New game demo, initial version

examples/game/lib/main.dart

diff --git a/examples/game/lib/main.dart b/examples/game/lib/main.dart
index 1a6aeb6..1efda12 100644
--- a/examples/game/lib/main.dart
+++ b/examples/game/lib/main.dart
@@ -77,10 +77,19 @@
 class GameDemoApp extends App {
 
   NavigationState _navigationState;
-  GameDemoWorld _game;
+  NodeWithSize _game;
   int _lastScore = 0;
 
   void initState() {
+    // _game = new GameDemoNode(
+    //   _imageMap,
+    //   _spriteSheet,
+    //   _spriteSheetUI,
+    //   _sounds,
+    //   (lastScore) {
+    //     setState(() {_lastScore = lastScore;});
+    //   });
+
     _navigationState = new NavigationState([
       new Route(
         name: '/',
@@ -112,24 +121,23 @@
   }
 
   Widget _buildGameScene(navigator, route) {
-    return new SpriteWidget(_game);
+    return new SpriteWidget(_game, SpriteBoxTransformMode.fixedWidth);
   }
 
   Widget _buildMainScene(navigator, route) {
     return new Stack([
-      new SpriteWidget(new MainScreenBackground()),
+      new SpriteWidget(new MainScreenBackground(), SpriteBoxTransformMode.fixedWidth),
       new Flex([
         new TextureButton(
           onPressed: () {
-            _game = new GameDemoWorld(
-              _app,
-              navigator,
+            _game = new GameDemoNode(
               _imageMap,
               _spriteSheet,
               _spriteSheetUI,
               _sounds,
               (lastScore) {
                 setState(() {_lastScore = lastScore;});
+                navigator.pop();
               }
             );
             navigator.pushNamed('/game');
@@ -243,14 +251,19 @@
 }
 
 class MainScreenBackground extends NodeWithSize {
-  MainScreenBackground() : super(new Size(1024.0, 1024.0)) {
-    Sprite sprtBackground = new Sprite.fromImage(_imageMap['assets/starfield.png']);
-    sprtBackground.position = new Point(512.0, 512.0);
-    addChild(sprtBackground);
+  MainScreenBackground() : super(new Size(320.0, 320.0)) {
+    // Sprite sprtBackground = new Sprite.fromImage(_imageMap['assets/starfield.png']);
+    // sprtBackground.position = new Point(160.0, 160.0);
+    // addChild(sprtBackground);
 
     assert(_spriteSheet.image != null);
 
     StarField starField = new StarField(_spriteSheet, 200, true);
     addChild(starField);
   }
+
+  void paint(PaintingCanvas canvas) {
+    canvas.drawRect(new Rect.fromLTWH(0.0, 0.0, 320.0, 320.0), new Paint()..color=new Color(0xff000000));
+    super.paint(canvas);
+  }
 }