:root { --bg:#0b0d12; --card:#141922; --ink:#e7ecf3; --muted:#9fb0c4; --accent:#3aa3ff; --error:#ff4d6d; }
* { box-sizing: border-box; }
body { margin:0; font-family: ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,Inter,Arial; color:var(--ink); background:linear-gradient(180deg,#0a0d13, #0e131b); min-height:100dvh; display:flex; flex-direction:column; gap:16px; }
header { display:flex; align-items:center; justify-content:space-between; padding:16px; max-width:900px; margin:0 auto; width:100%; }
h1 { font-size:24px; margin:0; letter-spacing:.5px; }
.controls { display:flex; gap:8px; flex-wrap:wrap; }
button, select { background:var(--card); color:var(--ink); border:1px solid #243041; border-radius:10px; padding:8px 12px; cursor:pointer; }
button:hover, select:hover { border-color:var(--accent); }
main { display:grid; place-items:center; padding:8px 16px 24px; }
.board { display:grid; grid-template-columns: repeat(9, 48px); gap:2px; background:#243041; padding:6px; border-radius:16px; box-shadow: 0 10px 30px rgba(0,0,0,.35); }
.cell { width:48px; height:48px; display:grid; place-items:center; background:var(--card); border:1px solid #1d2735; font-size:20px; font-weight:600; border-radius:8px; }
.cell input { width:100%; height:100%; text-align:center; border:none; background:transparent; color:var(--ink); font: inherit; outline:none; caret-color:var(--accent); }
.cell.prefilled input { color:#8eb6ff; }
.cell.conflict { background: rgba(255,77,109,.1); border-color:var(--error); }
.cell.focused { outline:2px solid var(--accent); }
.cell.same-number { background: rgba(58,163,255,.12); }
.bold-r { border-bottom:2px solid #3a4b66; }
.bold-c { border-right:2px solid #3a4b66; }
footer { text-align:center; color:var(--muted); padding-bottom:24px; }
@media (max-width:560px){
  .board { grid-template-columns: repeat(9, 36px); }
  .cell { width:36px; height:36px; }
}