AS3基礎：圓周運動

package  
{
	import flash.display.Sprite;
	import flash.events.Event;
	
	/**
	 * ...
	 * @author hacker47
	 */
	public class Main extends Sprite 
	{
		private var angle:Number = 0;
		private var centerX:Number = 300;
		private var centerY:Number = 300;
		private var radius:Number = 200;
		private var speed:Number = .1;
		
		public function Main() 
		{
			if (stage) init();
			else
			addEventListener(Event.ADDED_TO_STAGE, init);
		}
		
		private function init(e:Event = null):void {
			addEventListener(Event.ENTER_FRAME, running);
		}
		
		private function running(e:Event):void {
			ball.x = centerX + Math.cos(angle) * radius;
			ball.y = centerY + Math.sin(angle) * radius;
			angle += speed;
		}
		
	}

}