/* Keep the original 300 × 250 artwork and scale it as a whole. */
html {
  width: 100%;
  height: auto;
  min-height: 100%;
}

body {
  width: 100%;
  max-width: 400px;
  height: auto;
  aspect-ratio: 6 / 5;
  position: relative;
}

.banner {
  position: absolute;
  top: 0;
  left: 0;
  transform-origin: top left;
  transform: scale(var(--banner-scale, 1));
}