:root {--cage-line:#475569;} :root[data-theme=dark] {--cage-line:#cbd5e1;}
@media(prefers-color-scheme:dark) {:root:not([data-theme=light]) {--cage-line:#cbd5e1;}}
#board {grid-template-columns:repeat(4,minmax(0,1fr));gap:0;} .cell {position:relative;display:grid;place-items:center;border-radius:0;border-color:var(--cage-line);padding:14px 0 0;font-size:1.65rem;}
.cage-label {position:absolute;left:4px;top:3px;font-size:.72rem;font-weight:700;line-height:1;letter-spacing:0;color:var(--text);}
.cell.invalid {box-shadow:inset 0 0 0 2px var(--error);} .cell.selected {outline:3px solid #2563eb;outline-offset:-4px;} .cell:disabled {opacity:1;}
@media(max-width:360px) {main {width:calc(100% - 16px);} .cell {font-size:1.45rem;} .cage-label {font-size:.68rem;}}