#sudoku-arena{
  --bg:#ffffff; --bg2:#f3f6fa; --panel:#ffffff;
  --ink:#344861; --ink2:#6a7690; --faint:#94a3b8;
  --blue:#325aaf; --blue-bright:#4a7bd0; --blue-pale:#eaeef4;
  --sel:#bbdefb; --peer:#e2ebf3; --same:#cbdbed;
  --err:#e55c6c; --err-bg:#f7cfd6;
  --hint-bg:#fff3c4;
  --line-thin:#d0d8e5; --line-thick:#344861;
  --green:#2e9e5b;
  --r:10px;
  font-family:'Inter',system-ui,-apple-system,sans-serif;
}
#sudoku-arena, #sudoku-arena *{box-sizing:border-box;margin:0;padding:0;-webkit-tap-highlight-color:transparent}
#sudoku-arena{font-family:'Inter',system-ui,sans-serif;background:var(--bg);color:var(--ink);line-height:1.4}
#sudoku-arena button{font-family:inherit;cursor:pointer}
#sudoku-arena .wrap{max-width:960px;margin:0 auto;padding:12px 14px 48px}
#sudoku-arena /* ---------- header ---------- */
header{display:flex;align-items:center;gap:10px;padding:6px 0 12px;border-bottom:1px solid #e7ecf3;margin-bottom:12px}
#sudoku-arena .logo{display:flex;align-items:center;gap:9px;font-weight:800;font-size:19px;letter-spacing:-.02em}
#sudoku-arena .logo .cube{width:28px;height:28px;border-radius:7px;background:var(--blue);color:#fff;display:flex;align-items:center;justify-content:center;font-size:15px;font-weight:800}
#sudoku-arena .logo span b{color:var(--blue)}
#sudoku-arena .who{margin-left:auto;text-align:right}
#sudoku-arena .who button{background:none;border:none;font-weight:600;font-size:13px;color:var(--blue)}
#sudoku-arena .who small{display:block;font-size:10.5px;color:var(--faint)}
#sudoku-arena .offline{display:none;font-size:10px;font-weight:700;letter-spacing:.06em;color:#b45309;background:#fef3c7;border-radius:4px;padding:2px 6px;margin-top:2px}
#sudoku-arena /* ---------- tabs ---------- */
nav{display:flex;gap:6px;background:var(--bg2);padding:4px;border-radius:12px;margin-bottom:14px}
#sudoku-arena nav button{flex:1;padding:9px 4px;font-weight:600;font-size:13.5px;border:none;border-radius:9px;background:transparent;color:var(--ink2)}
#sudoku-arena nav button.on{background:#fff;color:var(--blue);box-shadow:0 1px 3px rgba(52,72,97,.15)}
#sudoku-arena button:focus-visible{outline:2px solid var(--blue);outline-offset:2px}
#sudoku-arena /* ---------- lobby panels ---------- */
.panel{background:var(--panel);border:1px solid #e7ecf3;border-radius:14px;padding:18px;box-shadow:0 2px 8px rgba(52,72,97,.06)}
#sudoku-arena .panel h2{font-size:19px;font-weight:700;margin-bottom:4px;letter-spacing:-.01em}
#sudoku-arena .panel .sub{font-size:13px;color:var(--ink2);line-height:1.5;margin-bottom:14px}
#sudoku-arena .chips{display:flex;gap:6px;flex-wrap:wrap;margin-bottom:14px}
#sudoku-arena .chip{padding:8px 14px;border-radius:999px;border:1.5px solid #dbe3ee;background:#fff;font-weight:600;font-size:13px;color:var(--ink2)}
#sudoku-arena .chip.on{background:var(--blue);border-color:var(--blue);color:#fff}
#sudoku-arena .btn{display:inline-flex;align-items:center;justify-content:center;gap:6px;padding:12px 22px;border:none;border-radius:11px;background:var(--blue);color:#fff;font-weight:700;font-size:15px;box-shadow:0 3px 10px rgba(50,90,175,.3);transition:transform .06s}
#sudoku-arena .btn:active{transform:scale(.97)}
#sudoku-arena .btn.line{background:#fff;color:var(--blue);border:1.5px solid #dbe3ee;box-shadow:none}
#sudoku-arena .btn.big{width:100%;padding:14px}
#sudoku-arena .btn:disabled{opacity:.5}
#sudoku-arena .note{font-size:12px;color:var(--faint);margin-top:12px;line-height:1.5}
