diff --git a/app/src/main/res/layout-land/content_main.xml b/app/src/main/res/layout-land/content_main.xml
index 2316b12..11fb806 100644
--- a/app/src/main/res/layout-land/content_main.xml
+++ b/app/src/main/res/layout-land/content_main.xml
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout
-    android:id="@+id/main_content"
+<LinearLayout android:id="@+id/main_content"
     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"
@@ -35,7 +34,7 @@
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:layout_marginTop="@dimen/activity_vertical_margin"
-            android:rotation="90"/>
+            android:rotation="90" />
 
         <ImageView
             android:id="@+id/mode_arrow_left"
@@ -47,18 +46,19 @@
             android:padding="@dimen/activity_vertical_margin"
             android:layout_centerHorizontal="true"
             android:onClick="onClick"
-            android:rotation="90"/>
+            android:rotation="90" />
+
         <ImageView
             android:id="@+id/mode_arrow_right"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:src="@drawable/ic_keyboard_arrow_right_black_24dp"
+            app:srcCompat="@drawable/ic_keyboard_arrow_right_black_24dp"
             android:layout_alignParentBottom="true"
             android:padding="@dimen/activity_vertical_margin"
             android:layout_marginEnd="@dimen/activity_horizontal_margin"
             android:layout_centerHorizontal="true"
             android:onClick="onClick"
-            android:rotation="90"/>
+            android:rotation="90" />
     </RelativeLayout>
 
     <RelativeLayout
@@ -81,30 +81,31 @@
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:layout_marginTop="@dimen/activity_vertical_margin"
-            android:rotation="90"/>
+            android:rotation="90" />
 
         <ImageView
             android:id="@+id/size_arrow_left"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_marginTop="@dimen/activity_vertical_margin"
-            android:src="@drawable/ic_keyboard_arrow_left_black_24dp"
+            app:srcCompat="@drawable/ic_keyboard_arrow_left_black_24dp"
             android:layout_alignParentTop="true"
             android:padding="@dimen/activity_vertical_margin"
             android:layout_centerHorizontal="true"
             android:onClick="onClick"
             android:rotation="90" />
+
         <ImageView
             android:id="@+id/size_arrow_right"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:src="@drawable/ic_keyboard_arrow_right_black_24dp"
+            app:srcCompat="@drawable/ic_keyboard_arrow_right_black_24dp"
             android:layout_alignParentBottom="true"
             android:padding="@dimen/activity_vertical_margin"
             android:layout_marginEnd="@dimen/activity_horizontal_margin"
             android:layout_centerHorizontal="true"
             android:onClick="onClick"
-            android:rotation="90"/>
+            android:rotation="90" />
     </RelativeLayout>
 
     <LinearLayout
@@ -122,7 +123,7 @@
             android:background="@drawable/button_normal"
             android:text="@string/main_button_quick_start"
             android:id="@+id/quick_start_button"
-            android:onClick="onClick"/>
+            android:onClick="onClick" />
 
         <Button
             android:layout_marginBottom="@dimen/activity_vertical_margin"
@@ -132,7 +133,7 @@
             android:background="@drawable/button_fullwidth"
             android:text="@string/custom_game"
             android:id="@+id/action_settings"
-            android:onClick="onClick"/>
+            android:onClick="onClick" />
 
     </LinearLayout>
 
diff --git a/app/src/main/res/layout-land/content_place_ship.xml b/app/src/main/res/layout-land/content_place_ship.xml
index 94d07a4..62e07a1 100644
--- a/app/src/main/res/layout-land/content_place_ship.xml
+++ b/app/src/main/res/layout-land/content_place_ship.xml
@@ -1,7 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
-    android:layout_height="match_parent">
+    android:layout_height="match_parent"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
 
     <GridView xmlns:android="http://schemas.android.com/apk/res/android"
         android:id="@+id/placement_gridview"
@@ -10,7 +11,7 @@
         android:verticalSpacing="1px"
         android:horizontalSpacing="1px"
         android:stretchMode="columnWidth"
-        android:layout_weight="1"/>
+        android:layout_weight="1" />
 
