:root {
  --tile-h: 100vh;
  --duration: 2s;
}

html, body {
  height: 100%;
  margin: 0;
}

#scroll {
  height: 100vh;
  width: 100vw;
  overflow: hidden;

  background-repeat: repeat-y;
  background-size: 100vw auto;
  background-position: 0 0;

  animation: scrollUp var(--duration) linear infinite;
}

@keyframes scrollUp {
  from { background-position: 0 0; }
  to   { background-position: 0 calc(-1 * var(--tile-h)); }
}