html, body {
  padding: 0;
  margin: 0;
  background: #282828;
  width: 100%;
  height: 100%;
  overflow: hidden;
  position: relative;
}
#game {
  width: 100%;
  height: 100%;
  position: absolute;
  left: 50%;
  top: 50%;
  width: 480px;
  height: 480px;
  margin-top: -240px;
  margin-left: -240px;
}
#game canvas {
  display: block;
  /* border: 2px solid red; */
}