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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.nav {
  position: relative;
  display: flex;
  gap: 16px;
}

.tab {
  flex: 0 0 auto;
  width: 96px;
  height: 32px;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.1);
}

.indicator {
  position: absolute;
  left: 0;
  bottom: -8px;
  width: 96px;
  height: 3px;
  border-radius: 4px;
  background: linear-gradient(90deg, transparent, #2df5c0, transparent);
  box-shadow: 0 0 12px #2df5c0, 0 0 24px rgba(45, 245, 192, 0.6);
}

.stage.is-demo .indicator {
  animation: slide 2s cubic-bezier(0.2, 0.8, 0.2, 1) infinite;
}

@keyframes slide {
  0%, 40% {
    transform: translateX(0);
  }
  60%, 90% {
    transform: translateX(112px);
  }
  100% {
    transform: translateX(0);
  }
}
@media (prefers-reduced-motion: reduce) {
  .stage.is-demo .indicator {
    animation: none;
  }
}