.board {
  display: grid;
  grid-template-columns: repeat(9, 32px);
  grid-template-rows: repeat(9, 32px);
  gap: 0;
  border: 2px solid black;
  background-color: #cea;

  > .cell {
    display: flex;
    align-items: center;
    justify-content: center;
    border-width: 0.5px;
    border-style: solid;
    border-color: black;
    font-size: 16px;
  }

  /* every 3rd column thicker */
  > .cell:nth-child(3n) {
    border-right-width: 2px;
    border-right-color: black;
  }

  /* 3rd & 6th rows thicker */
  > .cell:nth-child(n+19):nth-child(-n+27),
  > .cell:nth-child(n+46):nth-child(-n+54) {
    border-bottom-width: 2px;
    border-bottom-color: black;
  }
}