body {
  height: 100vh;
  margin: 0;
  display: grid;
  place-items: center;
  overflow: hidden;
}

main {
  transform-style: preserve-3d;
  perspective: 80vmin;
}

section {
  width: 100vmin;
  aspect-ratio: 4 / 3;
  outline: 2px dashed red;
  transform-origin: 100% 50%;
  rotate: y 40deg;
  container-type: inline-size;
  mask: linear-gradient(90deg, #0000 0 40px, #fff, #0000 calc(100% - 40px) 100%);
  position: relative;
}

section div {
  width: 40px;
  aspect-ratio: 1;
  background: red;
  position: absolute;
  top: calc(var(--y) * 1%);
  background: hsl(var(--hue), 90%, 60%);
  animation-name: travel;
  animation-iteration-count: infinite;
  animation-delay: calc(var(--d) * -1s);
  animation-duration: calc(var(--a) * 1s);
}

@keyframes travel {
  0% {
    translate: 100cqi 0;
  }
  100% {
    translate: -50% 0;
  }
}