/* Precise Logic — site styles. No external fonts or frameworks, for speed. */
:root{
  --ink:#0f1b3d; --ink-2:#33415c; --muted:#64748b; --line:#e2e8f0; --bg:#f7f8fb; --card:#fff;
  --brand:#0d9488; --brand-2:#14b8a6; --brand-soft:#ccfbf1; --amber:#f59e0b; --amber-soft:#fef3c7;
  --navy:#1e3a8a; --bad:#dc2626; --bad-soft:#fee2e2; --hint:#facc15; --hint-soft:#fef9c3;
  --radius:14px; --shadow:0 1px 2px rgba(15,27,61,.06),0 8px 24px rgba(15,27,61,.06);
  --font:system-ui,-apple-system,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  --mono:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;font-family:var(--font);color:var(--ink);background:var(--bg);line-height:1.55;font-size:16px}
a{color:var(--brand);text-decoration-thickness:1px;text-underline-offset:2px}
a:hover{color:var(--ink)}
img,svg{display:block}
.wrap{max-width:1040px;margin:0 auto;padding:0 20px}
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);border:0}
.skip{position:absolute;left:-999px;top:8px;background:var(--ink);color:#fff;padding:8px 12px;border-radius:8px;z-index:50}
.skip:focus{left:8px}

/* header */
.site-header{background:var(--card);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:20}
.site-header .wrap{display:flex;align-items:center;justify-content:space-between;height:62px}
.brand{display:flex;align-items:center;gap:10px;color:var(--ink);text-decoration:none;font-weight:750;font-size:1.15rem;letter-spacing:-.01em}
.brand svg{width:32px;height:32px}
.brand span b{color:var(--brand)}
.nav{display:flex;gap:4px}
.nav a{color:var(--ink-2);text-decoration:none;padding:8px 12px;border-radius:10px;font-weight:550;font-size:.95rem}
.nav a:hover,.nav a[aria-current=page]{background:var(--bg);color:var(--ink)}
.nav-toggle{display:none;background:none;border:1px solid var(--line);border-radius:10px;padding:8px 10px;cursor:pointer;color:var(--ink)}
@media (max-width:720px){
  .nav-toggle{display:block}
  .nav{display:none;position:absolute;top:62px;left:0;right:0;background:var(--card);border-bottom:1px solid var(--line);flex-direction:column;padding:8px 12px 14px}
  .nav.open{display:flex}
}

/* layout */
main{padding:28px 0 48px}
.hero{display:flex;align-items:flex-end;justify-content:space-between;gap:16px;flex-wrap:wrap;margin-bottom:18px}
.hero h1{margin:0;font-size:clamp(1.5rem,3.4vw,2.1rem);letter-spacing:-.02em;line-height:1.15}
.hero p{margin:4px 0 0;color:var(--muted)}
.pill{display:inline-flex;align-items:center;gap:6px;background:var(--brand-soft);color:#115e59;border-radius:999px;padding:4px 10px;font-size:.82rem;font-weight:650}
.pill.archive{background:var(--amber-soft);color:#92400e}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);padding:22px}
.prose{max-width:720px}
.prose h1{font-size:clamp(1.6rem,3.6vw,2.2rem);letter-spacing:-.02em;margin:0 0 12px;line-height:1.2}
.prose h2{margin-top:30px;font-size:1.25rem}
.prose li{margin:4px 0}
.muted{color:var(--muted)}
.grid-2{display:grid;grid-template-columns:minmax(0,1fr) 300px;gap:22px;align-items:start}
@media (max-width:880px){.grid-2{grid-template-columns:1fr}}

/* tabs */
.tabs{display:flex;gap:6px;background:var(--card);border:1px solid var(--line);padding:5px;border-radius:12px;width:max-content;max-width:100%}
.tab{appearance:none;border:0;background:none;padding:9px 16px;border-radius:9px;font:inherit;font-weight:650;color:var(--ink-2);cursor:pointer;display:flex;gap:8px;align-items:center}
.tab[aria-selected=true]{background:var(--ink);color:#fff}
.tab .tick{color:var(--brand-2);font-weight:800}

