diff --git a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuKeyboardLayout.java b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuKeyboardLayout.java
index f54aca5..3b8f603 100644
--- a/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuKeyboardLayout.java
+++ b/app/src/main/java/org/secuso/privacyfriendlysudoku/ui/view/SudokuKeyboardLayout.java
@@ -22,6 +22,7 @@ import android.util.AttributeSet;
 import android.util.TypedValue;
 import android.view.Gravity;
 import android.view.View;
+import android.view.ViewGroup;
 import android.widget.LinearLayout;
 
 import org.secuso.privacyfriendlysudoku.controller.GameController;
@@ -81,7 +82,7 @@ public class SudokuKeyboardLayout extends LinearLayout implements IHighlightChan
             if(orientation == LinearLayout.HORIZONTAL) {
                 p = new LayoutParams(LayoutParams.MATCH_PARENT, 0, 1);
             } else {
-                p = new LayoutParams(0, LayoutParams.MATCH_PARENT, 1);
+                p = new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.MATCH_PARENT, 1);
             }
             //if (i == 0) p.bottomMargin=10; else p.topMargin=10;
             p.setMargins(0, 5, 0, 5);
@@ -128,6 +129,7 @@ public class SudokuKeyboardLayout extends LinearLayout implements IHighlightChan
                 buttons[buttonIndex].setBackgroundResource(R.drawable.mnenomic_numpad_button);
                 buttons[buttonIndex].setPadding(0, 0, 0, 0);
                 buttons[buttonIndex].setGravity(Gravity.CENTER);
+                buttons[buttonIndex].setMinHeight((int) (normalTextSize * 2));
                 buttons[buttonIndex].setText(Symbol.getSymbol(symbolsToUse, buttonIndex));
                 buttons[buttonIndex].setTextSize(TypedValue.COMPLEX_UNIT_SP, normalTextSize);
                 buttons[buttonIndex].setValue(buttonIndex + 1);
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 bf01a21..b51d1fc 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
@@ -136,11 +136,11 @@ public class SudokuSpecialButtonLayout extends LinearLayout implements IHighligh
         for (SudokuButtonType t : getSpecialButtons()){
             fixedButtons[i] = new SudokuSpecialButton(getContext(),null);
             if(orientation == LinearLayout.HORIZONTAL) {
-                p = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT, 1);
+                p = new LayoutParams(0, LayoutParams.MATCH_PARENT, 1);
             } else {
-                p = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT, 1);
-                fixedButtons[i].setPadding(25, 0, 25, 0);
+                p = new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, 0, 1);
             }
+            fixedButtons[i].setPadding(25, 0, 25, 0);
             p.setMargins(5, 5, 5, 5);
 
             //int width2 =width/(fixedButtonsCount);
@@ -148,28 +148,16 @@ public class SudokuSpecialButtonLayout extends LinearLayout implements IHighligh
             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].setImageDrawable(ContextCompat.getDrawable(context, fixedButtons[i].getType().getResID()));
+            fixedButtons[i].setScaleType(ImageView.ScaleType.FIT_XY);
             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++;
         }
 
diff --git a/app/src/main/res/layout-land/content_game_view.xml b/app/src/main/res/layout-land/content_game_view.xml
index d9310a1..2af36d7 100644
--- a/app/src/main/res/layout-land/content_game_view.xml
+++ b/app/src/main/res/layout-land/content_game_view.xml
@@ -1,54 +1,63 @@
 <?xml version="1.0" encoding="utf-8"?>
-<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
-    android:layoutDirection="ltr"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/main_content"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    android:id="@+id/main_content"
+    android:layout_marginTop="?android:actionBarSize"
     android:paddingLeft="@dimen/activity_horizontal_margin"
-    android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingTop="@dimen/activity_vertical_margin"
+    android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingBottom="@dimen/activity_vertical_margin"
-    app:layout_behavior="@string/appbar_scrolling_view_behavior">
+    tools:context="org.secuso.privacyfriendlysudoku.ui.GameActivity">
 
