html,
body {
  height: 600px;
}

body {
  display: -ms-flexbox;
  display: -webkit-box;
  display: flex;
  -ms-flex-align: center;
  -ms-flex-pack: center;
  -webkit-box-align: center;
  align-items: center;
  -webkit-box-pack: center;
  justify-content: center;
  background-color: #f5f5f5;
}

canvas {
  display: block;
}