html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffffff;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.rail {
  position: fixed;
  top: 0;
  right: 0;
  width: 4px;
  height: 100%;
  background: rgba(23, 20, 26, 0.1);
}

.rail__fill {
  width: 100%;
  height: 100%;
  background: #2f6df6;
  transform: scaleY(0);
  transform-origin: top;
}
@supports (animation-timeline: scroll()) {
  .rail__fill {
    animation: fill-y linear both;
    animation-timeline: scroll(root);
  }
}

@keyframes fill-y {
  to {
    transform: scaleY(1);
  }
}
.rail__fill.is-demo {
  animation: fill-y-loop 2s linear infinite;
}

@keyframes fill-y-loop {
  0% {
    transform: scaleY(0);
  }
  92% {
    transform: scaleY(1);
  }
  100% {
    transform: scaleY(1);
  }
}
.page {
  padding: 40px 32px 0 24px;
}

.page__block {
  height: 24px;
  margin: 0 0 16px;
  border-radius: 8px;
  background: rgba(23, 20, 26, 0.08);
}
.page__block.short {
  width: 55%;
}

@media (prefers-reduced-motion: reduce) {
  .rail__fill, .rail__fill.is-demo {
    animation: none !important;
    transform: scaleY(1);
  }
}