:root{--cell-size:40px;--gap:3px;--bg:#171717;--app-bg:#1f1f1f;--cell-bg:#202428;--light-border:#2a323a;--muted-text:#9aa8b9;--text:#e5ecf3;--primary:#60a5ff;--success:#34d399;--danger:#fb7185}*{box-sizing:border-box}body{background:radial-gradient(1200px 400px at 10% 10%, #60a5ff14, transparent), var(--bg);color:var(--text);margin:0;font-family:JetBrains Mono,ui-monospace,SFMono-Regular,Menlo,Monaco,Roboto Mono,Courier New,monospace}.app{text-align:center;-webkit-backdrop-filter:blur(20px);backdrop-filter:blur(20px);background:#ffffff08;border:1px solid #ffffff0d;border-radius:16px;width:min(100%,560px);margin:0 auto;padding:18px}.controls{flex-direction:column;align-items:stretch;gap:10px;margin-bottom:14px;display:flex}button{color:var(--text);cursor:pointer;background:#ffffff05;border:1px solid #ffffff0a;border-radius:10px;width:100%;padding:12px 14px;font-size:1rem;transition:transform .12s,box-shadow .12s,border-color .12s}button:hover,button:focus-visible{border-color:#60a5ff59;transform:translateY(-1px);box-shadow:0 8px 22px #06152899}.sudoku-grid{grid-template-rows:repeat(9, var(--cell-size));gap:var(--gap);width:min(100%, calc(var(--cell-size) * 9 + var(--gap) * 8));background:0 0;margin:12px auto;display:grid}.sudoku-row{grid-template-columns:repeat(9, var(--cell-size));gap:var(--gap);display:grid}.cell{width:var(--cell-size);height:var(--cell-size);text-align:center;font-family:inherit;font-size:1rem;line-height:var(--cell-size);border:1px solid var(--light-border);background:var(--cell-bg);color:var(--text);border-radius:8px;outline:none}.cell:focus{border-color:#60a5ff99;box-shadow:0 0 0 3px #60a5ff1f}.cell-border-right{border-right:3px solid #ffffff29}.cell-border-bottom{border-bottom:3px solid #ffffff29}.cell-initial{color:#061526;background:linear-gradient(#60a5fff2,#60a5ffcc);font-weight:700}.cell-solution{color:#042916;background:linear-gradient(#34d399f2,#22c55ecc);font-weight:700}.cell-unsolved{color:#2b0a0f;background:linear-gradient(#fb7185f2,#f43f5ecc);font-weight:700}.cell-initial.cell-solution{background:linear-gradient(#1e90fff2,#1e90ffd9)}.notes{text-align:left;color:var(--muted-text);margin-top:18px;font-size:.95rem;line-height:1.6}.notes strong{margin-bottom:8px;display:block}.version-footer{color:var(--muted-text);text-align:center;margin-top:14px;font-size:.85rem}@media (width>=640px){:root{--cell-size:44px;--gap:4px}.controls{flex-flow:wrap;justify-content:center}button{width:auto;min-width:130px}}@media (width>=900px){:root{--cell-size:48px;--gap:4px}.app{padding:24px}}