flash on 2010-4-14

/**
 * Copyright kihon ( http://wonderfl.net/user/kihon )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/1C8y
 */

package
{
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.KeyboardEvent;
	import flash.geom.Point;
 
	public class Main extends Sprite
	{
		private var f:Number = 100;
		private var zpos:Number = 100;
		private var vp:Point = new Point(stage.stageWidth / 2, stage.stageHeight / 2);
		private var px:int = 0;
		private var py:int = 0;
		private var obj:Sprite;
 
		public function Main()
		{
			obj = new Sprite();
			obj.graphics.beginFill(0x0);
			obj.graphics.drawCircle(0, 0, 100);
			obj.graphics.endFill();
			obj.x = obj.y = 100;
			addChild(obj);
 
			stage.addEventListener(KeyboardEvent.KEY_DOWN, onKeyDown);
			addEventListener(Event.ENTER_FRAME, onEnterFrame);
		}
 
		private function onEnterFrame(event:Event):void
		{
			var scale:Number = f / (f + zpos);
			obj.scaleX = obj.scaleY = scale;
 
			obj.x = vp.x + px * scale;
			obj.y = vp.y + py * scale;
		}
 
		private function onKeyDown(event:KeyboardEvent):void 
		{
			if (event.keyCode == 38) zpos += 10;
			if (event.keyCode == 40) zpos -= 10;
		}
	}
}