.ut-board {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 6px;
  width: min(360px, 92vw);
  margin: 0 auto;
}
.ut-mini {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2px;
  padding: 4px;
  background: #e2e8f0;
  border-radius: 8px;
  border: 2px solid transparent;
}
.ut-mini.active { border-color: #2563eb; background: #dbeafe; }
.ut-mini.done { opacity: .55; }
.ut-cell {
  aspect-ratio: 1 / 1;
  display: flex; align-items: center; justify-content: center;
  font-size: clamp(14px, 4.5vw, 20px);
  font-weight: 800;
  background: #fff; border-radius: 4px; cursor: pointer; user-select: none;
  color: #334155;
}
.ut-cell.x { color: #ef4444; }
.ut-cell.o { color: #2563eb; }
.ut-mini.winx { background: #fee2e2; }
.ut-mini.wino { background: #dbeafe; }