Æliens

  package
  {
   import flash.display.Sprite;
   import flash.events.Event;
  

   
   public class @tmp-@ax-animation-ch09-Bubbles2 extends Sprite
   {
    private var balls:Array;
    private var numBalls:Number = 30;
    private var bounce:Number = -0.5;
    private var spring:Number = 0.05;
    private var gravity:Number = 0.1;
    
  

    
    public function @tmp-@ax-animation-ch09-Bubbles2()
    {
     init();
    }
    
  

    private function init():void
    {
     balls = new Array();
     
     for(var i:uint = 0; i < numBalls; i++)
     {
      var ball:animation_ch09_Ball = new animation_ch09_Ball(Math.random() * 30 + 20, Math.random() * 0xffffff);
      ball.x = Math.random() * stage.stageWidth;
      ball.y = Math.random() * stage.stageHeight;
      ball.vx = Math.random() * 6 - 3;
      ball.vy = Math.random() * 6 - 3;
      addChild(ball);
      balls.push(ball);
     }
  

     
     addEventListener(Event.ENTER_FRAME, onEnterFrame);   
    }
  

    
    private function onEnterFrame(event:Event):void
    {
     for(var i:uint = 0; i < numBalls - 1; i++)
     {
      var ball0:animation_ch09_Ball = balls[i];
  

      for(var j:uint = i + 1; j < numBalls; j++)
      {
       var ball1:animation_ch09_Ball = balls[j];
       var dx:Number = ball1.x - ball0.x;
       var dy:Number = ball1.y - ball0.y;
       var dist:Number = Math.sqrt(dx * dx + dy * dy);
       var minDist:Number = ball0.radius + ball1.radius;
  

       if(dist < minDist)
       {
        var angle:Number = Math.atan2(dy, dx);
        var tx:Number = ball0.x + dx / dist * minDist;
        var ty:Number = ball0.y + dy / dist * minDist;
        var ax:Number = (tx - ball1.x) * spring;
        var ay:Number = (ty - ball1.y) * spring;
        ball0.vx -= ax;
        ball0.vy -= ay;
        ball1.vx += ax;
        ball1.vy += ay;
       }
      }
     }
     
  

     for(i = 0; i < numBalls; i++)
     {
      var ball:animation_ch09_Ball = balls[i];
      move(ball);
     }
    }
    
  

    private function move(ball:animation_ch09_Ball):void
    {
     ball.vy += gravity;
     ball.x += ball.vx;
     ball.y += ball.vy;
  

     if(ball.x + ball.radius > stage.stageWidth)
     {
      ball.x = stage.stageWidth - ball.radius;
      ball.vx *= bounce;
     }
     else if(ball.x - ball.radius < 0)
     {
      ball.x = ball.radius;
      ball.vx *= bounce;
     }
  

     if(ball.y + ball.radius > stage.stageHeight)
     {
      ball.y = stage.stageHeight - ball.radius;
      ball.vy *= bounce;
     }
     else if(ball.y - ball.radius < 0)
     {
      ball.y = ball.radius;
      ball.vy *= bounce;
     }
    }
   }
  }