Æliens

    private function init():void
    {
     stage.align = StageAlign.TOP_LEFT;
     stage.scaleMode = StageScaleMode.NO_SCALE;
     
     ball = new animation_ch15_Ball(15);
     addChild(ball);
     addEventListener(Event.ENTER_FRAME, onEnterFrame);
    }
   

    private function onEnterFrame(event:Event):void
    {
     xpos += vx;
     ypos += vy;
     zpos += vz;
     
     var radius:Number =  ball.radius;
     if(xpos + radius > right)
     {
      xpos = right - radius;
      vx *= -1;
     }
     else if(xpos - radius < left)
     {
      xpos = left + radius;
      vx *= -1;
     }
     if(ypos + radius > bottom)
     {
      ypos = bottom - radius;
      vy *= -1;
     }
     else if(ypos - radius < top)
     {
      ypos = top + radius;
      vy *= -1;
     }
     if(zpos + radius > front)
     {
      zpos = front - radius;
      vz *= -1;
     }
     else if(zpos - radius < back)
     {
      zpos = back + radius;
      vz *= -1;
     }
    

     if(zpos > -fl)
     {
      var scale:Number = fl / (fl + zpos);
      ball.scaleX = ball.scaleY = scale;
      ball.x = vpX + xpos * scale;
      ball.y = vpY + ypos * scale;
      ball.visible = true;
     }
     else
     {
      ball.visible = false;
     }
    }
   }
  }