package {
 import flash.display.Sprite;
 import flash.events.Event;
 public class Bubbles2 extends Sprite {
  private var balls:Array;
  private var numBalls:Number=10;
  private var bounce:Number=-0.5;
  private var spring:Number=0.05;
  private var gravity:Number=0.1;
  public function Bubbles2() {
   init();
  }
  private function init():void {
   balls=new Array();

   for (var i:uint=0; i<numBalls; i++) {
    var ball:Ball=new 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:Ball=balls[i];
    for (var j:uint=i+1; j<numBalls; j++) {
     var ball1: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+Math.cos(angle)*minDist;
      var ty:Number=ball0.y+Math.sin(angle)*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:Ball = balls[i];
    move(ball);
   }
  }
  private function move(ball: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;
   }
  }
 }
}