:root{color-scheme:dark;--bg:#0d141b;--panel:#17222b;--ink:#f1eee2;--muted:#b0bfc5;--edge:#42535d;--accent:#bde884;--a:#72dfda;--b:#ffc875;--c:#e7a5ed;font-family:system-ui,-apple-system,"Segoe UI",sans-serif}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font-size:16px;line-height:1.65}a{color:inherit;text-underline-offset:5px}button,select{font:inherit;color:inherit;background:#23333e;border:1px solid var(--edge);border-radius:4px;min-height:44px}button{cursor:pointer;padding:8px 12px}button:hover:not(:disabled){background:#304551}button:disabled{opacity:.45;cursor:default}:focus-visible{outline:3px solid var(--accent);outline-offset:3px}header,footer{max-width:1120px;margin:auto;padding:24px;display:flex;justify-content:space-between;gap:16px;flex-wrap:wrap}header{border-bottom:1px solid var(--edge);font-size:14px}.brand{font-weight:800;letter-spacing:.08em;text-decoration:none}main{max-width:1040px;margin:auto;padding:32px 24px}.eyebrow{font-size:14px;letter-spacing:.12em;color:var(--accent);margin:0 0 16px}.intro{margin-bottom:28px}.intro h1{font:800 clamp(2rem,6vw,3.8rem)/1.06 ui-monospace,monospace;letter-spacing:-.05em;margin:0 0 18px}.intro h1 span{color:var(--accent)}.intro>p:last-child{color:var(--muted);margin:0}.console{display:grid;grid-template-columns:minmax(0,1.3fr) minmax(0,1fr);gap:32px;align-items:start}.play{padding:20px;background:var(--panel);border:1px solid var(--edge);box-shadow:5px 5px 0 #050a0e}.level{display:flex;flex-wrap:wrap;align-items:center;gap:8px}.level label{font-size:14px}.level select{flex:1;min-width:0;width:100%;padding:8px;font-size:16px}.board-meta{display:flex;justify-content:space-between;gap:8px;margin:20px 0 10px;color:var(--muted);font-size:14px}.board{position:relative;aspect-ratio:1;background:#0d171f;border:2px solid #64737c;touch-action:none;user-select:none;-webkit-user-select:none}#cells{position:relative;display:grid;grid-template-columns:repeat(var(--size),1fr);height:100%;z-index:2}.cell{border:0;border-radius:0;border-right:1px solid #30404b;border-bottom:1px solid #30404b;background:transparent;min-height:0;padding:0;position:relative;font:700 clamp(15px,3.5vw,22px)/1 ui-monospace,monospace;display:grid;place-items:center;isolation:isolate}.cell:hover:not(:disabled){background:#ffffff0c}.cell:focus-visible{outline-offset:-4px;z-index:3}.cell .mark{min-width:65%;min-height:65%;display:grid;place-items:center;background:#17222b;border:2px solid currentColor;border-radius:4px;white-space:nowrap}.cell.tip:after{content:'';position:absolute;width:16px;height:16px;border-radius:50%;background:currentColor;z-index:-1}.cell.active-tip:after{outline:3px solid var(--ink);outline-offset:3px}#lines{position:absolute;inset:0;width:100%;height:100%;z-index:1;pointer-events:none}#lines polyline{fill:none;stroke-width:11;stroke-linecap:round;stroke-linejoin:round}.status{min-height:3.5em;margin:16px 0;color:var(--accent);font-size:15px}.status.error{color:#ffc3ad}.actions{display:flex;gap:8px;flex-wrap:wrap}.actions button{font-size:14px;flex:1}.next{background:var(--accent);color:#15221b;width:100%;margin-top:16px;font-weight:800}.next:hover:not(:disabled){background:#d4f2ae}h2{font-size:18px;margin:0 0 8px}.muted,.footnote{color:var(--muted);font-size:14px}.muted{margin:0 0 16px}.path-choice{width:100%;display:flex;align-items:center;gap:12px;text-align:left;margin-bottom:10px;padding:14px;border-left:4px solid var(--path-color)}.path-choice[aria-pressed=true]{outline:2px solid var(--path-color);outline-offset:2px;background:#25343e}.letter{font:700 24px ui-monospace,monospace;color:var(--path-color)}.code{display:block;font:700 20px ui-monospace,monospace;letter-spacing:.18em;overflow-wrap:anywhere}.code .used{color:var(--accent);text-decoration:underline}.path-progress{display:block;font-size:14px;color:var(--muted);margin-top:4px}.rule{border-top:1px solid var(--edge);padding-top:22px;margin-top:24px}ol{padding-left:24px;margin-top:8px}li{margin-bottom:10px}details{border-top:1px solid var(--edge);padding-top:16px}summary{cursor:pointer;font-weight:700;min-height:44px}details p{font-size:14px;color:var(--muted);margin:8px 0 12px}.footnote{margin:28px 0 0}footer{font-size:14px;border-top:1px solid var(--edge);color:var(--muted)}.skip{position:absolute;top:-100px;left:16px;z-index:10;background:var(--bg);padding:10px}.skip:focus{top:8px}[hidden]{display:none!important}@media(max-width:720px){.console{grid-template-columns:1fr;gap:28px}main{padding:24px 16px}.play{padding:12px}.intro h1{font-size:2.6rem}header,footer{padding:18px 16px}}@media(prefers-reduced-motion:no-preference){button,a{transition:background-color .12s}}