         <org.secuso.privacyfriendlysudoku.ui.view.SudokuSpecialButtonLayout
             android:id="@+id/sudokuSpecialLayout"
-            android:layout_width="wrap_content"
-            android:layout_alignParentLeft="true"
-            android:layout_alignParentStart="true"
-            android:layout_marginLeft="15dp"
-            android:layout_marginStart="15dp"
-            android:layout_marginRight="30dp"
-            android:layout_marginEnd="30dp"
-            android:orientation="vertical"
-            android:layoutDirection="ltr"
+            android:layout_width="0dp"
             android:layout_height="match_parent"
-            android:gravity="center"/>
+            android:layout_weight="1"
+            android:layout_marginStart="0dp"
+            android:gravity="center"
+            android:orientation="vertical"
+            android:weightSum="1"
+            app:layout_constraintHorizontal_weight="1"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toStartOf="@+id/sudokuLayout"
+            app:layout_constraintHorizontal_bias="0.0"
+            app:layout_constraintStart_toStartOf="parent"
+            app:layout_constraintTop_toTopOf="parent"
+            android:layout_marginLeft="0dp" />
 
         <org.secuso.privacyfriendlysudoku.ui.view.SudokuFieldLayout
             android:id="@+id/sudokuLayout"
-            android:layout_width="wrap_content"
-            android:layout_height="match_parent"
-            android:layout_toRightOf="@+id/sudokuSpecialLayout"
-            android:layout_toEndOf="@+id/sudokuSpecialLayout"
-            android:minWidth="100dp"
+            android:layout_width="0dp"
+            android:layout_height="0dp"
             android:clickable="true"
-            android:gravity="center" />
+            android:focusable="true"
+            android:gravity="center"
+            app:layout_constraintHorizontal_weight="4"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintDimensionRatio="h,1:1"
+            app:layout_constraintEnd_toStartOf="@+id/sudokuKeyboardLayout"
+            app:layout_constraintHorizontal_bias="0.5"
+            app:layout_constraintStart_toEndOf="@+id/sudokuSpecialLayout"
+            app:layout_constraintTop_toTopOf="parent" />
 
         <org.secuso.privacyfriendlysudoku.ui.view.SudokuKeyboardLayout
-            android:layout_width="wrap_content"
-            android:layout_height="match_parent"
-            android:layout_marginLeft="30dp"
-            android:layout_marginStart="30dp"
-            android:layout_marginRight="15dp"
-            android:layout_marginEnd="15dp"
-            android:layout_alignParentRight="true"
-            android:layout_alignParentEnd="true"
-            android:layout_toRightOf="@+id/sudokuLayout"
-            android:layout_toEndOf="@+id/sudokuLayout"
             android:id="@+id/sudokuKeyboardLayout"
+            android:layout_width="0dp"
+            android:layout_height="match_parent"
+            android:layout_weight="2"
+            android:minWidth="50dp"
+            android:minHeight="50dp"
             android:orientation="horizontal"
-            android:weightSum="2"/>
+            android:weightSum="2"
+            app:layout_constraintBottom_toBottomOf="parent"
+            app:layout_constraintEnd_toEndOf="parent"
+            app:layout_constraintHorizontal_bias="0.5"
+            app:layout_constraintHorizontal_weight="2"
+            app:layout_constraintStart_toEndOf="@+id/sudokuLayout"
+            app:layout_constraintTop_toTopOf="parent" />
 
-</RelativeLayout>
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/app/src/main/res/layout-land/content_game_view_create_sudoku.xml b/app/src/main/res/layout-land/content_game_view_create_sudoku.xml
index edba24d..7fb15c7 100644
--- a/app/src/main/res/layout-land/content_game_view_create_sudoku.xml
+++ b/app/src/main/res/layout-land/content_game_view_create_sudoku.xml
@@ -1,57 +1,63 @@
 <?xml version="1.0" encoding="utf-8"?>
-<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools"
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
-    android:layoutDirection="ltr"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/main_content"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
-    android:id="@+id/main_content"
+    android:layout_marginTop="?android:actionBarSize"
     android:paddingLeft="@dimen/activity_horizontal_margin"
-    android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingTop="@dimen/activity_vertical_margin"
+    android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingBottom="@dimen/activity_vertical_margin"
-    app:layout_behavior="@string/appbar_scrolling_view_behavior">
+    tools:context="org.secuso.privacyfriendlysudoku.ui.GameActivity">
+
+    <org.secuso.privacyfriendlysudoku.ui.view.CreateSudokuSpecialButtonLayout
+        android:id="@+id/createSudokuLayout"
+        android:layout_width="0dp"
+        android:layout_height="match_parent"
+        android:layout_weight="1"
+        android:layout_marginStart="0dp"
+        android:gravity="center"
+        android:orientation="vertical"
+        android:weightSum="1"
+        app:layout_constraintHorizontal_weight="1"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toStartOf="@+id/sudokuLayout"
+        app:layout_constraintHorizontal_bias="0.0"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        android:layout_marginLeft="0dp" />
 