#sudoku-arena .badge{display:inline-block;font-size:10.5px;font-weight:700;letter-spacing:.09em;text-transform:uppercase;color:var(--blue);background:var(--blue-pale);border-radius:5px;padding:3px 8px;margin-bottom:8px}
#sudoku-arena /* leaderboard */
table.lb{width:100%;border-collapse:collapse;font-size:13.5px}
#sudoku-arena table.lb td{padding:8px 4px;border-bottom:1px solid #eef2f7}
#sudoku-arena table.lb tr.me td{background:var(--blue-pale);font-weight:600}
#sudoku-arena td.rank{width:30px;font-weight:700;color:var(--ink2)}
#sudoku-arena td.t{text-align:right;font-variant-numeric:tabular-nums;font-weight:600}
#sudoku-arena td.mm{text-align:right;color:var(--faint);font-size:12px}
#sudoku-arena .empty{font-size:13px;color:var(--faint);padding:14px 4px;text-align:center}
#sudoku-arena /* ---------- game layout ---------- */
#game{display:none}
#sudoku-arena #game.on{display:grid;gap:14px;grid-template-areas:"hud" "board" "side"}
#sudoku-arena .hud{grid-area:hud;display:flex;align-items:center;gap:8px}
#sudoku-arena .hud .stat{flex:1;background:var(--bg2);border-radius:10px;padding:7px 10px;text-align:center}
#sudoku-arena .hud .stat small{display:block;font-size:10px;font-weight:600;letter-spacing:.06em;text-transform:uppercase;color:var(--faint)}
#sudoku-arena .hud .stat b{font-size:15px;font-variant-numeric:tabular-nums;font-weight:700}
#sudoku-arena .hud .stat b .err3{color:var(--err)}
#sudoku-arena #pauseBtn{border:none;background:var(--bg2);border-radius:10px;width:42px;align-self:stretch;font-size:15px;color:var(--ink)}
#sudoku-arena .boardWrap{grid-area:board;display:flex;flex-direction:column;align-items:center;gap:10px}
#sudoku-arena #board{position:relative;display:grid;grid-template-columns:repeat(9,1fr);grid-template-rows:repeat(9,1fr);
  border:3px solid var(--line-thick);border-radius:8px;overflow:hidden;background:#fff;touch-action:manipulation}
#sudoku-arena .gridlines{position:absolute;inset:0;width:100%;height:100%;pointer-events:none;z-index:5}
#sudoku-arena .cell{position:relative;display:flex;align-items:center;justify-content:center;background:#fff;font-weight:500;user-select:none;cursor:pointer;color:var(--blue)}
#sudoku-arena .cell.given{color:var(--ink)}
#sudoku-arena .cell.wrongv{color:var(--err)}
#sudoku-arena .cell.peer{background:var(--peer)}
#sudoku-arena .cell.same{background:var(--same)}
#sudoku-arena .cell.sel{background:var(--sel)}
#sudoku-arena .cell.wrongbg{background:var(--err-bg)}
#sudoku-arena .cell.hintcell{background:var(--hint-bg)}
#sudoku-arena .cell .notes{position:absolute;inset:2%;display:grid;grid-template-columns:repeat(3,1fr);grid-template-rows:repeat(3,1fr);font-size:.32em;font-weight:600;color:var(--ink2);pointer-events:none}
#sudoku-arena .cell .notes span{display:flex;align-items:center;justify-content:center}
@keyframes sa-shake{0%,100%{transform:translateX(0)}25%{transform:translateX(-3px)}75%{transform:translateX(3px)}}
#sudoku-arena .cell.shake{animation:sa-shake .22s}
@media(prefers-reduced-motion:reduce){
#sudoku-arena .cell.shake{animation:none}
#sudoku-arena .rb .fill{transition:none}
}
#sudoku-arena /* race bars */
.racebars{display:none;flex-direction:column;gap:6px;width:100%}
#sudoku-arena .racebars.on{display:flex}
#sudoku-arena .rb{display:flex;align-items:center;gap:8px;font-size:12.5px;font-weight:600}
#sudoku-arena .rb .name{width:90px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
#sudoku-arena .rb .track{flex:1;height:12px;border-radius:99px;background:var(--bg2);overflow:hidden}
#sudoku-arena .rb .fill{height:100%;width:0%;background:var(--blue-bright);transition:width .4s linear;border-radius:99px}
#sudoku-arena .rb.op .fill{background:var(--err)}
