:root{
  /* slate-and-indigo puzzle theme */
  --bg:#e9edf5;--bg2:#f5f7fb;--ink:#1f2737;--mut:#5b6678;--card:#ffffff;--line:#d6dceb;
  --board:#ffffff;--grid-thin:#c4ccde;--grid-thick:#3a4663;
  --accent:#4f5bd5;--accent-ink:#3a45b0;--accent-soft:#e7e9fb;
  --ok:#1f9d55;--ok-ink:#137a40;--bad:#d64545;--bad-soft:#fde3e3;
  --sel:#4f5bd5;--sel-soft:#dfe2fb;--same:#eef0fc;--given:#eef1f7;--given-ink:#1f2737;
  --pad:#f1f4fa;--pad-line:#cfd6e6;
}
@media(prefers-color-scheme:dark){:root{
  --bg:#161a24;--bg2:#1d2230;--ink:#e8ecf6;--mut:#9aa4ba;--card:#222838;--line:#333c52;
  --board:#1c2130;--grid-thin:#3a445c;--grid-thick:#aeb8d6;
  --accent:#8b93f0;--accent-ink:#aab0f6;--accent-soft:#2b3050;
  --ok:#54c281;--ok-ink:#85d8a4;--bad:#e8807d;--bad-soft:#3a2630;
  --sel:#8b93f0;--sel-soft:#2f3563;--same:#272d45;--given:#272d3c;--given-ink:#e8ecf6;
  --pad:#272d3c;--pad-line:#3a445c;
}}
*{box-sizing:border-box}
html,body{margin:0}
body{font:16px/1.5 -apple-system,BlinkMacSystemFont,"Segoe UI",system-ui,sans-serif;color:var(--ink);
  background:radial-gradient(120% 80% at 50% -10%,var(--bg2),var(--bg));min-height:100vh;
  display:flex;justify-content:center;padding:18px 14px 36px;-webkit-tap-highlight-color:transparent;
  -webkit-text-size-adjust:100%;touch-action:manipulation}
.wrap{width:100%;max-width:480px}

header{display:flex;align-items:center;justify-content:space-between;gap:10px;flex-wrap:wrap;margin-bottom:2px}
.brand{min-width:0}
h1{font-size:clamp(19px,5vw,25px);margin:0;letter-spacing:-.01em}
.tools{display:flex;align-items:center;gap:7px}
.toolbtn{background:var(--card);border:1px solid var(--line);color:var(--accent-ink);border-radius:999px;
  padding:7px 13px;font-size:13px;font-weight:600;cursor:pointer;white-space:nowrap}
.toolbtn:hover{border-color:var(--accent)}
.stat{background:var(--card);border:1px solid var(--line);color:var(--ink);border-radius:999px;
  padding:7px 12px;font:700 13px/1 ui-monospace,monospace;white-space:nowrap}
#timer::before{content:"⏱ ";font-weight:400;color:var(--mut)}
.gc{font:700 13px/1 ui-monospace,monospace;color:#fff;background:var(--accent);text-decoration:none;
  border-radius:999px;padding:7px 12px}
.sub{color:var(--mut);font-size:14px;margin:10px 2px 12px}
.sub b{color:var(--ink)}

/* ---- difficulty badge + actions ---- */
.controls{display:flex;align-items:center;gap:8px;flex-wrap:wrap;margin:10px 0 12px}
.diff{display:inline-flex;align-items:center;gap:6px;border:1px solid var(--pad-line);background:var(--card);
  color:var(--ink);border-radius:999px;padding:6px 13px;font:600 13px/1 system-ui}
.diff::before{content:"";width:9px;height:9px;border-radius:50%;background:var(--mut)}
.diff-easy::before{background:#1f9d55}
.diff-medium::before{background:#e0a800}
.diff-hard::before{background:#d64545}
.spacer{flex:1}
.ghost{background:var(--card);border:1px solid var(--pad-line);color:var(--accent-ink);border-radius:10px;
  padding:8px 13px;font-size:13.5px;font-weight:600;cursor:pointer;white-space:nowrap}
.ghost:hover{border-color:var(--accent)}

