html,
body {
  height: 100%;
  min-height: 100%;
  margin: 0;
  padding: 0;
}
canvas {
  background-color: #111;
  display: block;
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  padding: 0;
  margin: auto;
}