html, body {
  margin: 0;
  padding: 0;
  background-color: powderblue;
}

canvas {
  display: block;
  margin: auto;

  margin: 0;
  position: absolute;
  top: 50%;
  left: 50%;
  -ms-transform: translateY(-50%, -50%);
  transform: translate(-50%, -50%);
}