/* ---- board ---- */
.boardwrap{display:flex;justify-content:center}
.board{display:grid;grid-template-columns:repeat(var(--n,9),1fr);width:min(94vw,440px);aspect-ratio:1/1;
  background:var(--board);border:3px solid var(--grid-thick);border-radius:10px;overflow:hidden;
  box-shadow:0 6px 20px rgba(20,28,55,.12);user-select:none;-webkit-user-select:none}
.cell{position:relative;border-right:1px solid var(--grid-thin);border-bottom:1px solid var(--grid-thin);
  display:flex;align-items:center;justify-content:center;cursor:pointer;background:transparent;
  transition:background .08s}
.cell.br{border-right:3px solid var(--grid-thick)}
.cell.bb{border-bottom:3px solid var(--grid-thick)}
.cell.edge-r{border-right:0}.cell.edge-b{border-bottom:0}
.cell .val{display:flex;align-items:center;justify-content:center;width:100%;height:100%}
.cell .val .emoji{font:400 clamp(15px,5.2vw,24px)/1 "Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji",system-ui}
.cell .val .shape{width:clamp(17px,5.6vw,26px);height:clamp(17px,5.6vw,26px);display:block}
.cell .val .ps-img{width:clamp(22px,7.4vw,36px);height:auto;display:block;-webkit-user-drag:none}
.cell.given{background:var(--given)}
.cell.given .val{opacity:1}
.cell.same{background:var(--same)}
.cell.sel{background:var(--sel-soft);box-shadow:inset 0 0 0 2px var(--sel);z-index:2}
.cell.conflict{background:var(--bad-soft)}
.cell.conflict .val .emoji{filter:none}
/* pencil marks: small candidate pictures in a 3×3 grid */
.cell .notes{position:absolute;inset:0;display:grid;grid-template-columns:repeat(3,1fr);
  grid-template-rows:repeat(3,1fr);padding:2px;pointer-events:none}
.cell .notes span{display:flex;align-items:center;justify-content:center;overflow:hidden}
.cell .notes span .emoji{font-size:clamp(6px,1.9vw,9px);line-height:1}
.cell .notes span .shape{width:clamp(6px,1.9vw,9px);height:clamp(6px,1.9vw,9px)}
.cell .notes span .ps-img{width:clamp(7px,2.1vw,10px);height:auto}

/* ---- picture tray ---- */
.pad{display:grid;grid-template-columns:repeat(var(--cols,9),1fr);gap:5px;margin:16px 0 4px}
.key{background:var(--pad);border:1px solid var(--pad-line);color:var(--ink);border-radius:11px;
  padding:13px 0;font:600 19px/1 system-ui;cursor:pointer;display:flex;align-items:center;justify-content:center}
.key:hover{border-color:var(--accent)}
.key:active{transform:translateY(1px)}
.key.icon{padding:9px 0}
.key.icon .emoji{font:400 clamp(17px,5.6vw,26px)/1 "Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji",system-ui}
.key.icon .shape{width:clamp(18px,6vw,28px);height:clamp(18px,6vw,28px)}
.key.icon .ps-img{width:clamp(20px,6.4vw,30px);height:auto;display:block;-webkit-user-drag:none}
.key.wide{font-size:14px;font-weight:600;color:var(--accent-ink)}
.key.on{background:var(--accent);border-color:var(--accent);color:#fff}
.padrow{display:flex;gap:7px;margin-top:7px}
.padrow .key{flex:1;aspect-ratio:auto;padding:13px 0}

#msg{text-align:center;min-height:1.3em;margin:12px 2px 0;font-size:14px;color:var(--mut)}
#msg.bad{color:var(--bad)}
#msg.ok{color:var(--ok-ink);font-weight:600}

/* ---- end / reveal card ---- */
.end{display:none;text-align:center;background:var(--card);border:1px solid var(--line);border-radius:18px;
  padding:22px 18px;margin-top:18px;box-shadow:0 8px 26px rgba(20,28,55,.14)}
.end.show{display:block;animation:pop .25s ease}
@keyframes pop{from{transform:scale(.96);opacity:.4}to{transform:scale(1);opacity:1}}
.end h2{margin:.1em 0;font-size:23px;color:var(--ok-ink)}
.end .esub{color:var(--mut);font-size:14px;margin:6px 0 0}
.end img{max-width:100%;height:auto;border-radius:12px;margin:14px auto 0}
.kw{margin:16px 0 6px}
.kw .label{font:600 11px/1 system-ui;text-transform:uppercase;letter-spacing:.1em;color:var(--mut)}
.kw .val{font:800 clamp(20px,6vw,26px)/1.2 ui-monospace,monospace;color:var(--accent-ink);
  margin-top:8px;word-break:break-word}
.row2{display:flex;gap:10px;justify-content:center;margin-top:16px;flex-wrap:wrap}
.btn{background:var(--accent);border:0;color:#fff;border-radius:11px;padding:11px 18px;font-size:15px;
  font-weight:600;cursor:pointer}
.btn.sec{background:var(--card);border:1px solid var(--pad-line);color:var(--accent-ink)}

/* ---- rules modal ---- */
.modal{position:fixed;inset:0;background:rgba(15,20,35,.55);display:none;align-items:center;
  justify-content:center;padding:18px;z-index:50}
.modal.show{display:flex}
.sheet{background:var(--card);border-radius:16px;max-width:420px;width:100%;padding:22px;
  max-height:86vh;overflow:auto}
.sheet h2{margin:0 0 10px;font-size:20px}
.sheet p,.sheet li{color:var(--mut);font-size:14.5px}
.sheet b{color:var(--ink)}
.sheet .close{margin-top:14px;width:100%;background:var(--accent);border:0;color:#fff;border-radius:11px;
  padding:12px;font-size:15px;font-weight:600;cursor:pointer}

@media (max-width:380px){
  .key.wide{padding:11px 0;font-size:14px}
}