This should be simple...but it doesn't work

1

I made a simple little program to move a movieclip around, but it doesn’t work, and for the life of me I can’t seem to figure out why. It’s so simple! The program runs with no errors but the movieclip won’t move. I put in a trace statement that doesn’t return anything, so it’s gotta be something the matter with my event listener.

package  {
    
    import flash.display.MovieClip;
    import flash.display.Stage;
 
    //our Engine class it extends MovieClip
    public class Engine extends MovieClip
    {
        //our constructor function. This runs when an object of 
        //the class is created
        public function Engine() 
        {
            //create an object of our ship from the Ship class
            var ourShip:Ship = new Ship();
            //add it to the display list
            stage.addChild(ourShip);
 
            ourShip.x = stage.stageWidth / 2;
            ourShip.y = stage.stageHeight / 2;
        }
 
    }
 
}

package 
{

    import flash.display.MovieClip;
    import flash.ui.Keyboard;
    import flash.events.*;

    public class Ship extends MovieClip
    {

        
        public function Ship()
        {
            addEventListener(KeyboardEvent.KEY_DOWN, loop);
        }

        private function loop(event:KeyboardEvent):void
        {
            if (event.keyCode == Keyboard.LEFT)
            {
                this.x -=  2;
            }
            else if (event.keyCode == Keyboard.RIGHT)
            {
                this.x +=  2;
            }
            else if (event.keyCode == Keyboard.UP)
            {
                this.y -=  2;
            }
            else if (event.keyCode == Keyboard.DOWN)
            {
                this.y +=  2;
            }
        trace (event.keyCode);
        }

    }

}