function keyListener(e){
      if(!e){
        //for IE
        e = window.event;
      }
      if(e.keyCode==37 && paddleLeft > 0){
        //keyCode 37 is left arrow
        paddleLeft -= 4;
        paddle.style.left = paddleLeft + 'px';
      }
      if(e.keyCode==39 && paddleLeft < 436){
        //keyCode 39 is right arrow
        paddleLeft += 4;
        paddle.style.left = paddleLeft + 'px';
      }
      //FYI - keyCode 38 is up arrow, keyCode 40 is down arrow
    }