/* game */
.game{margin-top:16px}
.game-bar{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-bottom:14px;flex-wrap:wrap}
.game-meta{display:flex;gap:14px;align-items:center;color:var(--muted);font-size:.92rem;flex-wrap:wrap}
.timer{font-family:var(--mono);font-size:1.05rem;color:var(--ink);font-weight:650;background:var(--bg);border:1px solid var(--line);padding:3px 10px;border-radius:8px;min-width:68px;text-align:center}
.board-wrap{display:flex;justify-content:center}
.board{--n:6;display:grid;grid-template-columns:repeat(var(--n),1fr);grid-template-rows:repeat(var(--n),1fr);width:min(100%,432px);aspect-ratio:1;border:2px solid var(--ink);border-radius:10px;overflow:hidden;background:var(--ink);gap:1px;touch-action:manipulation;user-select:none;-webkit-user-select:none}
.cell{appearance:none;border:0;margin:0;padding:0;background:#fff;font:inherit;color:var(--ink);display:flex;align-items:center;justify-content:center;cursor:pointer;position:relative;font-size:clamp(1.2rem,5vw,1.7rem);font-weight:650;-webkit-tap-highlight-color:transparent}
.cell:focus-visible{outline:3px solid var(--brand-2);outline-offset:-3px;z-index:1}
.cell.given{background:#eef2f7;cursor:default;font-weight:800}
.cell.hinted{background:var(--hint-soft)}
.cell.selected{background:var(--brand-soft)}
.cell.peer{background:#f1f7f7}
.cell.peer.given{background:#e4edf0}
.cell.same{color:var(--brand)}
.board.solved .cell{animation:pop .5s ease both}
@keyframes pop{50%{transform:scale(.92)}}
/* sudoku box borders */
.board.sudoku .cell.br{box-shadow:inset -2px 0 0 var(--ink)}
.board.sudoku .cell.bb{box-shadow:inset 0 -2px 0 var(--ink)}
.board.sudoku .cell.br.bb{box-shadow:inset -2px 0 0 var(--ink),inset 0 -2px 0 var(--ink)}
.board.sudoku .cell.given{color:var(--ink)}
.board.sudoku .cell:not(.given){color:var(--brand)}
/* binary discs */
.disc{width:62%;height:62%;border-radius:50%;display:flex;align-items:center;justify-content:center;transition:transform .12s}
.disc svg{width:58%;height:58%}
.disc.v0{background:var(--amber);color:#fff}
.disc.v1{background:var(--navy);color:#fff}
.cell.given .disc{box-shadow:inset 0 0 0 3px rgba(255,255,255,.55)}

.controls{display:flex;gap:8px;justify-content:center;margin-top:16px;flex-wrap:wrap}
.btn{appearance:none;border:1px solid var(--line);background:var(--card);color:var(--ink);font:inherit;font-weight:650;padding:10px 16px;border-radius:10px;cursor:pointer;display:inline-flex;align-items:center;gap:8px;text-decoration:none;line-height:1.2}
.btn:hover{border-color:#cbd5e1;background:#f8fafc;color:var(--ink)}
.btn.primary{background:var(--ink);color:#fff;border-color:var(--ink)}
.btn.primary:hover{background:#1e2b52}
.btn.brand{background:var(--brand);border-color:var(--brand);color:#fff}
.btn:disabled{opacity:.5;cursor:not-allowed}
.numpad{display:grid;grid-template-columns:repeat(7,1fr);gap:6px;width:min(100%,432px);margin:14px auto 0}
.numpad button{appearance:none;border:1px solid var(--line);background:var(--card);border-radius:10px;padding:12px 0;font:inherit;font-weight:750;font-size:1.15rem;color:var(--ink);cursor:pointer}
.numpad button:hover{background:var(--brand-soft)}
.status{min-height:1.6em;text-align:center;margin-top:12px;font-weight:600;color:var(--ink-2)}
.status.good{color:var(--brand)}
.status.bad{color:var(--bad)}
.legend{display:flex;gap:16px;justify-content:center;margin-top:10px;color:var(--muted);font-size:.88rem;flex-wrap:wrap}
.legend span{display:inline-flex;align-items:center;gap:6px}
.legend .disc{width:18px;height:18px}

