package
  {
          import flash.display.Sprite;
          import flash.events.Event;
          import flash.display.StageScaleMode;
          import flash.display.StageAlign;
  
          public class @ax-animation-ch11-Billiard2 extends Sprite
          {
                  private var ball0:animation_ch11_Ball;
                  private var ball1:animation_ch11_Ball;
                  
                  public function @ax-animation-ch11-Billiard2()
                  {
                          init();
                  }
                  
                  private function init():void
                  {
                          stage.scaleMode = StageScaleMode.NO_SCALE;
                          stage.align = StageAlign.TOP_LEFT;
                          ball0 = new animation_ch11_Ball(40);
                          ball0.mass = 2;
                          ball0.x = 50;
                          ball0.y = stage.stageHeight / 2;
                          ball0.vx = 1;
                          addChild(ball0);
  
                          ball1 = new animation_ch11_Ball(25);
                          ball1.mass = 1
                          ball1.x = 300;
                          ball1.y = stage.stageHeight / 2;
                          ball1.vx = -1;
                          addChild(ball1);
  
                          addEventListener(Event.ENTER_FRAME, onEnterFrame);
                  }
                  
                  private function onEnterFrame(event:Event):void
                  {
                          ball0.x += ball0.vx;
                          ball1.x += ball1.vx;
                          var dist:Number = ball1.x - ball0.x;
                          if(Math.abs(dist) < ball0.radius + ball1.radius)
                          {
                                  var vxTotal:Number = ball0.vx - ball1.vx;
                                  ball0.vx = ((ball0.mass - ball1.mass) * ball0.vx + 2 * ball1.mass * ball1.vx) / (ball0.mass + ball1.mass);
                                  ball1.vx = vxTotal + ball0.vx;
                                    
                                  ball0.x += ball0.vx;
                                  ball1.x += ball1.vx;
                          }
                  }
          }
  }