:root{--bg: #0b1220;--panel: #121d2f;--line: #2a3c56;--ink: #e2e9f4;--dim: #90a2bd;--accent: #f2b880;--road: #4cc9f0;--good: #6fd3a8;--bad: #f87171;--border: #93a9c4;--cell: 46px}*{box-sizing:border-box}body{margin:0;background:radial-gradient(1200px 600px at 50% -10%,#16273f 0%,var(--bg) 60%);color:var(--ink);font-family:ui-sans-serif,system-ui,-apple-system,Helvetica Neue,sans-serif;line-height:1.65}main{max-width:880px;margin:0 auto;padding:2.2rem 1.2rem 4rem}header h1{font-size:2.1rem;margin:0 0 .5rem;letter-spacing:-.02em}header h1 span{color:var(--road)}.sub{color:var(--dim);margin:0 0 1.4rem;font-size:.95rem}.sub strong{color:var(--ink)}.sub em{color:var(--accent);font-style:italic}#wrap{display:flex;justify-content:center}#stage{position:relative;padding:10px;background:var(--panel);border:1px solid var(--line);border-radius:12px}#board{display:grid;gap:0;position:relative}#lines{position:absolute;left:10px;top:10px;pointer-events:none}#lines line{stroke:var(--road);stroke-width:7;stroke-linecap:round}.cell{width:var(--cell);height:var(--cell);position:relative;display:flex;align-items:flex-start;justify-content:flex-start;padding:1px 4px;font-variant-numeric:tabular-nums;font-size:.8rem;font-weight:600;text-shadow:0 0 3px #0b1220,0 0 6px #0b1220;color:var(--accent);background:#0f1a2b;border:1px solid #1d2b41;-webkit-user-select:none;user-select:none;touch-action:none}.cell.wall-t{border-top:3px solid var(--border)}.cell.wall-b{border-bottom:3px solid var(--border)}.cell.wall-l{border-left:3px solid var(--border)}.cell.wall-r{border-right:3px solid var(--border)}.cell.edge-t{border-top:3px solid #47607f}.cell.edge-b{border-bottom:3px solid #47607f}.cell.edge-l{border-left:3px solid #47607f}.cell.edge-r{border-right:3px solid #47607f}.cell.off:after{content:"";position:absolute;left:50%;top:50%;transform:translate(-50%,-50%);width:12px;height:12px;background:linear-gradient(45deg,transparent 44%,var(--dim) 44%,var(--dim) 56%,transparent 56%),linear-gradient(-45deg,transparent 44%,var(--dim) 44%,var(--dim) 56%,transparent 56%);opacity:.85}.cell.onroad:after{content:"";position:absolute;left:50%;top:50%;transform:translate(-50%,-50%);width:7px;height:7px;border-radius:50%;background:var(--road);opacity:.6}.cell.flash{animation:flash .7s ease-out}@keyframes flash{0%{background:#2a5f7a}to{background:#0f1a2b}}.hud{text-align:center;min-height:1.6rem;margin:.9rem 0 .2rem;color:var(--dim);font-size:.9rem}.hud .win{color:var(--good)}.hud .err{color:var(--bad)}.controls{display:flex;flex-wrap:wrap;gap:.6rem;align-items:center;justify-content:center;margin:.8rem 0 1.6rem}label{color:var(--dim);font-size:.85rem}select,button{font:inherit;font-size:.85rem;color:var(--ink);background:var(--panel);border:1px solid var(--line);border-radius:8px;padding:.35rem .7rem;cursor:pointer}button:hover,select:hover{border-color:var(--road)}.notes h2{font-size:1.05rem;margin:2rem 0 .5rem;color:var(--accent)}.notes p{color:var(--dim);font-size:.92rem}.notes strong{color:var(--ink)}.notes code{background:#16233a;border-radius:4px;padding:0 .3em;color:var(--road)}footer{margin-top:2.4rem;border-top:1px solid var(--line);padding-top:1rem;color:var(--dim);font-size:.82rem}@media (max-width: 620px){:root{--cell: 34px}}