/* result panel */
.result{margin-top:18px;border:2px solid var(--brand-2);background:linear-gradient(180deg,#f0fdfa,#fff);border-radius:var(--radius);padding:18px;text-align:center}
.result h2{margin:0 0 4px;font-size:1.3rem}
.result .stats{display:flex;justify-content:center;gap:22px;margin:12px 0;flex-wrap:wrap}
.result .stat b{display:block;font-size:1.4rem}
.result .stat small{color:var(--muted)}
.result .share-row{display:flex;gap:8px;justify-content:center;flex-wrap:wrap}
.share-preview{font-family:var(--mono);white-space:pre;background:#fff;border:1px dashed var(--line);border-radius:10px;padding:10px;margin:12px auto 0;display:inline-block;text-align:left;font-size:.85rem;line-height:1.35}

/* sidebar */
.side{display:flex;flex-direction:column;gap:16px}
.side h3{margin:0 0 8px;font-size:1rem}
.streak{display:flex;gap:12px}
.streak div{flex:1;background:var(--bg);border-radius:10px;padding:10px;text-align:center}
.streak b{display:block;font-size:1.5rem;line-height:1.1}
.streak small{color:var(--muted);font-size:.8rem}
.newsletter form{display:flex;flex-direction:column;gap:8px}
.newsletter input{font:inherit;padding:10px 12px;border:1px solid var(--line);border-radius:10px}
.newsletter .todo{font-size:.78rem;color:var(--muted)}
.mini-list{list-style:none;margin:0;padding:0}
.mini-list li{display:flex;justify-content:space-between;padding:6px 0;border-bottom:1px solid var(--line);font-size:.93rem}
.mini-list li:last-child{border:0}

/* ad slots: reserved, collapse while empty */
.ad-slot{margin:18px auto;text-align:center;min-height:0}
.ad-slot:empty{display:none}

/* archive */
.archive-month{margin:26px 0 10px;font-size:1.05rem;color:var(--ink-2)}
.archive-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(230px,1fr));gap:12px}
.day{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:14px;display:flex;flex-direction:column;gap:8px}
.day header{display:flex;justify-content:space-between;align-items:baseline}
.day header b{font-size:.98rem}
.day header small{color:var(--muted)}
.day .links{display:flex;gap:6px}
.day .links a{flex:1;text-align:center;text-decoration:none;border:1px solid var(--line);border-radius:8px;padding:7px 6px;font-weight:600;font-size:.88rem;color:var(--ink-2)}
.day .links a:hover{background:var(--bg)}
.day .links a.done{background:var(--brand-soft);border-color:#99f6e4;color:#115e59}
.day .diff{font-size:.78rem;color:var(--muted)}

/* how-to visuals */
.example{display:grid;gap:4px;grid-template-columns:repeat(6,34px);margin:12px 0}
.example .x{width:34px;height:34px;border:1px solid var(--line);border-radius:6px;display:flex;align-items:center;justify-content:center;background:#fff;font-weight:700}
.example .x .disc{width:22px;height:22px}

/* footer */
.site-footer{border-top:1px solid var(--line);background:var(--card);padding:26px 0;font-size:.9rem;color:var(--muted)}
.site-footer .wrap{display:flex;justify-content:space-between;gap:16px;flex-wrap:wrap}
.site-footer nav{display:flex;gap:14px;flex-wrap:wrap}
.site-footer a{color:var(--ink-2)}
.for-sale{margin-top:6px;font-size:.84rem}
.for-sale a{color:var(--muted)}

.toast{position:fixed;left:50%;bottom:24px;transform:translateX(-50%) translateY(20px);background:var(--ink);color:#fff;padding:10px 16px;border-radius:10px;opacity:0;transition:.25s;pointer-events:none;z-index:60;font-weight:600}
.toast.show{opacity:1;transform:translateX(-50%) translateY(0)}
@media (prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}}