     <LinearLayout
         android:id="@+id/game_linear_layout"
@@ -31,10 +32,10 @@
                 android:id="@+id/arrow_left"
                 android:layout_width="50dp"
                 android:layout_height="wrap_content"
-                android:src="@drawable/arrow_left_black"
+                app:srcCompat="@drawable/arrow_left_black"
                 android:adjustViewBounds="true"
                 android:onClick="onClickButton"
-                android:layout_gravity="center_vertical"/>
+                android:layout_gravity="center_vertical" />
 
             <LinearLayout
                 android:layout_width="wrap_content"
@@ -46,19 +47,19 @@
                     android:id="@+id/arrow_up"
                     android:layout_width="50dp"
                     android:layout_height="wrap_content"
-                    android:src="@drawable/arrow_up_black"
+                    app:srcCompat="@drawable/arrow_up_black"
                     android:adjustViewBounds="true"
                     android:onClick="onClickButton"
-                    android:layout_weight="1"/>
+                    android:layout_weight="1" />
 
                 <ImageView
                     android:id="@+id/arrow_down"
                     android:layout_width="50dp"
                     android:layout_height="wrap_content"
-                    android:src="@drawable/arrow_down_black"
+                    app:srcCompat="@drawable/arrow_down_black"
                     android:adjustViewBounds="true"
                     android:onClick="onClickButton"
-                    android:layout_weight="1"/>
+                    android:layout_weight="1" />
 
             </LinearLayout>
 
@@ -66,10 +67,10 @@
                 android:id="@+id/arrow_right"
                 android:layout_width="50dp"
                 android:layout_height="wrap_content"
-                android:src="@drawable/arrow_right_black"
+                app:srcCompat="@drawable/arrow_right_black"
                 android:adjustViewBounds="true"
                 android:onClick="onClickButton"
-                android:layout_gravity="center_vertical"/>
+                android:layout_gravity="center_vertical" />
 
         </LinearLayout>
 
@@ -83,11 +84,11 @@
                 android:id="@+id/rotate_right"
                 android:layout_width="50dp"
                 android:layout_height="wrap_content"
-                android:src="@drawable/arrow_rotate_right_black"
+                app:srcCompat="@drawable/arrow_rotate_right_black"
                 android:adjustViewBounds="true"
                 android:onClick="onClickButton"
                 android:layout_weight="1"
-                android:layout_gravity="center_vertical"/>
+                android:layout_gravity="center_vertical" />
 
             <androidx.legacy.widget.Space
                 android:layout_width="50dp"
@@ -97,11 +98,11 @@
                 android:id="@+id/rotate_left"
                 android:layout_width="50dp"
                 android:layout_height="wrap_content"
-                android:src="@drawable/arrow_rotate_left_black"
+                app:srcCompat="@drawable/arrow_rotate_left_black"
                 android:adjustViewBounds="true"
                 android:onClick="onClickButton"
                 android:layout_weight="1"
-                android:layout_gravity="center_vertical"/>
+                android:layout_gravity="center_vertical" />
 
         </LinearLayout>
 
@@ -115,7 +116,7 @@
             android:layout_marginBottom="@dimen/activity_vertical_margin"
             android:background="@drawable/button_fullwidth"
             android:textColor="@color/white"
-            android:onClick="onClickReady"/>
+            android:onClick="onClickReady" />
 
     </LinearLayout>
 
diff --git a/app/src/main/res/layout-land/fragment_mode_main.xml b/app/src/main/res/layout-land/fragment_mode_main.xml
index 0fddf18..a78777d 100644
--- a/app/src/main/res/layout-land/fragment_mode_main.xml
+++ b/app/src/main/res/layout-land/fragment_mode_main.xml
@@ -1,8 +1,8 @@
-
 <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="match_parent"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:paddingLeft="@dimen/activity_horizontal_margin"
     android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingTop="@dimen/activity_vertical_margin"
@@ -13,7 +13,8 @@
     android:rotation="-90"
     tools:context="org.secuso.privacyfriendlybattleship.ui.MainActivity$GameModeFragment">
 
