I wanna play Rockman

/**
 * Copyright plus-tic ( http://wonderfl.net/user/plus-tic )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/rVh2
 */

package
{
    import flash.display.Bitmap;
    import flash.display.BitmapData;
    import flash.display.Loader;
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.events.KeyboardEvent;
    import flash.geom.Point;
    import flash.geom.Rectangle;
    import flash.net.URLRequest;
    import flash.system.LoaderContext;
 
    public class Main extends Sprite
    {
        private var charaChip:BitmapData;
        private const C_WIDTH:int = 31;//キャラの幅
        private const C_HEIGHT:int = 30;//キャラの高さ
        
        private var frame:int = 0;//時間制御用変数
        private var charaX:int = 0;//charaX軸
        private var charaY:int = 0;//charaY軸
        private var prevcy:int = 0;
        //copyPixelsで切り出したキャラを入れているBitmapData
        private var chara:BitmapData;
         
         private var left:Boolean = false;
         private var right:Boolean = false;    
         private const SPEED:int = 10;
         private var Rockman:Bitmap;
                  
         
        public function Main(){
            var loader:Loader = new Loader();
            loader.contentLoaderInfo.addEventListener(Event.INIT, initHandler);
            loader.load(new URLRequest
            ("http://assets.wonderfl.net/images/related_images/c/c6/c6d0/c6d025f7dd6b2bd96b138515d408767b398e1f02"),
            new LoaderContext(true));
        }
 
        private function initHandler(event:Event):void{
            // チップ画像読み込み
            var loader:Loader = event.currentTarget.loader;
            charaChip = new BitmapData(loader.width, loader.height, true, 0x0);
            charaChip.draw(loader);
            //背景透過処理
            charaChip.threshold(charaChip, charaChip.rect, new Point(), "==", 0xFF0000, 0x0, 0xFFFFFF);
            
            chara = new BitmapData(C_WIDTH, C_HEIGHT, true, 0x0);
            
            //デカイの作成
            Rockman = new Bitmap(chara);
            Rockman.scaleX = Rockman.scaleY = 3;
            Rockman.x = stage.stageWidth/2;
            Rockman.y = stage.stageHeight/2;
            addChild(Rockman);
            
            addEventListener(Event.ENTER_FRAME, onEnterFrame);
            stage.addEventListener(KeyboardEvent.KEY_DOWN,onKeyDown);
            stage.addEventListener(KeyboardEvent.KEY_UP,onKeyUp);            
        }
        
        private function onEnterFrame(event:Event):void{
            if (left)Rockman.x -= SPEED,charaY=7;
            else if(right)Rockman.x += SPEED,charaY=1;
            else if(!right||!left)charaY =0;
            
            if (prevcy != charaY || frame++ % 10 == 0){
                chara.copyPixels(charaChip, 
                    new Rectangle(C_WIDTH * (charaX+0) , C_HEIGHT * charaY , C_WIDTH,C_HEIGHT), new Point());
                charaX = (charaX + 1) % 3;
                prevcy = charaY;
            }
        }
        
        private function onKeyDown(event:KeyboardEvent):void{
            if (event.keyCode == 37) left = true;
            if (event.keyCode == 39) right = true;
        }
        
        private function onKeyUp(event:KeyboardEvent):void{
            if (event.keyCode == 37) left = false;
            if (event.keyCode == 39) right = false;
        }
        
    }
}