     <org.secuso.privacyfriendlysudoku.ui.view.SudokuFieldLayout
         android:id="@+id/sudokuLayout"
-        android:layout_width="wrap_content"
-        android:layout_height="match_parent"
-        android:layout_toRightOf="@+id/createSudokuLayout"
-        android:layout_toEndOf="@+id/createSudokuLayout"
-        android:minWidth="100dp"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
         android:clickable="true"
-        android:gravity="center" />
+        android:focusable="true"
+        android:gravity="center"
+        app:layout_constraintHorizontal_weight="4"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintDimensionRatio="h,1:1"
+        app:layout_constraintEnd_toStartOf="@+id/sudokuKeyboardLayout"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintStart_toEndOf="@+id/createSudokuLayout"
+        app:layout_constraintTop_toTopOf="parent" />
 
-        <org.secuso.privacyfriendlysudoku.ui.view.SudokuKeyboardLayout
-            android:layout_width="wrap_content"
-            android:layout_height="match_parent"
-            android:layout_marginLeft="30dp"
-            android:layout_marginStart="30dp"
-            android:layout_marginRight="15dp"
-            android:layout_marginEnd="15dp"
-            android:layout_alignParentRight="true"
-            android:layout_alignParentEnd="true"
-            android:layout_toRightOf="@+id/sudokuLayout"
-            android:layout_toEndOf="@+id/sudokuLayout"
-            android:id="@+id/sudokuKeyboardLayout"
-            android:orientation="horizontal"
-            android:weightSum="2">
+    <org.secuso.privacyfriendlysudoku.ui.view.SudokuKeyboardLayout
+        android:id="@+id/sudokuKeyboardLayout"
+        android:layout_width="0dp"
+        android:layout_height="match_parent"
+        android:layout_weight="2"
+        android:minWidth="50dp"
+        android:minHeight="50dp"
+        android:orientation="horizontal"
+        android:weightSum="2"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintHorizontal_bias="0.5"
+        app:layout_constraintHorizontal_weight="2"
+        app:layout_constraintStart_toEndOf="@+id/sudokuLayout"
+        app:layout_constraintTop_toTopOf="parent" />
 
-        </org.secuso.privacyfriendlysudoku.ui.view.SudokuKeyboardLayout>
-
-        <org.secuso.privacyfriendlysudoku.ui.view.CreateSudokuSpecialButtonLayout
-            android:id="@+id/createSudokuLayout"
-            android:layout_width="wrap_content"
-            android:layout_alignParentLeft="true"
-            android:layout_alignParentStart="true"
-            android:layout_marginLeft="15dp"
-            android:layout_marginStart="15dp"
-            android:layout_marginRight="30dp"
-            android:layout_marginEnd="30dp"
-            android:orientation="vertical"
-            android:layoutDirection="ltr"
-            android:layout_height="match_parent"
-            android:gravity="center">
-        </org.secuso.privacyfriendlysudoku.ui.view.CreateSudokuSpecialButtonLayout>
-
-</RelativeLayout>
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/app/src/main/res/layout/content_game_view.xml b/app/src/main/res/layout/content_game_view.xml
index 59b10f7..134c0bf 100644
--- a/app/src/main/res/layout/content_game_view.xml
+++ b/app/src/main/res/layout/content_game_view.xml
@@ -1,50 +1,59 @@
 <?xml version="1.0" encoding="utf-8"?>
-<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<androidx.constraintlayout.widget.ConstraintLayout
+    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:id="@+id/main_content"
+    android:layout_marginTop="?android:actionBarSize"
     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:context="org.secuso.privacyfriendlysudoku.ui.GameActivity">
 
     <org.secuso.privacyfriendlysudoku.ui.view.SudokuFieldLayout
         android:id="@+id/sudokuLayout"
-        android:layout_width="match_parent"
-        android:layoutDirection="ltr"
-        android:layout_height="wrap_content"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        android:layout_marginBottom="8dp"
         android:clickable="true"
-        android:gravity="center" />
+        android:focusable="true"
+        android:gravity="center"
+        app:layout_constraintBottom_toTopOf="@+id/sudokuButtonLayout"
+        app:layout_constraintDimensionRatio="1:1"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
 
