:root { color-scheme: light dark; font-family: system-ui, sans-serif; }
body { margin: 0; padding: 1rem; background: #f4f5f7; color: #172033; }
main { max-width: 34rem; margin: 0 auto; }
.controls { display: flex; flex-wrap: wrap; gap: .4rem; margin: .65rem 0; }
.board { display: grid; grid-template-columns: repeat(4, minmax(3.4rem, 1fr)); gap: .25rem; max-width: 22rem; }
button { min-height: 2.75rem; padding: .35rem .65rem; touch-action: manipulation; }
.cell { position: relative; min-height: 3.5rem; border: 1px solid #64748b; background: #fff; color: #172033; font-size: 1.2rem; }.cell .clue-symbol { position:absolute; top:.1rem; left:.25rem; font-size:.8rem; line-height:1; }.cell .clue-area { position:absolute; inset:0; display:grid; place-items:center; color:#111827; font-size:1.5rem; font-weight:900; line-height:1; text-shadow:0 0 2px #fff; }
.white-piece { background: #fff; }.gray-piece { background: #cbd5e1; }.region-0 { outline: 2px solid #2563eb; outline-offset: -3px; }.region-1 { outline: 2px solid #16a34a; outline-offset: -3px; }.region-2 { outline: 2px solid #d97706; outline-offset: -3px; }.region-3 { outline: 2px solid #db2777; outline-offset: -3px; }.clue { font-weight: 800; }
@media (prefers-color-scheme: dark) { body { background: #111827; color: #e5e7eb; }.cell { color: #172033; } }