldAsString() {
         return gameField.toString();
     }
+
+    public void registerListener(IModelChangeListener l) {
+        if(!listeners.contains(l)) {
+            listeners.add(l);
+        }
+    }
+
+    public void notifyListeners() {
+        for(IModelChangeListener l : listeners) {
+            l.onModelChanged();
+        }
+    }
+
 }
diff --git a/app/src/main/java/tu_darmstadt/sudoku/controller/IModelChangeListener.java b/app/src/main/java/tu_darmstadt/sudoku/controller/IModelChangeListener.java
new file mode 100644
index 0000000..f551e96
--- /dev/null
+++ b/app/src/main/java/tu_darmstadt/sudoku/controller/IModelChangeListener.java
@@ -0,0 +1,8 @@
+package tu_darmstadt.sudoku.controller;
+
+/**
+ * Created by Chris on 11.11.2015.
+ */
+public interface IModelChangeListener {
+    public void onModelChanged();
+}
diff --git a/app/src/main/java/tu_darmstadt/sudoku/game/GameCell.java b/app/src/main/java/tu_darmstadt/sudoku/game/GameCell.java
index 202bf8b..3593041 100644
--- a/app/src/main/java/tu_darmstadt/sudoku/game/GameCell.java
+++ b/app/src/main/java/tu_darmstadt/sudoku/game/GameCell.java
@@ -1,14 +1,17 @@
 package tu_darmstadt.sudoku.game;
 
+import java.util.Arrays;
+
 /**
  * Created by Chris on 06.11.2015.
  */
-public class GameCell {
+public class GameCell implements Cloneable {
 
     private int row = 0;
     private int col = 0;
     private int value = 0;
     private boolean fixed = false;
+    private int noteCount = 0;
     private boolean notes[];
     private int size = 0;
 
@@ -59,18 +62,28 @@ public class GameCell {
      * @param val the value to be toggled.
      */
     public void toggleNote(int val) {
-        if(!isFixed())
+        if(!isFixed()) {
+            noteCount = notes[val - 1] ? noteCount - 1 : noteCount + 1;
             notes[val - 1] = !notes[val - 1];
+        }
     }
 
     public void setNote(int val) {
-        if(!isFixed())
+        if(!isFixed()) {
+            noteCount = notes[val - 1] ? noteCount : noteCount + 1;
             notes[val - 1] = true;
+        }
     }
 
     public void deleteNote(int val) {
-        if(!isFixed())
+        if(!isFixed()) {
+            noteCount = notes[val - 1] ? noteCount - 1 : noteCount;
             notes[val - 1] = false;
+        }
+    }
+
+    public int getNoteCount() {
+        return noteCount;
     }
 
     public boolean[] getNotes() {
@@ -81,6 +94,7 @@ public class GameCell {
      * Clear the notes array (set everything to false).
      */
     public void deleteNotes() {
+        noteCount = 0;
         notes = new boolean[size];
     }
 
@@ -134,4 +148,19 @@ public class GameCell {
 
         return sb.toString();
     }
+
+    public Boolean reset() {
+        if(isFixed()) {
+            return false;
+        }
+        setValue(0);
+        return true;
+    }
+
+    @Override
+    public GameCell clone() throws CloneNotSupportedException {
+        GameCell clone = (GameCell) super.clone();
+        clone.notes = (notes == null) ? null : Arrays.copyOf(notes, notes.length);
+        return clone;
+    }
 }
diff --git a/app/src/main/java/tu_darmstadt/sudoku/game/GameField.java b/app/src/main/java/tu_darmstadt/sudoku/game/GameField.java
index bf3b09d..865f016 100644
--- a/app/src/main/java/tu_darmstadt/sudoku/game/GameField.java
+++ b/app/src/main/java/tu_darmstadt/sudoku/game/GameField.java
@@ -1,11 +1,12 @@
 package tu_darmstadt.sudoku.game;
 
+import java.util.Arrays;
 import java.util.LinkedList;
 
 /**
  * Created by Christopher Beckmann on 06.11.2015.
  */
-public class GameField {
+public class GameField implements Cloneable {
 