     <LinearLayout
-        android:layout_width="fill_parent"
-        android:layout_height="fill_parent"
-        android:layout_below="@+id/sudokuLayout"
+        android:id="@+id/sudokuButtonLayout"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:minHeight="200dp"
         android:orientation="vertical"
-        android:weightSum="3">
+        android:weightSum="3"
+        app:layout_constraintTop_toBottomOf="@id/sudokuLayout"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent">
 
         <org.secuso.privacyfriendlysudoku.ui.view.SudokuKeyboardLayout
+            android:id="@+id/sudokuKeyboardLayout"
             android:layout_width="fill_parent"
             android:layout_height="0px"
-            android:id="@+id/sudokuKeyboardLayout"
-            android:orientation="vertical"
             android:layout_weight="2"
-            android:weightSum="2">
-
-        </org.secuso.privacyfriendlysudoku.ui.view.SudokuKeyboardLayout>
+            android:orientation="vertical"
+            android:weightSum="2" />
 
         <org.secuso.privacyfriendlysudoku.ui.view.SudokuSpecialButtonLayout
             android:id="@+id/sudokuSpecialLayout"
             android:layout_width="fill_parent"
             android:layout_height="0dp"
-            android:layout_weight="1">
-
-        </org.secuso.privacyfriendlysudoku.ui.view.SudokuSpecialButtonLayout>
+            android:layout_weight="1"
+            android:weightSum="1" />
 
     </LinearLayout>
 
-</RelativeLayout>
+</androidx.constraintlayout.widget.ConstraintLayout>
diff --git a/app/src/main/res/layout/content_game_view_create_sudoku.xml b/app/src/main/res/layout/content_game_view_create_sudoku.xml
index ff2d71c..cb69830 100644
--- a/app/src/main/res/layout/content_game_view_create_sudoku.xml
+++ b/app/src/main/res/layout/content_game_view_create_sudoku.xml
@@ -1,50 +1,59 @@
 <?xml version="1.0" encoding="utf-8"?>
-<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<androidx.constraintlayout.widget.ConstraintLayout
+    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:id="@+id/main_content"
+    android:layout_marginTop="?android:actionBarSize"
     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:context="org.secuso.privacyfriendlysudoku.ui.GameActivity">
 
     <org.secuso.privacyfriendlysudoku.ui.view.SudokuFieldLayout
         android:id="@+id/sudokuLayout"
-        android:layout_width="match_parent"
-        android:layoutDirection="ltr"
-        android:layout_height="wrap_content"
+        android:layout_width="0dp"
+        android:layout_height="0dp"
+        android:layout_marginBottom="8dp"
         android:clickable="true"
-        android:gravity="center" />
+        android:focusable="true"
+        android:gravity="center"
+        app:layout_constraintBottom_toTopOf="@+id/sudokuButtonLayout"
+        app:layout_constraintDimensionRatio="1:1"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
 
     <LinearLayout
-        android:layout_width="fill_parent"
-        android:layout_height="fill_parent"
-        android:layout_below="@+id/sudokuLayout"
+        android:id="@+id/sudokuButtonLayout"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:minHeight="200dp"
         android:orientation="vertical"
-        android:weightSum="3">
+        android:weightSum="3"
+        app:layout_constraintTop_toBottomOf="@id/sudokuLayout"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent">
 
         <org.secuso.privacyfriendlysudoku.ui.view.SudokuKeyboardLayout
+            android:id="@+id/sudokuKeyboardLayout"
             android:layout_width="fill_parent"
             android:layout_height="0px"
-            android:id="@+id/sudokuKeyboardLayout"
-            android:orientation="vertical"
             android:layout_weight="2"
-            android:weightSum="2">
-
-        </org.secuso.privacyfriendlysudoku.ui.view.SudokuKeyboardLayout>
+            android:orientation="vertical"
+            android:weightSum="2" />
 
         <org.secuso.privacyfriendlysudoku.ui.view.CreateSudokuSpecialButtonLayout
             android:id="@+id/createSudokuLayout"
             android:layout_width="fill_parent"
             android:layout_height="0dp"
-            android:layout_weight="1">
-
-        </org.secuso.privacyfriendlysudoku.ui.view.CreateSudokuSpecialButtonLayout>
+            android:layout_weight="1"
+            android:weightSum="1" />
 
     </LinearLayout>
 
-</RelativeLayout>
+</androidx.constraintlayout.widget.ConstraintLayout>