HTMLify

:root {
  --clr-neutral-100: hsl(0, 0%, 100%);
  --clr-primary-100: hsl(205, 15%, 58%);
  --clr-primary-400: hsl(215, 25%, 27%);
  --clr-primary-800: hsl(217, 33%, 17%);
  --clr-primary-900: hsl(218, 33%, 9%);
}

html {
  color-scheme: dark;
}

body {
  display: grid;
  min-block-size: 100vh;
  place-content: center;
  font-family: system-ui;
  font-size: 1.125rem;
  background-color: var(--clr-primary-800);
}

.scroller {
  max-width: 600px;
}

.scroller__inner {
  padding-block: 1rem;
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin: 0;
  list-style: none;
}

.scroller__inner li {
  padding: 1rem;
  background: var(--clr-primary-400);
  border-radius: 0.5rem;
  box-shadow: 0 0.5rem 1rem -0.25rem var(--clr-primary-900);
}

.scroller[data-animated="true"] {
  overflow: hidden;
  mask: linear-gradient(90deg, transparent, #fff 20%, #fff 80%, transparent);
}

.scroller[data-animated="true"] .scroller__inner {
  width: max-content;
  flex-wrap: nowrap;
  animation: scroll var(--_animation-duration, 40s) var(--_animation-direction, forwards) linear infinite;
}

.scroller[data-speed="fast"] {
  --_animation-duration: 20s;
}

@keyframes scroll {
  to {
    transform: translate(calc(-50% - 0.5rem));
  }
}