     //private int id;
     private int sectionHeight;
@@ -49,6 +50,9 @@ public class GameField {
                 break;
             case Unspecified:
             default:
+                this.size = 1;
+                this.sectionHeight = 1;
+                this.sectionWidth = 1;
                 throw new IllegalArgumentException("GameType can not be unspecified.");
         }
     }
@@ -90,19 +94,15 @@ public class GameField {
         return result;
     }
 
-    public LinkedList<GameCell> getSection(int sec) {
-        LinkedList<GameCell> result = new LinkedList<GameCell>();
-        for(int i = 0; i < size ; i++) {    // row
-            for(int j = 0 ; j < size ; j++) {   // col
-                if((int)(Math.floor(i/sectionHeight)*sectionHeight + Math.floor(j/sectionWidth)) == sec) {
-                    result.add(field[i][j]);
+    public LinkedList<GameCell> getSection(final int sec) {
+        return actionOnCells(new ICellAction<LinkedList<GameCell>>() {
+            @Override
+            public LinkedList<GameCell> action(GameCell gc, LinkedList<GameCell> existing) {
+                if((int)(Math.floor(gc.getRow()/sectionHeight)*sectionHeight + Math.floor(gc.getCol()/sectionWidth)) == sec) {
+                    existing.add(gc);
                 }
-                if(result.size() >= sectionHeight*sectionWidth) {
-                    break;
-                }
-            }
-        }
-        return result;
+                return existing;
+            }}, new LinkedList<GameCell>());
     }
 
     public LinkedList<GameCell> getSection(int row, int col) {
@@ -114,16 +114,40 @@ public class GameField {
         return size;
     }
 
+    public <T> T actionOnCells(ICellAction<T> ca, T existing) {
+        for(int i = 0; i < field.length; i++) {
+            for(int j = 0; j < field[i].length; j++) {
+                existing = ca.action(field[i][j], existing);
+            }
+        }
+        return existing;
+    }
+
+    @Override
+    public GameField clone() throws CloneNotSupportedException {
+        GameField clone = (GameField) super.clone();
+
+        GameCell[][] cloneField = new GameCell[size][size];
+        for(int i = 0; i < size; i++) {
+            for(int j = 0; j < size; j++) {
+                cloneField[i][j] = field[i][j].clone();
+            }
+        }
+        clone.field = cloneField;
+
+        return clone;
+    }
+
     @Override
     public String toString() {
         StringBuilder sb = new StringBuilder();
 
-        sb.append("GameField: "); sb.append("\n");
+        sb.append("[GameField: \n");
 
-        for(int i = 0; i < size; i++) {
+        for (int i = 0; i < size; i++) {
 
-            for(int j = 0; j < size; j++) {
-                if(j % sectionWidth == 0) {
+            for (int j = 0; j < size; j++) {
+                if (j % sectionWidth == 0) {
                     sb.append("\t");
                 }
 
@@ -131,7 +155,7 @@ public class GameField {
                 sb.append(" ");
             }
 
