.board-hitori {
  display: grid;
  gap: 0;
  width: min(92vw, 28rem);
  aspect-ratio: 1;
  background: var(--board-cell, #fffaf0);
  border: 3px solid var(--board-line-strong, #3b2a1a);
}
.board-hitori .cell {
  display: grid;
  place-items: center;
  font-weight: 700;
  background: var(--board-cell, #fffaf0);
  border: 1px solid var(--board-line);
  color: var(--board-given, #241a14);
}
.board-hitori .cell.is-black {
  background: #241a14;
  color: #fff6e4;
}
.board-hitori .cell.is-white {
  background: var(--board-cell, #fffaf0);
  box-shadow: inset 0 0 0 3px #241a14;
  border-radius: 50%;
}
#board.board-hitori .cell.is-selected {
  box-shadow: inset 0 0 0 2.5px var(--play-ring-active, #19D65A);
  z-index: 2;
}
#board.board-hitori .cell.is-white.is-selected {
  box-shadow: inset 0 0 0 3px #241a14, 0 0 0 2.5px var(--play-ring-active, #19D65A);
}