Перемещение квадрата стрелачками на клавиатуре не работает в чем причина не могу понять

const arrClass = ["red", "green", "yellow", "blue"];

const foo = (el) => {
  const i = (arrClass.indexOf(el.className) + 1) % arrClass.length
  el.className = arrClass[i];
}

window.addEventListener("keydown", function moveRect(e) {
  var rect = document.getElementById("block");

  var cs = getComputedStyle(rect);

  var left = parseInt(cs.marginLeft);
  var top = parseInt(cs.marginTop);
  switch (e.keyCode) {
    case 37: //влево
      rect.style.marginLeft = left - 10 + "px";
      break;
    case 38: //вверх
      rect.style.marginTop = top - 10 + "px";
      break;
    case 39: //вправо
      rect.style.marginLeft = left + 10 + "px";
      break;
    case 40: //вниз
      rect.style.marginTop = top + 10 + "px";
      break;
    case 32: //SPACE
      rect.style.backgroundColor = "blue";
      break;
    case 13: //ENTER
      rect.style.display = "block";
      break;
    case 27: //ESC
      rect.style.display = "none";
      break;
  }
})

#block {
  width: 10px;
  height: 10px;
  background: green;
}
.red {
  width: 50px;
  height: 50px;
  display: inline-block;
  margin-left: 15px;
  background: red;
}

.green {
  width: 50px;
  height: 50px;
  display: inline-block;
  margin-left: 15px;
  background: green;
}

.yellow {
  width: 50px;
  height: 50px;
  display: inline-block;
  margin-left: 15px;
  background: yellow;
}

.blue {
  width: 50px;
  height: 50px;
  display: inline-block;
  margin-left: 15px;
  background: blue;
}

<div class="red" onclick="foo(this)">
  <div id="block"></div>

</div>