/* word ladder */
.ladder-goal{text-align:center;margin:0 0 12px;color:var(--ink-2)}
.ladder{display:flex;flex-direction:column;align-items:center;gap:6px}
.ladder-row{display:flex;gap:6px}
.tile{width:clamp(40px,12vw,50px);height:clamp(40px,12vw,50px);border:2px solid var(--line);border-radius:9px;display:flex;align-items:center;justify-content:center;font-weight:800;font-size:clamp(1.15rem,5vw,1.45rem);text-transform:uppercase;background:#fff;color:var(--ink)}
.ladder-row.start .tile{background:var(--ink);border-color:var(--ink);color:#fff}
.ladder-row.step .tile.changed{background:var(--brand);border-color:var(--brand);color:#fff}
.ladder-row.hinted .tile.changed{background:var(--hint);border-color:var(--hint);color:var(--ink)}
.ladder-row.done .tile{border-color:var(--brand-2)}
.ladder-row.entry .tile{border-style:solid;border-color:#cbd5e1}
.ladder-row.entry .tile.filled{border-color:var(--ink)}
.ladder-row.entry .tile:not(.filled):first-of-type,.ladder-row.entry .tile.filled+.tile:not(.filled){border-color:var(--brand-2);box-shadow:0 0 0 2px var(--brand-soft)}
.ladder-row.target .tile{border-style:dashed;border-color:var(--amber);background:var(--amber-soft);color:#92400e}
.ladder-gap{color:var(--muted);line-height:1;font-size:1.2rem}
.par{background:var(--bg);border:1px solid var(--line);border-radius:999px;padding:1px 9px;font-size:.84rem}
.kb{display:flex;flex-direction:column;gap:6px;margin:16px auto 0;width:min(100%,480px);touch-action:manipulation}
.kb[hidden]{display:none}
.kb-row{display:flex;gap:5px;justify-content:center}
.kb button{appearance:none;flex:1 1 0;min-width:0;max-width:44px;height:50px;border:0;border-radius:8px;background:#e2e8f0;color:var(--ink);font:inherit;font-weight:700;font-size:1rem;text-transform:uppercase;cursor:pointer;padding:0;-webkit-tap-highlight-color:transparent}
.kb button.wide{flex:1.6 1 0;max-width:70px;font-size:.8rem}
.kb button:active{background:#cbd5e1}
.day .links{flex-wrap:wrap}
.day .links a{min-width:30%}
@media (max-width:560px){
  .hero .tabs{width:100%}
  .tab{flex:1 1 0;justify-content:center;padding:9px 6px;white-space:nowrap;font-size:.9rem;gap:4px}
  .game-bar{flex-wrap:nowrap;align-items:flex-start}
  .game-meta{gap:4px 10px;font-size:.85rem}
  .card.game{padding:16px 12px}
}
.result.under-par{border-color:var(--amber);background:linear-gradient(180deg,#fffbeb,#fff)}
.result.under-par h2{color:#92400e}
/* broken-rule notes under the grid (text only, no cell highlighting) */
.rules{width:min(100%,432px);margin:10px auto 0}
.rules:empty{display:none}
.rules-head{margin:0 0 4px;font-weight:700;color:var(--bad);font-size:.92rem}
.rules ul{margin:0;padding:10px 12px 10px 28px;background:var(--bad-soft);border:1px solid #fecaca;border-radius:10px;color:#7f1d1d;font-size:.92rem;line-height:1.4}
.rules li{margin:2px 0}
.rules li.more{list-style:none;margin-left:-16px;color:var(--muted);font-weight:600}
/* binary: right-click hint only where there is a mouse; no long-press callout on the grid */
.board{-webkit-touch-callout:none}
.legend .how,.legend .rc{display:inline}
@media (hover:none),(pointer:coarse){.legend .rc{display:none}}
.using-mouse .legend .rc{display:inline}
.using-touch .legend .rc{display:none}