Adds particle systems to sprites

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;
@@ skipping 72 matching lines @@
   void addShip() {
     Ship ship = new Ship(_spriteSheet["ship.png"]);
     ship.zPosition = 10.0;
     _gameLayer.addChild(ship);
     _ship = ship;
   }
 
   void addLaser() {
     Laser laser = new Laser(_spriteSheet["laser.png"], _ship);
     laser.zPosition = 8.0;
+    laser.constrainProportions = true;
     _lasers.add(laser);
     _gameLayer.addChild(laser);
   }
 
   void addNebula() {
     _nebula = new Nebula.withImage(_imgNebula);
     _gameLayer.addChild(_nebula);
   }
-  
+
+  void addExplosion(AsteroidSize asteroidSize, Point position) {
+    // Add particles
+    ParticleSystem particles = new ParticleSystem(_spriteSheet["laser.png"], rotateToMovement: true,

[eseidel, 2015/06/30 01:04:50]

I'm not sure what the dart style is, but I would have indented this like:

particles = new ParticleSystem(
   foo: bar,
   baz: fla,
   yolo: blob
);

+    startRotation:90.0, startRotationVar: 0.0, endRotation: 90.0, startSize: 0.2, startSizeVar: 0.1, endSize: 0.2, endSizeVar: 0.1,
+    numParticlesToEmit: 25, emissionRate:1000.0, blueVar: 127);
+    particles.zPosition = 1010.0;
+    particles.position = position;
+    _gameLayer.addChild(particles);
+  }
+
   void update(double dt) {
     // Move asteroids
     for (Asteroid asteroid in _asteroids) {
       asteroid.position = pointAdd(asteroid.position, asteroid._movementVector);
     }
 
     // Move lasers and remove expired lasers
     for (int i = _lasers.length - 1; i >= 0; i--) {
       Laser laser = _lasers[i];
       laser.move();
@@ skipping 19 matching lines @@
       for (int j = _asteroids.length - 1; j >= 0; j--) {
         // Iterate over all the asteroids
         Asteroid asteroid = _asteroids[j];
 
         // Check for collision
         if (pointQuickDist(laser.position, asteroid.position) < laser.radius + asteroid.radius) {
           // Remove laser
           laser.removeFromParent();
           _lasers.removeAt(i);
 
-          // Add asteroids
+          // Add asteroids and explosions
           if (asteroid._asteroidSize == AsteroidSize.large) {
             for (int a = 0; a < 3; a++) addAsteroid(AsteroidSize.medium, asteroid.position);
           }
           else if (asteroid._asteroidSize == AsteroidSize.medium) {
             for (int a = 0; a < 5; a++) addAsteroid(AsteroidSize.small, asteroid.position);
           }
 
+          addExplosion(asteroid._asteroidSize, asteroid.position);
+
           // Remove asteroid
           asteroid.removeFromParent();
           _asteroids.removeAt(j);
           break;
         }
       }
     }
 
     // Move objects to center camera and warp objects around the edges
     centerCamera();
@@ skipping 167 matching lines @@
     position = new Point(position.x + _movementVector[0], position.y + _movementVector[1]);
     _movementVector.scale(0.9);
 
     rotation = dampenRotation(rotation, _rotationTarget, 0.1);
   }
 }
 
 class Laser extends Sprite {
   int _frameCount = 0;
   Point _movementVector;
-  double radius = 10.0;
+  double radius = 20.0;
 
   Laser(Texture img, Ship ship) : super(img) {
-    size = new Size(20.0, 20.0);
+    size = new Size(30.0, 30.0);
     position = ship.position;
     rotation = ship.rotation + 90.0;
     transferMode = 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);
@@ skipping 104 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;
   }
 }