/* OptemEra — Sudoku. Same tokens as the homepage (assets/home.css). */
:root{
  color-scheme:light;
  --bg:#f5f6f2;--surface:#fff;--surface-2:#eef1ec;--ink:#12201b;--muted:#5a6a63;--line:#dde3dc;--line-strong:#c9d2ca;
  --brand:#0d7a5c;--brand-ink:#fff;--brand-soft:#e3f2ec;--accent:#6845c4;--accent-soft:#efeafc;
  --given:#eef1ec;--wrong:#ffe4df;--danger:#c23d17;--ok:#0b7d68;
  --shadow:0 1px 2px rgba(18,32,27,.05),0 12px 32px rgba(18,32,27,.08);
  --font:-apple-system,BlinkMacSystemFont,"Segoe UI Variable","Segoe UI",Inter,Roboto,"Helvetica Neue",Arial,sans-serif;
}
:root[data-theme=dark]{
  color-scheme:dark;
  --bg:#0c1210;--surface:#141c19;--surface-2:#1b2521;--ink:#e9efec;--muted:#a3b2ab;--line:#25312c;--line-strong:#3a4a42;
  --brand:#4fd1a1;--brand-ink:#06231a;--brand-soft:#14382c;--accent:#a78bfa;--accent-soft:#2a2340;
  --given:#1b2521;--wrong:#4a1f18;--danger:#ff8a7a;--ok:#4fd1a1;--shadow:0 18px 40px rgba(0,0,0,.4);
}
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.55 var(--font);-webkit-font-smoothing:antialiased}
button,input,select{font:inherit;color:inherit}
:focus-visible{outline:2px solid var(--brand);outline-offset:3px}

/* Header */
.site-header{position:sticky;top:0;z-index:10;display:flex;align-items:center;gap:16px;min-height:64px;padding:0 max(16px,calc((100% - 1160px)/2));
  background:color-mix(in srgb,var(--bg) 88%,transparent);backdrop-filter:blur(14px);-webkit-backdrop-filter:blur(14px);border-bottom:1px solid var(--line)}
.brand{font-size:21px;font-weight:800;letter-spacing:-.04em;color:var(--ink);text-decoration:none}
.brand-dot{color:var(--brand)}
.header-note{color:var(--muted);font-size:14px;font-weight:600}
.header-note::before{content:"/";margin-right:12px;color:var(--line-strong);font-weight:300}
.theme-toggle{margin-left:auto;min-height:38px;padding:0 14px;border-radius:999px;border:1px solid var(--line-strong);background:var(--surface);font-size:13px;font-weight:600;cursor:pointer}
.theme-toggle:hover{border-color:var(--ink)}

main{width:min(1160px,100% - 32px);margin:0 auto;padding:clamp(28px,6vw,64px) 0 64px}

/* Hero */
.hero{display:flex;align-items:end;justify-content:space-between;gap:24px;margin-bottom:clamp(24px,4vw,40px)}
.eyebrow{display:inline-flex;align-items:center;gap:8px;margin-bottom:16px;padding:6px 12px 6px 10px;border:1px solid var(--line-strong);border-radius:999px;background:var(--surface);color:var(--muted);font-size:13px;font-weight:600}
.eyebrow::before{content:"";width:8px;height:8px;border-radius:50%;background:var(--accent);box-shadow:0 0 0 4px var(--accent-soft)}
.hero h1{margin:0;font-size:clamp(38px,6vw,68px);line-height:1;letter-spacing:-.045em;font-weight:800}
.hero p{margin:16px 0 0;max-width:56ch;color:var(--muted);font-size:clamp(16px,1.6vw,18px)}
.hero-stat{flex:none;display:grid;justify-items:center;min-width:132px;padding:18px 22px;border-radius:20px;background:var(--surface);border:1px solid var(--line);box-shadow:var(--shadow)}
.hero-stat strong{font-size:44px;line-height:1;letter-spacing:-.04em;color:var(--accent);font-variant-numeric:tabular-nums}
.hero-stat span{margin-top:6px;color:var(--muted);font-size:13px;font-weight:600}

/* Workspace */
.workspace{display:grid;grid-template-columns:minmax(0,1fr) 340px;gap:24px;align-items:start}
.puzzle-sheet,.controls{background:var(--surface);border:1px solid var(--line);border-radius:24px;box-shadow:var(--shadow)}
.puzzle-sheet{padding:clamp(16px,3vw,32px)}
.sheet-top,.sheet-bottom{display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap}
.sheet-top{margin-bottom:20px}
.sheet-title{margin:0;font-size:22px;letter-spacing:-.02em}
.sheet-title span{color:var(--accent)}
.sheet-meta{color:var(--muted);font-size:13px}
.seed-chip{padding:6px 12px;border-radius:999px;background:var(--surface-2);border:1px solid var(--line);color:var(--muted);font:600 12px/1.4 ui-monospace,SFMono-Regular,Menlo,monospace;letter-spacing:.04em}
.sheet-bottom{margin-top:18px;color:var(--muted);font-size:13px}

