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);
}

.grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: clamp(5px, 1.8vw, 10px);
  width: min(150px, 50vw);
  aspect-ratio: 1;
}

.cell {
  display: grid;
  place-items: center;
  border-radius: 12px;
  background: #17141a;
  color: #ffd23f;
  font-weight: 700;
  font-size: clamp(12px, 3.4vw, 16px);
  line-height: 1;
  font-family: inherit;
}

.grid.is-demo .cell {
  animation: wave-loop 2s ease-out infinite;
}

.grid.is-demo .cell:nth-child(1) {
  animation-delay: 0ms;
}

.grid.is-demo .cell:nth-child(2) {
  animation-delay: 70ms;
}

.grid.is-demo .cell:nth-child(3) {
  animation-delay: 140ms;
}

.grid.is-demo .cell:nth-child(4) {
  animation-delay: 70ms;
}

.grid.is-demo .cell:nth-child(5) {
  animation-delay: 140ms;
}

.grid.is-demo .cell:nth-child(6) {
  animation-delay: 210ms;
}

.grid.is-demo .cell:nth-child(7) {
  animation-delay: 140ms;
}

.grid.is-demo .cell:nth-child(8) {
  animation-delay: 210ms;
}

.grid.is-demo .cell:nth-child(9) {
  animation-delay: 280ms;
}

@keyframes wave-loop {
  0%, 6% {
    opacity: 0;
    transform: scale(0.5);
  }
  22%, 62% {
    opacity: 1;
    transform: scale(1);
  }
  84%, 100% {
    opacity: 0;
    transform: scale(0.7);
  }
}
@media (prefers-reduced-motion: reduce) {
  .cell {
    animation: none;
    opacity: 1;
    transform: none;
  }
}