.gm-board {
  display: grid; grid-template-columns: repeat(15, 1fr);
  gap: 0; background: #f0c98b; padding: 0;
  border: 3px solid #b9853f; border-radius: 6px;
  width: max-content; margin: 0 auto; max-width: 100%;
  touch-action: none;
}
.gm-cell {
  width: 24px; height: 24px; min-width: 24px; min-height: 24px;
  border-right: 1px solid #c79a5b; border-bottom: 1px solid #c79a5b;
  position: relative; cursor: pointer; display: grid; place-items: center;
}
.gm-cell .stone {
  width: 78%; height: 78%; border-radius: 50%;
  box-shadow: 0 1px 3px rgba(0,0,0,.4);
}
.gm-cell .stone.b { background: radial-gradient(circle at 35% 30%, #555, #000); }
.gm-cell .stone.w { background: radial-gradient(circle at 35% 30%, #fff, #ccc); }
.gm-cell.last::after {
  content: ""; position: absolute; width: 28%; height: 28%;
  border-radius: 50%; border: 2px solid var(--coral); box-sizing: border-box;
}
@media (max-width: 380px) {
  .gm-cell { width: 21px; height: 21px; min-width: 21px; min-height: 21px; }
}