html,
body {
  height: 100%;
}

body {
  background: black;
  margin: 0;
  display: grid;
  place-items: center;
}

canvas {
  outline: 1px solid white;
  max-width: 100%;
  max-height: 100%;
  /*
  set aspect-ratio to canvas width/height
  */
  aspect-ratio: 640/480;
}