/* Board */
#board{display:grid;grid-template-columns:repeat(9,1fr);width:min(100%,560px);margin:0 auto;aspect-ratio:1;gap:0;
  border:2.5px solid var(--ink);border-radius:12px;overflow:hidden;background:var(--surface)}
.cell{display:grid;place-items:center;min-width:0;aspect-ratio:1;background:var(--surface);color:var(--ink);
  font-size:clamp(18px,3.6vw,30px);font-weight:700;font-variant-numeric:tabular-nums;
  border-right:1px solid var(--line-strong);border-bottom:1px solid var(--line-strong)}
.cell:nth-child(3n){border-right:2.5px solid var(--ink)}
.cell:nth-child(9n){border-right:0}
.cell:nth-child(n+19):nth-child(-n+27),.cell:nth-child(n+46):nth-child(-n+54){border-bottom:2.5px solid var(--ink)}
.cell:nth-child(n+73){border-bottom:0}
.cell.given{background:var(--given)}
.cell input{width:100%;height:100%;border:0;padding:0;background:transparent;color:var(--accent);text-align:center;font:inherit;outline:0;caret-color:var(--accent)}
.cell input:hover{background:var(--accent-soft)}
.cell input:focus{background:var(--accent-soft);box-shadow:inset 0 0 0 2.5px var(--accent)}
.cell.wrong,.cell.wrong input{background:var(--wrong);color:var(--danger)}
.status{min-height:22px;font-weight:650;color:var(--ink)}
.status.ok{color:var(--ok)}
.status.error{color:var(--danger)}

/* Controls */
.controls{position:sticky;top:84px;padding:24px}
.controls h2{margin:0 0 18px;font-size:18px;letter-spacing:-.015em}
.field{margin-bottom:16px}
.field label{display:block;margin-bottom:6px;color:var(--muted);font-size:13px;font-weight:600}
select,.seed-input{width:100%;min-height:44px;padding:0 12px;border-radius:12px;border:1px solid var(--line-strong);background:var(--surface-2)}
.seed-input{font-family:ui-monospace,SFMono-Regular,Menlo,monospace;text-transform:uppercase;letter-spacing:.06em}
.seed-row{display:flex;gap:8px}
.seed-row .seed-input{flex:1;min-width:0}
.actions{display:grid;gap:8px;margin:22px 0 18px}
.button{display:inline-flex;align-items:center;justify-content:center;min-height:46px;padding:0 18px;border-radius:999px;border:1px solid transparent;
  background:var(--ink);color:var(--bg);font-size:14.5px;font-weight:700;cursor:pointer;transition:transform .15s,background .15s,border-color .15s}
.button:hover{transform:translateY(-1px)}
.button.gold{background:var(--brand);color:var(--brand-ink)}
.button.secondary{background:var(--surface);color:var(--ink);border-color:var(--line-strong)}
.button.secondary:hover{border-color:var(--ink)}
.button.small{min-height:44px;padding:0 16px;font-size:13.5px}
.help{padding:14px 16px;border-radius:14px;background:var(--surface-2);color:var(--muted);font-size:13px;line-height:1.55}
.help strong{color:var(--ink)}

@media (max-width:900px){
  .workspace{grid-template-columns:1fr}
  .controls{position:static}
  .actions{grid-template-columns:1fr 1fr}
  .actions .gold,.actions #downloadPdf{grid-column:1/-1}
}
@media (max-width:600px){
  .header-note{display:none}
  .hero{flex-direction:column;align-items:flex-start}
  .hero-stat{flex-direction:row;display:flex;align-items:baseline;gap:8px;min-width:0;padding:10px 16px;border-radius:999px}
  .hero-stat strong{font-size:24px}
  .hero-stat span{margin:0}
  .puzzle-sheet{padding:12px;border-radius:18px}
  .sheet-top{margin-bottom:12px}
  #board{border-radius:8px}
  .actions{grid-template-columns:1fr}
}
@media (prefers-reduced-motion:reduce){.button{transition:none}.button:hover{transform:none}}
@media print{
  .site-header,.controls,.hero-stat{display:none}
  body{background:#fff;color:#000}
  .puzzle-sheet{box-shadow:none;border:0}
}