Fix more Analyzer warnings in Atom

sky/sdk/example/game/lib/game_demo_world.dart

 part of game;
 
 const double _steeringThreshold = 0.0;
 const double _steeringMax = 150.0;
 
 // Random generator
 Math.Random _rand = new Math.Random();
 
 const double _gameSizeWidth = 1024.0;
 const double _gameSizeHeight = 1024.0;
 
 const double _shipRadius = 30.0;
 const double _lrgAsteroidRadius = 40.0;
 const double _medAsteroidRadius = 20.0;
 const double _smlAsteroidRadius = 10.0;
 const double _maxAsteroidSpeed = 1.0;
 
 const int _lifeTimeLaser = 50;
 
 const int _numStarsInStarField = 150;
 
 const int _numFramesShieldActive = 60 * 5;
 const int _numFramesShieldFlickers = 60;
 
 class GameDemoWorld extends NodeWithSize {
   // Images
-  Image _imgNebula;
+  sky.Image _imgNebula;
 
   SpriteSheet _spriteSheet;
 
   // Inputs
   double _joystickX = 0.0;
   double _joystickY = 0.0;
 
   Node _gameLayer;
 
   Ship _ship;
@@ skipping 56 matching lines @@
 
   void addShip() {
     Ship ship = new Ship(_spriteSheet["ship.png"]);
     ship.zPosition = 10.0;
     _gameLayer.addChild(ship);
     _ship = ship;
 
     _shield = new Sprite(_spriteSheet["shield.png"]);
     _shield.zPosition = 11.0;
     _shield.scale = 0.5;
-    _shield.transferMode = TransferMode.plus;
+    _shield.transferMode = sky.TransferMode.plus;
     _gameLayer.addChild(_shield);
 
     Action rotate = new ActionRepeatForever(new ActionTween((a) => _shield.rotation = a, 0.0, 360.0, 1.0));
     actions.run(rotate);
   }
 
   void addLaser() {
     Laser laser = new Laser(_spriteSheet["laser.png"], _ship);
     laser.zPosition = 8.0;
     laser.constrainProportions = true;
@@ skipping 40 matching lines @@
       posVar: new Point(10.0, 10.0),
       speed: 10.0,
       speedVar: 5.0
     );
     particlesFire.zPosition = 1011.0;
     explosionNode.addChild(particlesFire);
 
 
     // Add ring
     Sprite sprtRing = new Sprite(_spriteSheet["explosion_ring.png"]);
-    sprtRing.transferMode = TransferMode.plus;
+    sprtRing.transferMode = sky.TransferMode.plus;
     explosionNode.addChild(sprtRing);
 
     Action scale = new ActionTween( (a) => sprtRing.scale = a, 0.2, 1.0, 1.5);
     Action scaleAndRemove = new ActionSequence([scale, new ActionRemoveNode(sprtRing)]);
     Action fade = new ActionTween( (a) => sprtRing.opacity = a, 1.0, 0.0, 1.5);
     actions.run(scaleAndRemove);
     actions.run(fade);
 
     // Add streaks
     for (int i = 0; i < 5; i++) {
       Sprite sprtFlare = new Sprite(_spriteSheet["explosion_flare.png"]);
       sprtFlare.pivot = new Point(0.3, 1.0);
       sprtFlare.scaleX = 0.3;
-      sprtFlare.transferMode = TransferMode.plus;
+      sprtFlare.transferMode = sky.TransferMode.plus;
       sprtFlare.rotation = _rand.nextDouble() * 360.0;
       explosionNode.addChild(sprtFlare);
 
       double multiplier = _rand.nextDouble() * 0.3 + 1.0;
 
       Action scale = new ActionTween( (a) => sprtFlare.scaleY = a, 0.3 * multiplier, 0.8, 1.5 * multiplier);
       Action scaleAndRemove = new ActionSequence([scale, new ActionRemoveNode(sprtFlare)]);
       Action fadeIn = new ActionTween( (a) => sprtFlare.opacity = a, 0.0, 1.0, 0.5 * multiplier);
       Action fadeOut = new ActionTween( (a) => sprtFlare.opacity = a, 1.0, 0.0, 1.0 * multiplier);
       Action fadeInOut = new ActionSequence([fadeIn, fadeOut]);
@@ skipping 306 matching lines @@
 
 class Laser extends Sprite {
   int _frameCount = 0;
   Point _movementVector;
   double radius = 20.0;
 
   Laser(Texture img, Ship ship) : super(img) {
     size = new Size(30.0, 30.0);
     position = ship.position;
     rotation = ship.rotation + 90.0;
-    transferMode = TransferMode.plus;
+    transferMode = sky.TransferMode.plus;
     double rotRadians = convertDegrees2Radians(rotation);
     _movementVector = pointMult(new Point(Math.sin(rotRadians), -Math.cos(rotRadians)), 10.0);
     _movementVector = new Point(_movementVector.x + ship._movementVector[0], _movementVector.y + ship._movementVector[1]);
   }
 
   void move() {
     position = pointAdd(position, _movementVector);
     _frameCount++;
   }
 }
@@ skipping 17 matching lines @@
       _starPositions.add(new Point(_rand.nextDouble() * _gameSizeWidth, _rand.nextDouble() * _gameSizeHeight));
       _starScales.add(_rand.nextDouble());
       _opacity.add(_rand.nextDouble() * 0.5 + 0.5);
       _textures.add(spriteSheet["star_${_rand.nextInt(2)}.png"]);
     }
   }
 
   void paint(PaintingCanvas canvas) {
     // Setup paint object for opacity and transfer mode
     Paint paint = new Paint();
-    paint.setTransferMode(TransferMode.plus);
+    paint.setTransferMode(sky.TransferMode.plus);
 
     double baseScaleX = 64.0 / _textures[0].size.width;
     double baseScaleY = 64.0 / _textures[0].size.height;
 
     // Draw each star
     for (int i = 0; i < _numStars; i++) {
       Point pos = _starPositions[i];
       double scale = _starScales[i];
       paint.color = new Color.fromARGB((255.0*_opacity[i]).toInt(), 255, 255, 255);
 
@@ skipping 22 matching lines @@
       if (yPos >= _gameSizeHeight) yPos -= _gameSizeHeight;
       if (yPos < 0) yPos += _gameSizeHeight;
 
       _starPositions[i] = new Point(xPos, yPos);
     }
   }
 }
 
 class Nebula extends Node {
 
-  Nebula.withImage(Image img) {
+  Nebula.withImage(sky.Image img) {
     for (int i = 0; i < 2; i++) {
       for (int j = 0; j < 2; j++) {
         Sprite sprt = new Sprite.fromImage(img);
         sprt.pivot = Point.origin;
         sprt.position = new Point(i * _gameSizeWidth - _gameSizeWidth, j * _gameSizeHeight - _gameSizeHeight);
         addChild(sprt);
       }
     }
   }
 }
@@ skipping 22 matching lines @@
   double dy = a.y - b.y;
   if (dx < 0.0) dx = -dx;
   if (dy < 0.0) dy = -dy;
   if (dx > dy) {
     return dx + dy/2.0;
   }
   else {
     return dy + dx/2.0;
   }
 }