private function fadeCircle(event:Event):void{
          circle.alpha -= fade;
          if (circle.alpha <= 0){
              fade = -fade;
              circle.alpha = 0.05;
          }
          else if (circle.alpha > 1){
              fade = -fade;
              circle.alpha = 0.95;
          }
      }
      
     ]]>
  </mx:Script>