html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  background: #000;
  overflow: hidden;
}

body {
  display: flex;
  align-items: center;
  justify-content: center;
}

#screen {
  image-rendering: pixelated;
  image-rendering: crisp-edges;
  /* integer-scale to the largest multiple that fits the viewport */
  width: calc(320px * var(--scale, 3));
  height: calc(240px * var(--scale, 3));
}