-            sb.append("\n");
+            sb.append("]");
         }
         return sb.toString();
     }
diff --git a/app/src/main/java/tu_darmstadt/sudoku/game/ICellAction.java b/app/src/main/java/tu_darmstadt/sudoku/game/ICellAction.java
new file mode 100644
index 0000000..f2ee966
--- /dev/null
+++ b/app/src/main/java/tu_darmstadt/sudoku/game/ICellAction.java
@@ -0,0 +1,8 @@
+package tu_darmstadt.sudoku.game;
+
+/**
+ * Created by Chris on 10.11.2015.
+ */
+public interface ICellAction<T> {
+    T action(GameCell gc, T existing);
+}
diff --git a/app/src/main/java/tu_darmstadt/sudoku/game/solver/Default9x9Solver.java b/app/src/main/java/tu_darmstadt/sudoku/game/solver/Default9x9Solver.java
new file mode 100644
index 0000000..f6f77db
--- /dev/null
+++ b/app/src/main/java/tu_darmstadt/sudoku/game/solver/Default9x9Solver.java
@@ -0,0 +1,89 @@
+package tu_darmstadt.sudoku.game.solver;
+
+import tu_darmstadt.sudoku.game.GameCell;
+import tu_darmstadt.sudoku.game.GameField;
+import tu_darmstadt.sudoku.game.ICellAction;
+
+/**
+ * Created by Chris on 10.11.2015.
+ */
+public class Default9x9Solver implements ISolver {
+
+    private GameField gameField = null;
+
+    Default9x9Solver(GameField gameField) {
+        try {
+            if(gameField == null) {
+                throw new IllegalArgumentException("GameField may not be null.");
+            }
+
+            this.gameField = gameField.clone();
+        } catch(CloneNotSupportedException e) {
+            throw new IllegalArgumentException("This GameField is not cloneable.", e);
+        }
+    }
+
+    public boolean solve() {
+
+        checkSolvedCells();
+        /*
+        if(showPossibles()) return solve();
+
+        if(searchHiddenSingles()) return solve();
+
+        if(searchNakedPairsTriples()) return solve();
+
+        if(searchHiddenPairsTriples()) return solve();
+
+        if(searchNakedQuads()) return solve();
+
+        if(searchPointingPairs()) return solve();
+
+        if(searchBoxLineReduction()) return solve();
+
+        selectBestCell();
+        */
+
+
+
+
+
+
+        return true;
+    }
+
+    @Override
+    public boolean calculateNextPossibleStep() {
+        return false;
+    }
+
+    public GameField getGameField() {
+        return gameField;
+    }
+
+    private boolean checkSolvedCells() {
+        return gameField.actionOnCells(new ICellAction<Boolean>() {
+            @Override
+            public Boolean action(GameCell gc, Boolean existing) {
+                boolean oneNote = false;
+                int value = -1;
+                if(gc.getNoteCount() == 1) {
+                    for(int i = 0; i < gameField.getSize(); i++) {
+                        if(gc.getNotes()[i]) {
+                            value = i;
+                            break;
+                        }
+                    }
+                    gc.setValue(value);
+                    existing = true;
+                }
+                return existing;
+            }}, false);
+    }
+
+    private boolean searchHiddenSingles() {
+        return false;
+    }
+
+
+}
diff --git a/app/src/main/java/tu_darmstadt/sudoku/game/solver/ISolver.java b/app/src/main/java/tu_darmstadt/sudoku/game/solver/ISolver.java
new file mode 100644
index 0000000..5d12da9
--- /dev/null
+++ b/app/src/main/java/tu_darmstadt/sudoku/game/solver/ISolver.java
@@ -0,0 +1,16 @@
+package tu_darmstadt.sudoku.game.solver;
+
+import tu_darmstadt.sudoku.game.GameField;
+
+/**
+ * Created by Chris on 11.11.2015.
+ */
+public interface ISolver {
+
+    public boolean solve();
+
+    public boolean calculateNextPossibleStep();
+
+    public GameField getGameField();
+
+}
diff --git a/app/src/main/java/tu_darmstadt/sudoku/view/MainMenu.java b/app/src/main/java/tu_darmstadt/sudoku/view/MainMenu.java
deleted file mode 100644
index d016c10..0000000
--- a/app/src/main/java/tu_darmstadt/sudoku/view/MainMenu.java
+++ /dev/null
@@ -1,52 +0,0 @@
-package tu_darmstadt.sudoku.view;
-
-import android.os.Bundle;
-import android.support.design.widget.FloatingActionButton;
-import android.support.design.widget.Snackbar;
-import android.support.v7.app.AppCompatActivity;
-import android.support.v7.widget.Toolbar;
-import android.view.View;
-import android.view.Menu;
-import android.view.MenuItem;
-
-public class MainMenu extends AppCompatActivity {
-
-    @Override
-    protected void onCreate(Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-        setContentView(R.layout.activity_main_menu);
-        //Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
-        //setSupportActionBar(toolbar);
-
-        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
-        fab.setOnClickListener(new View.OnClickListener() {
-            @Override
-            public void onClick(View view) {
-                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
-                        .setAction("Action", null).show();
-            }
-        });
-    }
-
-    @Override
-    public boolean onCreateOptionsMenu(Menu menu) {
-        // Inflate the menu; this adds items to the action bar if it is present.
-        getMenuInflater().inflate(R.menu.menu_main_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.
-        int id = item.getItemId();
-
-        //noinspection SimplifiableIfStatement
-        if (id == R.id.action_settings) {
-            return true;
-        }
-
-        return super.onOptionsItemSelected(item);
-    }
-}
diff --git a/app/src/main/res/layout/activity_main_menu.xml b/app/src/main/res/layout/activity_main_menu.xml
deleted file mode 100644
index 7697f78..0000000
--- a/app/src/main/res/layout/activity_main_menu.xml
+++ /dev/null
@@ -1,20 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<android.support.design.widget.CoordinatorLayout
-    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:fitsSystemWindows="true" tools:context=".MainMenu">
-
-    <android.support.design.widget.AppBarLayout android:layout_height="wrap_content"
-        android:layout_width="match_parent" android:theme="@style/AppTheme.AppBarOverlay">
-
-    </android.support.design.widget.AppBarLayout>
-
-    <include layout="@layout/content_main_menu" />
-
-    <android.support.design.widget.FloatingActionButton android:id="@+id/fab"
-        android:layout_width="wrap_content" android:layout_height="wrap_content"
-        android:layout_gravity="bottom|end" android:layout_margin="@dimen/fab_margin"
-        android:src="@android:drawable/ic_dialog_email" />
-
-</android.support.design.widget.CoordinatorLayout>
diff --git a/app/src/main/res/layout/content_main_menu.xml b/app/src/main/res/layout/content_main_menu.xml
deleted file mode 100644
index 7f0cbd7..0000000
--- a/app/src/main/res/layout/content_main_menu.xml
+++ /dev/null
@@ -1,14 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<RelativeLayout 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: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"
-    app:layout_behavior="@string/appbar_scrolling_view_behavior"
-    tools:showIn="@layout/activity_main_menu" tools:context=".MainMenu">
-
-    <TextView android:text="Hello World! :)" android:layout_width="wrap_content"
-        android:layout_height="wrap_content" />
-</RelativeLayout>
diff --git a/app/src/main/res/menu/menu_main_menu.xml b/app/src/main/res/menu/menu_main_menu.xml
deleted file mode 100644
index 2b4455a..0000000
--- a/app/src/main/res/menu/menu_main_menu.xml
+++ /dev/null
@@ -1,6 +0,0 @@
-<menu 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" tools:context=".MainMenu">
-    <item android:id="@+id/action_settings" android:title="@string/action_settings"
-        android:orderInCategory="100" app:showAsAction="never" />
-</menu>
diff --git a/app/src/test/java/tu_darmstadt/sudoku/controller/GameControllerTest.java b/app/src/test/java/tu_darmstadt/sudoku/controller/GameControllerTest.java
index df32634..3d76f4a 100644
--- a/app/src/test/java/tu_darmstadt/sudoku/controller/GameControllerTest.java
+++ b/app/src/test/java/tu_darmstadt/sudoku/controller/GameControllerTest.java
@@ -1,11 +1,8 @@
 package tu_darmstadt.sudoku.controller;
 
