#game-board {
  display: grid;
  grid-template-columns: repeat(3, 100px);
  grid-template-rows: repeat(3, 100px);
  gap: 4px;
}

.cell {
  border: 2px solid #333;
  background: #fff;
  cursor: pointer;
  font-size: 2.5rem;
  font-family: sans-serif;
  display: flex;
  align-items: center;
  justify-content: center;
  user-select: none;
  box-sizing: border-box;
}

.cell:hover {
  background: #f0f0f0;
}