-    <TextView android:id="@+id/section_label"
+    <TextView
+        android:id="@+id/section_label"
         android:text="Label"
         android:textStyle="bold"
         android:textSize="18sp"
@@ -27,7 +28,7 @@
         android:layout_width="match_parent"
         android:adjustViewBounds="true"
         android:layout_centerInParent="true"
-        android:src="@drawable/ic_person_black_24px"
-        android:layout_height="0dp"/>
+        app:srcCompat="@drawable/ic_person_black_24px"
+        android:layout_height="0dp" />
 
 </LinearLayout>
\ No newline at end of file
diff --git a/app/src/main/res/layout-land/fragment_size_main.xml b/app/src/main/res/layout-land/fragment_size_main.xml
index 974c014..5bcc951 100644
--- a/app/src/main/res/layout-land/fragment_size_main.xml
+++ b/app/src/main/res/layout-land/fragment_size_main.xml
@@ -14,5 +14,5 @@
         android:layout_height="wrap_content"
         android:id="@+id/select_size"
         android:layout_weight="1"
-        android:gravity="center"/>
+        android:gravity="center" />
 </LinearLayout>
diff --git a/app/src/main/res/layout-xlarge/content_main.xml b/app/src/main/res/layout-xlarge/content_main.xml
index b43d721..80daf96 100644
--- a/app/src/main/res/layout-xlarge/content_main.xml
+++ b/app/src/main/res/layout-xlarge/content_main.xml
@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<LinearLayout
-    android:id="@+id/main_content"
+<LinearLayout android:id="@+id/main_content"
     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"
@@ -20,6 +19,7 @@
         android:layout_height="0dp"
         android:layoutDirection="ltr"
         android:layout_weight="4">
+
         <androidx.viewpager.widget.ViewPager
             android:id="@+id/modeScroller"
             android:layout_width="match_parent"
@@ -48,19 +48,20 @@
             android:layout_marginStart="@dimen/activity_horizontal_margin"
             android:layout_marginLeft="@dimen/activity_horizontal_margin"
             android:layout_centerVertical="true"
-            android:onClick="onClick"/>
+            android:onClick="onClick" />
+
         <ImageView
             android:id="@+id/mode_arrow_right"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:src="@drawable/ic_keyboard_arrow_right_black_24dp"
+            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"/>
+            android:onClick="onClick" />
     </RelativeLayout>
 
     <RelativeLayout
@@ -68,6 +69,7 @@
         android:layout_height="0dp"
         android:layoutDirection="ltr"
         android:layout_weight="4">
+
         <TextView
             android:id="@+id/title_size"
             android:layout_width="wrap_content"
@@ -89,26 +91,27 @@
             android:id="@+id/size_arrow_left"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:src="@drawable/ic_keyboard_arrow_left_black_24dp"
+            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"/>
+            android:onClick="onClick" />
+
         <ImageView
             android:id="@+id/size_arrow_right"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:src="@drawable/ic_keyboard_arrow_right_black_24dp"
+            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"/>
+            android:onClick="onClick" />
     </RelativeLayout>
 
     <Button
@@ -119,7 +122,7 @@
         android:background="@drawable/button_normal"
         android:text="@string/main_button_quick_start"
         android:id="@+id/quick_start_button"
-        android:onClick="onClick"/>
+        android:onClick="onClick" />
 
     <Button
         android:layout_width="match_parent"
@@ -128,6 +131,6 @@
         android:background="@drawable/button_fullwidth"
         android:text="@string/custom_game"
         android:id="@+id/action_settings"
-        android:onClick="onClick"/>
+        android:onClick="onClick" />
 
 </LinearLayout>
diff --git a/app/src/main/res/layout/content_main.xml b/app/src/main/res/layout/content_main.xml
index 965b6ce..769758b 100644
--- a/app/src/main/res/layout/content_main.xml
+++ b/app/src/main/res/layout/content_main.xml
@@ -7,10 +7,10 @@
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical"
-    android:paddingBottom="@dimen/activity_vertical_margin"
     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.privacyfriendlybattleship.ui.MainActivity">
 