 import org.junit.Before;
-import org.junit.BeforeClass;
 import org.junit.Test;
 
-import tu_darmstadt.sudoku.game.GameType;
-
 import static org.junit.Assert.*;
 
 /**
@@ -153,4 +150,45 @@ public class GameControllerTest {
         assertEquals(2, controller.getErrorList().size());
         assertEquals(result, controller.getErrorList().toString());
     }
+
+    @Test
+    public void deleteTest() {
+        controller.setValue(1, 2, 5);
+        assertEquals(5, controller.getValue(1, 2));
+        controller.deleteValue(1, 2);
+        assertEquals(0, controller.getValue(1, 2));
+    }
+
+    @Test
+    public void createNoteTest() {
+        controller.setNote(1, 2, 5);
+        controller.setNote(1, 2, 9);
+
+        boolean[] result = {false, false, false, false, true, false, false, false, true};
+
+        assertArrayEquals(result, controller.getNotes(1, 2));
+    }
+
+    @Test
+    public void deleteNoteTest() {
+        controller.setNote(1, 2, 5);
+        controller.setNote(1, 2, 9);
+        controller.deleteNote(1, 2, 5);
+
+        boolean[] result = {false, false, false, false, false, false, false, false, true};
+
+        assertArrayEquals(result, controller.getNotes(1, 2));
+    }
+
+    @Test
+    public void toggleNoteTest() {
+        controller.toggleNote(1,2,5);
+        controller.toggleNote(1,2,9);
+        controller.toggleNote(1,2,5);
+        controller.toggleNote(1,2,4);
+
+        boolean[] result = {false, false, false, true, false, false, false, false, true};
+
+        assertArrayEquals(result, controller.getNotes(1, 2));
+    }
 }