:root {
  --bg: #0f1115;
  --panel: #1a1b1f;
  --tile: #1f2433;
  --accent: #ff9300;
  --text: #e7ecf3;
  --muted: #9aa5b1;
  --grid: #2a2c31;
  --glow: rgba(255, 147, 0, 0.22);
}

* {
  box-sizing: border-box;
}

html,
body {
  height: 100%;
}

body {
  margin: 0;
  font-family: "Space Grotesk", "Noto Sans JP", system-ui, sans-serif;
  background:
    radial-gradient(900px 500px at 80% -10%, rgba(255, 147, 0, 0.2), transparent 55%),
    radial-gradient(700px 400px at 0% 20%, rgba(255, 147, 0, 0.15), transparent 60%),
    linear-gradient(180deg, #0e0f12 0%, #0f1115 100%);
  color: var(--text);
  min-height: 100svh;
  display: block;
  overflow: hidden;
  overscroll-behavior: none;
  touch-action: none;
}

.wrap {
  width: min(88vw, 480px);
  display: grid;
  gap: 14px;
  position: fixed;
  inset: 0;
  margin: auto;
  height: fit-content;
}

.top {
  display: grid;
  grid-template-columns: 1fr auto auto auto;
  gap: 12px;
  align-items: center;
}

h1 {
  margin: 0;
  font-size: 30px;
  letter-spacing: 0.04em;
}

.subtitle {
  margin: 6px 0 0;
  color: var(--muted);
  font-size: 11px;
}

.scorebox {
  background: var(--panel);
  border: 1px solid #2b2c31;
  padding: 8px 12px;
  border-radius: 10px;
  min-width: 72px;
  text-align: center;
  box-shadow: 0 0 0 1px rgba(255, 147, 0, 0.05);
}

.scorebox .label {
  color: var(--muted);
  font-size: 10px;
  letter-spacing: 0.08em;
}

.scorebox .value {
  font-size: 16px;
  font-weight: 700;
}

.btn {
  background: var(--accent);
  color: #1a1a1a;
  border: none;
  padding: 10px 14px;
  border-radius: 10px;
  cursor: pointer;
  font-weight: 600;
  box-shadow: 0 8px 18px rgba(255, 147, 0, 0.25);
}

.btn:hover {
  filter: brightness(1.05);
}

.btn-secondary {
  background: #1f232b;
  color: var(--text);
  border: 1px solid #2c2d33;
  box-shadow: none;
}

.btn-share {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 12px;
}

.share-icon {
  width: 14px;
  height: 14px;
  display: block;
}

.mode {
  display: inline-flex;
  gap: 8px;
}

.btn-toggle {
  background: #23293a;
  color: var(--text);
  border: 1px solid #2f374a;
  box-shadow: none;
}

.btn-toggle.active {
  background: var(--accent);
  color: #1a1a1a;
  border-color: transparent;
}

.board {
  position: relative;
  background: var(--panel);
  border-radius: 18px;
  padding: 10px;
  border: 1px solid #2c2d33;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.35), 0 0 0 1px var(--glow);
  touch-action: none;
}

.grid {
  --gap: 8px;
  --cell: 0px;
  aspect-ratio: 1 / 1;
  width: 100%;
  position: relative;
}

.grid-bg {
  display: grid;
  gap: var(--gap);
  grid-template-columns: repeat(4, var(--cell));
  grid-template-rows: repeat(4, var(--cell));
  width: 100%;
  height: 100%;
  place-content: center;
}

.tile-layer {
  position: absolute;
  inset: 0;
  pointer-events: none;
}

.cell {
  background: var(--grid);
  border-radius: 12px;
  width: 100%;
  height: 100%;
  box-shadow: inset 0 0 0 1px rgba(255, 147, 0, 0.08);
}

.tile {
  position: absolute;
  width: var(--cell);
  height: var(--cell);
  display: grid;
  place-items: center;
  font-size: 28px;
  font-weight: 800;
  border-radius: 12px;
  transform: translate(
      calc(var(--col) * (var(--cell) + var(--gap))),
      calc(var(--row) * (var(--cell) + var(--gap)))
    );
  transition: transform 140ms ease;
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
}

.tile.spawn {
  animation: pop 160ms ease;
}

@keyframes pop {
  0% {
    transform: translate(
        calc(var(--col) * (var(--cell) + var(--gap))),
        calc(var(--row) * (var(--cell) + var(--gap)))
      )
      scale(0.75);
  }
  100% {
    transform: translate(
      calc(var(--col) * (var(--cell) + var(--gap))),
      calc(var(--row) * (var(--cell) + var(--gap)))
    );
  }
}

.overlay {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  background: rgba(8, 10, 14, 0.7);
  backdrop-filter: blur(2px);
  border-radius: 18px;
}

.overlay.hidden {
  display: none;
}

.overlay-card {
  background: #121826;
  border: 1px solid #2b3448;
  border-radius: 16px;
  padding: 20px;
  text-align: center;
  display: grid;
  gap: 12px;
}

.legend {
  color: var(--muted);
  text-align: center;
  font-size: 12px;
  display: grid;
  gap: 6px;
}

.credit {
  color: #c7a97a;
  font-size: 11px;
}

.version {
  color: #6f7782;
  font-size: 10px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

@media (max-width: 520px) {
  .top {
    grid-template-columns: 1fr 1fr;
    grid-auto-rows: auto;
  }

  .top .btn {
    grid-column: 1 / -1;
  }
}