PR suggestions

doc/examples/animations/lib/main.dart

@@ -20,8 +20,6 @@ class MyGame extends BaseGame {
   final animation = flame_animation.Animation.sequenced('chopper.png', 4,
       textureWidth: 48, textureHeight: 48, stepTime: 0.15);
 
-  Size screenSize;
-
   void addAnimation() {
     final animationComponent = AnimationComponent(100, 100, animation, destroyOnFinish: true);
     animationComponent.x = size.width / 2 - 50;
@@ -30,14 +28,16 @@ class MyGame extends BaseGame {
     add(animationComponent);
   }
 
-  MyGame(this.screenSize) {
+  MyGame(Size screenSize) {
+    size = screenSize;
+
     final animationComponent = AnimationComponent(100, 100, animation);
-    animationComponent.x = screenSize.width / 2 - 100;
+    animationComponent.x = size.width / 2 - 100;
     animationComponent.y = 100;
 
     final reversedAnimationComponent =
         AnimationComponent(100, 100, animation.reversed());
-    reversedAnimationComponent.x = screenSize.width / 2;
+    reversedAnimationComponent.x = size.width / 2;
     reversedAnimationComponent.y = 100;
 
     add(animationComponent);

doc/examples/aseprite/lib/main.dart

@@ -10,9 +10,8 @@ void main() async{
 }
 
 class MyGame extends BaseGame {
-  Size screenSize;
-
-  MyGame(this.screenSize) {
+  MyGame(Size screenSize) {
+    size = screenSize;
     _start();
   }
 
@@ -21,8 +20,8 @@ class MyGame extends BaseGame {
         'chopper.png', 'chopper.json');
     final animationComponent = AnimationComponent(200, 200, animation);
 
-    animationComponent.x = (screenSize.width / 2) - 100;
-    animationComponent.y = (screenSize.height / 2) - 100;
+    animationComponent.x = (size.width / 2) - 100;
+    animationComponent.y = (size.height / 2) - 100;
 
     add(animationComponent);
   }

doc/examples/sound/lib/main.dart

@@ -40,9 +40,8 @@ class Ball extends PositionComponent {
 }
 
 class MyGame extends BaseGame {
-  Size screenSize;
-
-  MyGame(this.screenSize) {
+  MyGame(Size screenSize) {
+    size = screenSize;
     _start();
   }
 
@@ -52,8 +51,8 @@ class MyGame extends BaseGame {
     Flame.audio.load('boin.mp3');
     Flame.audio.loop('music.mp3', volume: 0.4);
 
-    add(Ball(this.screenSize)
-      ..y = (this.screenSize.height / 2) - 50
+    add(Ball(size)
+      ..y = (size.height / 2) - 50
       ..width = 100
       ..height = 100);
   }

doc/examples/text/lib/main.dart

@@ -35,27 +35,26 @@ class MyTextBox extends TextBoxComponent {
 }
 
 class MyGame extends BaseGame {
-  Size screenSize;
-
-  MyGame(this.screenSize) {
+  MyGame(Size screenSize) {
+    size = screenSize;
     add(TextComponent('Hello, Flame', config: regular)
       ..anchor = Anchor.topCenter
-      ..x = screenSize.width / 2
+      ..x = size.width / 2
       ..y = 32.0);
 
     add(TextComponent('center', config: tiny)
       ..anchor = Anchor.center
-      ..x = screenSize.width / 2
-      ..y = screenSize.height / 2);
+      ..x = size.width / 2
+      ..y = size.height / 2);
 
     add(TextComponent('bottomRight', config: tiny)
       ..anchor = Anchor.bottomRight
-      ..x = screenSize.width
-      ..y = screenSize.height);
+      ..x = size.width
+      ..y = size.height);
 
     add(MyTextBox(
         'Lorem ipsum dolor sit amet, consectetur adipiscing elit. Etiam eget ligula eu lectus lobortis condimentum.')
       ..anchor = Anchor.bottomLeft
-      ..y = screenSize.height);
+      ..y = size.height);
   }
 }