.sk-board {
  display: grid; gap: 2px; width: min(94vw, 440px); aspect-ratio: 1; margin: 0 auto;
  background: var(--line); padding: 2px; border-radius: 12px;
}
.sk-cell {
  position: relative; background: var(--surface); border-radius: 4px;
  display: grid; place-items: center; cursor: pointer; font-weight: 900; font-size: clamp(16px, 5vw, 26px);
  color: var(--ink); user-select: none;
}
.sk-cell .num {
  width: 30px; height: 30px; display: grid; place-items: center;
  border-radius: 50%; background: rgba(255,255,255,.75); box-shadow: var(--shadow-sm);
}
.sk-cell.sel { outline: 3px solid var(--grape); outline-offset: -3px; z-index: 2; }
.sk-cell.locked { color: rgba(0,0,0,.55); }