居中画布元素而不影响游戏坐标

.element {
  position: absolute;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);
}

var canvas = document.getElementById("myCanvas");
var element = document.getElementById("myElement");

var canvasWidth = canvas.width;
var canvasHeight = canvas.height;
var elementWidth = element.offsetWidth;
var elementHeight = element.offsetHeight;

var x = (canvasWidth - elementWidth) / 2;
var y = (canvasHeight - elementHeight) / 2;

element.style.left = x + "px";
element.style.top = y + "px";