.xiangqi-board {
  position: relative;
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(10, 1fr);
  aspect-ratio: 9 / 10;
  gap: 2px;
  padding: 8px;
  border: 8px solid #8b4c24;
  border-radius: 8px;
  background: #d9a864;
}
.xiangqi-cell {
  position: relative;
  min-height: 52px;
  border: 1px solid rgba(92,52,24,.62);
  border-radius: 4px;
  background: rgba(255,255,255,.08);
  color: #703019;
  font-size: clamp(18px, 3.2vw, 30px);
  font-weight: 900;
}
.xiangqi-cell.red-piece,
.xiangqi-cell.black-piece {
  background: #f6e7c7;
  border-radius: 50%;
  box-shadow: 0 4px 12px rgba(0,0,0,.22);
}
.xiangqi-cell.red-piece { color: #b2291c; }
.xiangqi-cell.black-piece { color: #24382f; }
.river {
  position: absolute;
  left: 0;
  right: 0;
  top: 48%;
  z-index: 0;
  color: rgba(92,52,24,.7);
  font-size: 30px;
  font-weight: 900;
  text-align: center;
  pointer-events: none;
}
@media (max-width: 640px) {
  .xiangqi-cell { min-height: 38px; }
  .river { font-size: 20px; }
}