/* Number Shuffle - classic 15 puzzle sliding tiles. */
.s15-arena { display: flex; flex-direction: column; align-items: center; gap: 12px; }

.s15-board {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 6px;
  padding: 10px;
  width: min(90vw, 340px);
  aspect-ratio: 1 / 1;
  background: var(--casino-carbon, #12121e);
  border: 1px solid var(--casino-line, #2e2e44);
  border-radius: 14px;
  touch-action: manipulation;
  user-select: none;
}

.s15-tile {
  display: flex;
  align-items: center;
  justify-content: center;
  border: none;
  border-radius: 10px;
  background: #4a4a68;
  color: #f5f6fa;
  font-family: "Chivo", system-ui, sans-serif;
  font-weight: 800;
  font-size: clamp(18px, 5.5vw, 28px);
  cursor: pointer;
  transition: transform .1s ease, background .15s ease;
}
.s15-tile:active { transform: scale(.92); }
.s15-tile.ok { background: #7c5cff; }
.s15-tile.blank { background: transparent; cursor: default; }