/* ===== 手番方向ハイライト ===== */

.board {
  position: relative;
}

/* 共通スタイル */
.board::before {
  content: "";
  position: absolute;
  pointer-events: none;
}

/* P1（上が手前） */
.board.turn0::before {
  top: -10px;
  left: 0;
  right: 0;
  height: 10px;
  background: linear-gradient(to bottom, rgba(0,120,255,1), transparent);
}

/* P2（右が手前） */
.board.turn1::before {
  right: -10px;
  top: 0;
  bottom: 0;
  width: 10px;
  background: linear-gradient(to left, rgba(0,120,255,1), transparent);
}

/* P3（下が手前） */
.board.turn2::before {
  bottom: -10px;
  left: 0;
  right: 0;
  height: 10px;
  background: linear-gradient(to top, rgba(0,120,255,1), transparent);
}

/* P4（左が手前） */
.board.turn3::before {
  left: -10px;
  top: 0;
  bottom: 0;
  width: 10px;
  background: linear-gradient(to right, rgba(0,120,255,1), transparent);
}