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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.tl {
  position: relative;
  width: min(300px, 88vw);
  padding-left: 24px;
}

.tl__track {
  position: absolute;
  left: 5px;
  top: 4px;
  bottom: 4px;
  width: 2px;
  background: rgba(23, 20, 26, 0.16);
  border-radius: 999px;
  overflow: hidden;
}

.tl__fill {
  position: absolute;
  inset: 0;
  transform: scaleY(0.25);
  transform-origin: top;
  background: #17141a;
  transition: transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.tl__list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.tl__stop {
  display: flex;
  align-items: center;
  gap: 12px;
  background: none;
  border: 0;
  padding: 0;
  text-align: left;
  cursor: pointer;
  font: inherit;
  color: rgba(23, 20, 26, 0.72);
  -webkit-tap-highlight-color: transparent;
}

.tl__dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: rgba(23, 20, 26, 0.3);
  flex: 0 0 auto;
  position: relative;
  transition: background 300ms cubic-bezier(0.2, 0.8, 0.2, 1), transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
}

.tl__time {
  font-weight: 700;
  font-size: clamp(11px, 3vw, 12px);
  line-height: 1;
  font-family: inherit;
  flex: 0 0 auto;
}

.tl__label {
  font-weight: 600;
  font-size: clamp(12px, 3.4vw, 13px);
  line-height: 1.3;
  font-family: inherit;
}

.tl__stop[aria-current=step] {
  color: #17141a;
}

.tl__stop[aria-current=step] .tl__dot {
  background: #17141a;
  transform: scale(1.3);
  box-shadow: 0 0 0 4px rgba(23, 20, 26, 0.14);
}

.tl.is-demo .tl__fill {
  animation: tl-fill 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

@keyframes tl-fill {
  0%, 8% {
    transform: scaleY(0.25);
  }
  25%, 33% {
    transform: scaleY(0.5);
  }
  50%, 58% {
    transform: scaleY(0.75);
  }
  75%, 83% {
    transform: scaleY(1);
  }
  100% {
    transform: scaleY(0.25);
  }
}
.tl.is-demo li:nth-child(1) .tl__dot {
  animation: tl-pulse 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

.tl.is-demo li:nth-child(2) .tl__dot {
  animation: tl-pulse 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: 0.5s;
}

.tl.is-demo li:nth-child(3) .tl__dot {
  animation: tl-pulse 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: 1s;
}

.tl.is-demo li:nth-child(4) .tl__dot {
  animation: tl-pulse 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
  animation-delay: 1.5s;
}

@keyframes tl-pulse {
  0%, 92%, 100% {
    background: rgba(23, 20, 26, 0.3);
    transform: scale(1);
    box-shadow: 0 0 0 0 rgba(23, 20, 26, 0);
  }
  4% {
    background: #17141a;
    transform: scale(1.3);
    box-shadow: 0 0 0 4px rgba(23, 20, 26, 0.14);
  }
  20% {
    background: #17141a;
    transform: scale(1.3);
    box-shadow: 0 0 0 4px rgba(23, 20, 26, 0.14);
  }
}
@media (prefers-reduced-motion: reduce) {
  .tl__fill, .tl__dot {
    transition: none;
  }
  .tl.is-demo .tl__fill,
  .tl.is-demo .tl__stop .tl__dot {
    animation: none !important;
  }
}