* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  overflow: hidden;
  height: 100%;
  width: 100%;
}

canvas {
  display: block;
  position: fixed; /* use fixed to pin the canvas exactly to viewport */
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}