@@ -41,11 +41,11 @@
             android:id="@+id/mode_arrow_left"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:layout_alignParentLeft="true"
             android:layout_alignParentStart="true"
+            android:layout_alignParentLeft="true"
             android:layout_centerVertical="true"
-            android:layout_marginLeft="@dimen/activity_horizontal_margin"
             android:layout_marginStart="@dimen/activity_horizontal_margin"
+            android:layout_marginLeft="@dimen/activity_horizontal_margin"
             android:onClick="onClick"
             android:padding="@dimen/activity_horizontal_margin"
             app:srcCompat="@drawable/ic_keyboard_arrow_left_black_24dp" />
@@ -61,7 +61,7 @@
             android:layout_marginRight="@dimen/activity_horizontal_margin"
             android:onClick="onClick"
             android:padding="@dimen/activity_horizontal_margin"
-            android:src="@drawable/ic_keyboard_arrow_right_black_24dp" />
+            app:srcCompat="@drawable/ic_keyboard_arrow_right_black_24dp" />
     </RelativeLayout>
 
     <RelativeLayout
@@ -91,14 +91,14 @@
             android:id="@+id/size_arrow_left"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:layout_alignParentLeft="true"
             android:layout_alignParentStart="true"
+            android:layout_alignParentLeft="true"
             android:layout_centerVertical="true"
-            android:layout_marginLeft="@dimen/activity_horizontal_margin"
             android:layout_marginStart="@dimen/activity_horizontal_margin"
+            android:layout_marginLeft="@dimen/activity_horizontal_margin"
             android:onClick="onClick"
             android:padding="@dimen/activity_horizontal_margin"
-            android:src="@drawable/ic_keyboard_arrow_left_black_24dp" />
+            app:srcCompat="@drawable/ic_keyboard_arrow_left_black_24dp" />
 
         <ImageView
             android:id="@+id/size_arrow_right"
@@ -111,7 +111,7 @@
             android:layout_marginRight="@dimen/activity_horizontal_margin"
             android:onClick="onClick"
             android:padding="@dimen/activity_horizontal_margin"
-            android:src="@drawable/ic_keyboard_arrow_right_black_24dp" />
+            app:srcCompat="@drawable/ic_keyboard_arrow_right_black_24dp" />
     </RelativeLayout>
 
     <Button
diff --git a/app/src/main/res/layout/content_place_ship.xml b/app/src/main/res/layout/content_place_ship.xml
index e816916..97228a8 100644
--- a/app/src/main/res/layout/content_place_ship.xml
+++ b/app/src/main/res/layout/content_place_ship.xml
@@ -1,7 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
-    android:layout_height="match_parent">
+    android:layout_height="match_parent"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
 
     <GridView xmlns:android="http://schemas.android.com/apk/res/android"
         android:id="@+id/placement_gridview"
@@ -12,7 +13,7 @@
         android:verticalSpacing="1dp"
         android:horizontalSpacing="1dp"
         android:stretchMode="columnWidth"
-        android:gravity="center"/>
+        android:gravity="center" />
 
     <LinearLayout
         android:id="@+id/game_linear_layout"
@@ -27,10 +28,10 @@
             android:id="@+id/arrow_left"
             android:layout_width="50dp"
             android:layout_height="wrap_content"
-            android:src="@drawable/arrow_left_black"
+            app:srcCompat="@drawable/arrow_left_black"
             android:adjustViewBounds="true"
             android:onClick="onClickButton"
-            android:layout_gravity="center_vertical"/>
+            android:layout_gravity="center_vertical" />
 
         <LinearLayout
             android:layout_width="wrap_content"
@@ -42,19 +43,19 @@
                 android:id="@+id/arrow_up"
                 android:layout_width="50dp"
                 android:layout_height="wrap_content"
-                android:src="@drawable/arrow_up_black"
+                app:srcCompat="@drawable/arrow_up_black"
                 android:adjustViewBounds="true"
                 android:onClick="onClickButton"
-                android:layout_weight="1"/>
+                android:layout_weight="1" />
 
