.ttt-board {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
  width: min(380px, 100%);
}

.ttt-cell {
  aspect-ratio: 1;
  border: 1px solid var(--hairline-strong);
  border-radius: var(--radius-md);
  background: var(--canvas);
  box-shadow: var(--shadow-sm);
  color: var(--ink);
  font-size: clamp(34px, 8vw, 52px);
  font-weight: 600;
  line-height: 1;
  cursor: pointer;
  transition:
    transform 140ms ease,
    border-color 140ms ease,
    box-shadow 140ms ease;
}

.ttt-cell:hover,
.ttt-cell:focus-visible {
  transform: translateY(-1px);
  border-color: var(--ink);
  box-shadow: var(--shadow-md);
}

.ttt-cell.is-x {
  color: var(--primary-deep);
}

.ttt-cell.is-o {
  color: #2563eb;
}

.ttt-cell.is-win {
  border-color: var(--primary);
  background: rgba(62, 207, 142, 0.12);
}