飘雪效果的swf

//第一帧响应事件
import flash.events.Event;

addEventListener(Event.ENTER_FRAME,webcyz);

function webcyz(e:Event)
{

var xuehua:xue= new xue();
      xuehua.alpha = Math.random()+0.5;
      xuehua.height = xuehua.width = Math.random()*6+5;
      xuehua.x=Math.random()*550;

piaoxuekongjian.addChild(xuehua);

for(var i:int=0;i<piaoxuekongjian.numChildren;i++)
{
      var mc:xue = xue(piaoxuekongjian.getChildAt(i));

if(mc.y>420)
{
piaoxuekongjian.removeChild(mc);
i--;
}
else
{
      mc.y+=Math.random()*5+2;
      mc.x+=(Math.random()-.5)*10;
}
}

//雪花类，继承自影片剪辑

package {

import flash.display.MovieClip;

public class xue extends MovieClip {

public function xue() {
            // constructor code
      }
}

}

}