.board-section{padding:40px 5vw}
.board-head{text-align:center;margin-bottom:20px}
.board-head h2{font-size:1.8rem}
.hint{color:var(--mut);font-size:.9rem;max-width:700px;margin:8px auto 0}
.board-wrap{height:min(72vh,720px);border-radius:var(--rad);overflow:hidden;
  background:var(--bg2);border:1px solid var(--line);cursor:crosshair;box-shadow:0 20px 60px rgba(0,0,0,.5)}
#grid{display:block;touch-action:none}
.sel-bar{display:flex;align-items:center;justify-content:center;gap:16px;flex-wrap:wrap;
  margin:18px auto 0;padding:12px 20px;max-width:640px;
  background:var(--card);border:1px solid var(--line);border-radius:14px}
#selInfo{font-weight:600}
@media(max-width:720px){.board-wrap{height:60vh}}