[D12]

package {
////////	
  import flash.display.Sprite;
  import flash.display.Stage;
  import flash.events.Event;
  import flash.events.KeyboardEvent;
  import flash.ui.Keyboard;
////////
  public class Ship extends Sprite { 
    private var player:Sprite;
	private var rightArrow:Boolean;
    private var leftArrow:Boolean;
    private var upArrow:Boolean;
    private var downArrow:Boolean;
	private var Go:Number = 5;
	private var Go_di:Number = 0.5*(Math.sqrt(Go*Go+Go*Go));//скорость движения для преодоления гипотенузы равной по длинне Go
////////
    public function Ship() {
      player = createAvatar(0xFFFF00) 
      player.x = 200;
      player.y = 100;
      addChild(player);
      stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressedDown);
	  stage.addEventListener(KeyboardEvent.KEY_UP, keyPressedUp);
	  stage.addEventListener(Event.ENTER_FRAME, moveClip);
}
////////
     private function keyPressedDown(event:KeyboardEvent) {
            if(event.keyCode == Keyboard.RIGHT) {
                rightArrow = true;
            }
            if(event.keyCode == Keyboard.LEFT) {
                leftArrow = true;
            }
            if(event.keyCode == Keyboard.UP) {
                upArrow = true;
            }
            if(event.keyCode == Keyboard.DOWN) {
                downArrow = true;
            }
		}
        private function keyPressedUp(event:KeyboardEvent) {
            if(event.keyCode == Keyboard.RIGHT) {
                rightArrow = false;
            }
            if(event.keyCode == Keyboard.LEFT) {
                leftArrow = false;
            }
            if(event.keyCode == Keyboard.UP) {
                upArrow = false;
            }
            if(event.keyCode == Keyboard.DOWN) {
                downArrow = false;
            }
		}
////////
	    private function moveClip(event:Event) {
            if (rightArrow) {
                player.x += Go;
            }
            if (leftArrow) {
                player.x -= Go;
            }
            if (upArrow) {
                player.y -= Go;
            }
            if (downArrow) {
                player.y += Go;
	        }
	        if (downArrow&&leftArrow) {
                player.y += Go_di-Go;
		        player.x -= Go_di-Go;
	        }
         	if (upArrow&&leftArrow) {
                player.y -= Go_di-Go;
	        	player.x -= Go_di-Go;
	        }
	        if (downArrow&&rightArrow) {
                player.y += Go_di-Go;
	         	player.x += Go_di-Go;
	        }
        	if (upArrow&&rightArrow) {
                player.y -= Go_di-Go;
		        player.x += Go_di-Go;
	        }
        }
////////
    private function createAvatar(bgColor:uint):Sprite {
      var s:Sprite = new Sprite();
      s.graphics.beginFill(bgColor);
      s.graphics.drawCircle(0, 0, 40);
      s.graphics.endFill();
      s.graphics.beginFill(0x000000);
      s.graphics.drawCircle(-15, -10, 5);
      s.graphics.drawCircle(+15, -10, 5);
      s.graphics.endFill();
      s.graphics.lineStyle(2, 0x000000, 100);
      s.graphics.moveTo(-20,15);
      s.graphics.curveTo(0,35, 20,15); 
      return s;
    }
  }
////////
}

Где то так

А вы уверены что не ошиблись разделом ?