             <ImageView
                 android:id="@+id/arrow_down"
                 android:layout_width="50dp"
                 android:layout_height="wrap_content"
-                android:src="@drawable/arrow_down_black"
+                app:srcCompat="@drawable/arrow_down_black"
                 android:adjustViewBounds="true"
                 android:onClick="onClickButton"
-                android:layout_weight="1"/>
+                android:layout_weight="1" />
 
         </LinearLayout>
 
@@ -62,10 +63,10 @@
             android:id="@+id/arrow_right"
             android:layout_width="50dp"
             android:layout_height="wrap_content"
-            android:src="@drawable/arrow_right_black"
+            app:srcCompat="@drawable/arrow_right_black"
             android:adjustViewBounds="true"
             android:onClick="onClickButton"
-            android:layout_gravity="center_vertical"/>
+            android:layout_gravity="center_vertical" />
 
         <LinearLayout
             android:layout_width="wrap_content"
@@ -77,21 +78,21 @@
                 android:id="@+id/rotate_right"
                 android:layout_width="50dp"
                 android:layout_height="wrap_content"
-                android:src="@drawable/arrow_rotate_right_black"
+                app:srcCompat="@drawable/arrow_rotate_right_black"
                 android:adjustViewBounds="true"
                 android:onClick="onClickButton"
                 android:layout_weight="1"
-                android:layout_gravity="center_vertical"/>
+                android:layout_gravity="center_vertical" />
 
             <ImageView
                 android:id="@+id/rotate_left"
                 android:layout_width="50dp"
                 android:layout_height="wrap_content"
-                android:src="@drawable/arrow_rotate_left_black"
+                app:srcCompat="@drawable/arrow_rotate_left_black"
                 android:adjustViewBounds="true"
                 android:onClick="onClickButton"
                 android:layout_weight="1"
-                android:layout_gravity="center_vertical"/>
+                android:layout_gravity="center_vertical" />
 
         </LinearLayout>
 
@@ -105,8 +106,7 @@
             android:textColor="@color/white"
             android:layout_marginLeft="@dimen/activity_horizontal_margin"
             android:onClick="onClickReady"
-            android:layout_weight="1"
-            />
+            android:layout_weight="1" />
 
     </LinearLayout>
 
diff --git a/app/src/main/res/layout/fragment_mode_main.xml b/app/src/main/res/layout/fragment_mode_main.xml
index 25badc3..54ee192 100644
--- a/app/src/main/res/layout/fragment_mode_main.xml
+++ b/app/src/main/res/layout/fragment_mode_main.xml
@@ -1,8 +1,8 @@
-
 <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="match_parent"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:paddingLeft="@dimen/activity_horizontal_margin"
     android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingTop="@dimen/activity_vertical_margin"
@@ -12,7 +12,8 @@
     android:weightSum="8"
     tools:context="org.secuso.privacyfriendlybattleship.ui.MainActivity$GameModeFragment">
 
-    <TextView android:id="@+id/section_label"
+    <TextView
+        android:id="@+id/section_label"
         android:text="Label"
         android:textStyle="bold"
         android:textSize="18sp"
@@ -26,7 +27,7 @@
         android:layout_width="match_parent"
         android:adjustViewBounds="true"
         android:layout_centerInParent="true"
-        android:src="@drawable/ic_person_black_24px"
+        app:srcCompat="@drawable/ic_person_black_24px"
         android:layout_height="0dp" />
 
 </LinearLayout>
\ No newline at end of file
diff --git a/app/src/main/res/layout/fragment_size_main.xml b/app/src/main/res/layout/fragment_size_main.xml
index 28436d9..b593231 100644
--- a/app/src/main/res/layout/fragment_size_main.xml
+++ b/app/src/main/res/layout/fragment_size_main.xml
@@ -13,5 +13,5 @@
         android:layout_height="wrap_content"
         android:id="@+id/select_size"
         android:layout_weight="1"
-        android:gravity="center"/>
+        android:gravity="center" />
 </LinearLayout>