:root {
  --bg-a: #eef7fb;
  --bg-b: #d9e8f3;
  --ink: #1a2430;
  --muted: #536172;
  --panel: #ffffffcc;
  --border: #0f172a1e;

  --u: #f8f8f5;
  --d: #ffd54a;
  --f: #29aa62;
  --b: #2f65e5;
  --r: #f24d45;
  --l: #ff9527;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "Space Grotesk", ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif;
  color: var(--ink);
  background:
    radial-gradient(circle at 15% 12%, #ffffffb0, #ffffff00 35%),
    radial-gradient(circle at 85% 0%, #abd8ef88, #abd8ef00 38%),
    linear-gradient(155deg, var(--bg-a), var(--bg-b));
}

.app {
  width: min(1200px, 100% - 1.6rem);
  margin: 1rem auto;
  display: grid;
  grid-template-columns: 320px 1fr;
  gap: 1rem;
}

.panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 16px;
  box-shadow: 0 14px 34px #0f172a17;
}

.sidebar {
  padding: 1rem;
  display: grid;
  gap: 0.95rem;
  align-content: start;
}

h1,
h2,
p {
  margin: 0;
}

h1 {
  font-size: 1.52rem;
}

h2 {
  font-size: 1.1rem;
}

.hint {
  color: var(--muted);
}

.label {
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-size: 0.78rem;
  color: #35607c;
  margin-bottom: 0.35rem;
}

.controls {
  display: grid;
  gap: 0.5rem;
  padding: 0.72rem;
  border-radius: 12px;
  background: #f8fbff;
  border: 1px solid #d8e5ef;
}

.btn-group {
  display: flex;
  flex-wrap: wrap;
  gap: 0.42rem;
}

.turn-mode {
  display: grid;
  width: 100%;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.42rem;
}

.moves-grid {
  display: grid;
  width: 100%;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.5rem;
}

.moves-grid .btn {
  width: 100%;
  min-height: 54px;
  padding: 0.35rem 0.35rem;
  font-weight: 700;
  font-size: 1.05rem;
}

.btn-group.actions {
  display: grid;
  width: 100%;
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.btn {
  font: inherit;
  border: 0;
  border-radius: 999px;
  padding: 0.47rem 0.72rem;
  min-height: 42px;
  cursor: pointer;
  background: #e7f5fb;
  color: var(--ink);
  transition: transform 120ms ease, background-color 120ms ease;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn.action {
  background: #f3eee3;
}

.btn.action:hover {
  background: #eadfc9;
}

.mode-btn {
  min-height: 44px;
  background: #eaf0f6;
  font-weight: 600;
}

.mode-btn.is-active {
  background: #35607c;
  color: #fff;
}

.status {
  min-height: 1.2rem;
  color: var(--muted);
  font-size: 0.92rem;
}

.legend {
  display: grid;
  gap: 0.36rem;
  padding: 0.72rem;
  border-radius: 12px;
  border: 1px solid #d8e5ef;
  background: #f8fbff;
  color: #32475b;
  font-size: 0.92rem;
}

.viewer {
  padding: 0.9rem;
  display: grid;
  grid-template-rows: auto 1fr;
  gap: 0.65rem;
  min-height: 720px;
}

.viewer-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
}

.viewer-head p {
  color: var(--muted);
  font-size: 0.9rem;
}

.stage {
  --cube-size: min(54vmin, 320px);
  position: relative;
  display: grid;
  place-items: center;
  border-radius: 14px;
  min-height: 620px;
  overflow: hidden;
  background:
    radial-gradient(circle at 50% 35%, #ffffff, #edf3f9 48%, #e2ebf5 100%);
  perspective: 900px;
  perspective-origin: 50% 45%;
  touch-action: none;
  user-select: none;
}

.stage::after {
  content: "";
  position: absolute;
  width: calc(var(--cube-size) * 0.92);
  height: 22px;
  border-radius: 999px;
  background: #0f172a28;
  filter: blur(10px);
  transform: translateY(calc(var(--cube-size) * 0.38));
}

.cube {
  width: var(--cube-size);
  height: var(--cube-size);
  position: relative;
  transform-style: preserve-3d;
  transform: rotateX(-28deg) rotateY(-38deg);
  animation: idle-spin 18s linear infinite;
  cursor: grab;
  z-index: 2;
  will-change: transform;
}

.cube.interacted {
  animation: none;
}

.cube.is-dragging {
  cursor: grabbing;
}

.face {
  position: absolute;
  inset: 0;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  gap: 0.2rem;
  padding: 0.26rem;
  border-radius: 10px;
  background: #111827;
  box-shadow: inset 0 0 0 1px #ffffff14;
  backface-visibility: hidden;
}

.face-u {
  transform: rotateX(90deg) translateZ(calc(var(--cube-size) / 2));
  filter: brightness(1.08);
}

.face-d {
  transform: rotateX(-90deg) translateZ(calc(var(--cube-size) / 2));
  filter: brightness(0.72);
}

.face-f {
  transform: translateZ(calc(var(--cube-size) / 2));
  filter: brightness(1.02);
}

.face-b {
  transform: rotateY(180deg) translateZ(calc(var(--cube-size) / 2));
  filter: brightness(0.78);
}

.face-l {
  transform: rotateY(-90deg) translateZ(calc(var(--cube-size) / 2));
  filter: brightness(0.88);
}

.face-r {
  transform: rotateY(90deg) translateZ(calc(var(--cube-size) / 2));
  filter: brightness(0.93);
}

.sticker {
  border-radius: 3px;
  box-shadow:
    inset 0 0 0 1px #0f172a2c,
    0 1px 2px #00000026;
}

@keyframes idle-spin {
  from {
    transform: rotateX(-28deg) rotateY(-38deg);
  }
  to {
    transform: rotateX(-28deg) rotateY(322deg);
  }
}

@media (max-width: 980px) {
  .app {
    width: min(100%, calc(100% - 1rem));
    margin: 0.55rem auto;
    grid-template-columns: 1fr;
    gap: 0.7rem;
  }

  .sidebar {
    padding: 0.82rem;
    gap: 0.64rem;
  }

  .controls,
  .legend {
    padding: 0.52rem;
  }

  .controls .label {
    margin-bottom: 0.2rem;
    font-size: 0.72rem;
  }

  .label-turn,
  .label-moves,
  .turn-mode,
  #move-buttons {
    display: none;
  }

  .moves-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }

  .btn {
    min-height: 42px;
  }

  .mode-btn {
    min-height: 40px;
  }

  .moves-grid .btn {
    min-height: 50px;
    font-size: 1.06rem;
  }

  .viewer {
    padding: 0.72rem;
    min-height: 480px;
  }

  .viewer-head {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.2rem;
  }

  .stage {
    --cube-size: min(58vmin, 255px);
    min-height: 380px;
  }
}

@media (hover: none) {
  .btn:hover {
    transform: none;
  }
}