#sudoku-arena .rb .pct{width:38px;text-align:right;font-variant-numeric:tabular-nums;color:var(--ink2)}
#sudoku-arena /* side panel: controls + numpad */
.side{grid-area:side;display:flex;flex-direction:column;gap:12px}
#sudoku-arena .controls{display:flex;justify-content:space-around;gap:6px}
#sudoku-arena .ctl{display:flex;flex-direction:column;align-items:center;gap:4px;border:none;background:none;color:var(--ink2);font-size:11.5px;font-weight:600;position:relative}
#sudoku-arena .ctl .ic{width:50px;height:50px;border-radius:50%;background:var(--blue-pale);display:flex;align-items:center;justify-content:center;font-size:20px;color:var(--ink)}
#sudoku-arena .ctl .tag{position:absolute;top:-2px;right:2px;font-size:8.5px;font-weight:800;background:var(--faint);color:#fff;border-radius:99px;padding:2px 5px}
#sudoku-arena .ctl.on .tag{background:var(--blue)}
#sudoku-arena .ctl:active .ic{background:#dde5f0}
#sudoku-arena #pad{display:grid;grid-template-columns:repeat(9,1fr);gap:6px}
#sudoku-arena #pad button{border:none;border-radius:9px;background:var(--blue-pale);color:var(--blue);
  font-weight:600;font-size:clamp(20px,6vw,26px);padding:10px 0 6px;display:flex;flex-direction:column;align-items:center;line-height:1}
#sudoku-arena #pad button small{font-size:9.5px;font-weight:600;color:var(--faint);margin-top:2px}
#sudoku-arena #pad button.done{opacity:.25}
#sudoku-arena #pad button:active{background:#dde5f0}
#sudoku-arena .sidebtns{display:flex;gap:8px}
#sudoku-arena .sidebtns .btn{flex:1}
#sudoku-arena /* hint box */
.hintbox{display:none;width:100%;background:#f0f6ff;border:1.5px solid var(--blue-bright);border-radius:10px;padding:10px 12px;font-size:13px;line-height:1.5;color:var(--ink)}
#sudoku-arena .hintbox b{color:var(--blue)}
#sudoku-arena /* desktop */{
@media(min-width:760px){
#sudoku-arena #game.on{grid-template-columns:minmax(0,1fr) 290px;grid-template-areas:"board hud" "board side";align-items:start;column-gap:26px}
#sudoku-arena .hud{flex-wrap:wrap}
#sudoku-arena #pad{grid-template-columns:repeat(3,1fr)}
#sudoku-arena #pad button{font-size:30px;padding:16px 0 10px}
}
#sudoku-arena /* overlay */
#overlay{position:fixed;inset:0;background:rgba(52,72,97,.45);display:none;align-items:center;justify-content:center;padding:18px;z-index:60}
#sudoku-arena #overlay.on{display:flex}
#sudoku-arena #overlay .card{width:100%;max-width:380px;background:#fff;border-radius:16px;padding:24px;box-shadow:0 12px 40px rgba(30,40,60,.35);text-align:center}
#sudoku-arena #overlay h2{font-size:22px;font-weight:800;margin-bottom:6px;letter-spacing:-.01em}
#sudoku-arena #overlay .sub2{font-size:13.5px;color:var(--ink2);line-height:1.5}
#sudoku-arena #overlay .big{font-size:42px;font-weight:800;margin:12px 0 2px;font-variant-numeric:tabular-nums;color:var(--blue)}
#sudoku-arena #overlay .stats{display:flex;justify-content:center;gap:18px;margin:12px 0 18px;font-size:12px;color:var(--faint)}
#sudoku-arena #overlay .stats b{display:block;font-size:16px;color:var(--ink);font-variant-numeric:tabular-nums}
#sudoku-arena #overlay input{width:100%;padding:12px;font-size:15px;font-family:inherit;border:1.5px solid #dbe3ee;border-radius:10px;margin:12px 0 16px;text-align:center}
#sudoku-arena #overlay .row{display:flex;gap:8px}
#sudoku-arena #overlay .row .btn{flex:1}
#sudoku-arena .spin{display:inline-block;width:14px;height:14px;border:2px solid #dbe3ee;border-top-color:var(--blue);border-radius:50%;animation:sa-sp 1s linear infinite;vertical-align:-2px}
@keyframes sa-sp{to{transform:rotate(360deg)}}