:root{
  --bg:#f4f6fb; --card:#fff; --ink:#111827; --muted:#4b5563; --line:#d1d5db;
  --brand:#1d4ed8; --brand-ink:#fff; --brand-soft:#dbeafe;
  --ok:#166534; --ok-bg:#dcfce7; --ok-line:#16a34a;
  --bad:#991b1b; --bad-bg:#fee2e2; --bad-line:#dc2626;
  --warn-bg:#fef9c3; --radius:14px;
  --safe-b:env(safe-area-inset-bottom,0px);
}
@media (prefers-color-scheme:dark){
  :root{ --bg:#0b1220; --card:#111a2e; --ink:#f3f4f6; --muted:#cbd5e1; --line:#334155;
    --brand:#60a5fa; --brand-ink:#0b1220; --brand-soft:#1e3a8a;
    --ok:#bbf7d0; --ok-bg:#14532d; --ok-line:#22c55e;
    --bad:#fecaca; --bad-bg:#7f1d1d; --bad-line:#f87171; --warn-bg:#3f3a12; }
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--ink);
  font:17px/1.45 -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  -webkit-tap-highlight-color:transparent;min-height:100vh}
.topbar{position:sticky;top:0;z-index:5;display:flex;align-items:center;gap:.5rem;
  padding:calc(.6rem + env(safe-area-inset-top,0px)) 1rem .6rem;background:var(--brand);color:var(--brand-ink)}
.topbar h1{font-size:1.1rem;margin:0;flex:1;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.iconbtn{background:transparent;border:2px solid currentColor;color:inherit;border-radius:10px;
  min-width:44px;min-height:40px;font-size:1.2rem;cursor:pointer}
.badge{background:rgba(255,255,255,.2);border-radius:999px;padding:.15rem .6rem;font-size:.85rem;font-weight:600}
main{max-width:640px;margin:0 auto;padding:1rem 1rem calc(2rem + var(--safe-b));outline:none}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:1rem;margin:0 0 1rem;
  box-shadow:0 1px 2px rgba(0,0,0,.05)}
h2{font-size:1.25rem;margin:.2rem 0 .6rem}
h3{font-size:1.05rem;margin:.2rem 0 .5rem}
p{margin:.4rem 0}
.muted{color:var(--muted)}
.small{font-size:.9rem}
.stats{display:grid;grid-template-columns:repeat(2,1fr);gap:.6rem}
.stat{background:var(--brand-soft);border-radius:12px;padding:.6rem .8rem}
.stat b{display:block;font-size:1.5rem;line-height:1.1}
.stat span{font-size:.85rem;color:var(--muted)}
@media (prefers-color-scheme:dark){.stat span{color:var(--ink)}}
.btn{display:block;width:100%;min-height:54px;padding:.8rem 1rem;margin:.5rem 0;border-radius:12px;
  border:2px solid var(--brand);background:var(--brand);color:var(--brand-ink);font:inherit;font-weight:700;
  cursor:pointer;text-align:center;text-decoration:none}
.btn.secondary{background:transparent;color:var(--brand)}
.btn.danger{background:transparent;color:var(--bad-line);border-color:var(--bad-line)}
.btn:disabled{opacity:.5;cursor:not-allowed}
.btn:focus-visible,.choice:focus-visible,.chip:focus-visible,select:focus-visible,.iconbtn:focus-visible{outline:3px solid #f59e0b;outline-offset:2px}
.row{display:flex;gap:.6rem}
.row>.btn{flex:1}
.chips{display:flex;flex-wrap:wrap;gap:.5rem;margin:.4rem 0 .6rem}
.chip{min-height:44px;padding:.4rem .9rem;border-radius:999px;border:2px solid var(--brand);background:transparent;
  color:var(--brand);font:inherit;font-weight:600;cursor:pointer}
.chip[aria-pressed="true"]{background:var(--brand);color:var(--brand-ink)}
label.field{display:block;font-weight:600;margin:.4rem 0 .2rem}
select{width:100%;min-height:48px;font:inherit;padding:.4rem .6rem;border-radius:10px;border:2px solid var(--line);
  background:var(--card);color:var(--ink)}
.toggle{display:flex;align-items:center;gap:.6rem;min-height:44px;font-weight:600}
.toggle input{width:24px;height:24px}
.progress{height:8px;background:var(--line);border-radius:99px;overflow:hidden;margin:.2rem 0 .8rem}
.progress>i{display:block;height:100%;background:var(--brand);width:0;transition:width .2s}
.qmeta{display:flex;justify-content:space-between;font-size:.9rem;color:var(--muted);margin-bottom:.3rem}
.question{font-size:1.15rem;font-weight:700;margin:.3rem 0 .8rem}
.signimg{display:flex;justify-content:center;margin:.2rem 0 1rem}
.signimg img{width:min(56vw,220px);height:min(56vw,220px);object-fit:contain}
.choices{list-style:none;margin:0;padding:0}
.choice{display:flex;align-items:flex-start;gap:.7rem;width:100%;min-height:56px;margin:0 0 .6rem;padding:.8rem .9rem;
  border-radius:12px;border:2px solid var(--line);background:var(--card);color:var(--ink);font:inherit;text-align:left;cursor:pointer}
.choice .key{flex:none;display:inline-flex;align-items:center;justify-content:center;width:1.8rem;height:1.8rem;border-radius:50%;
  background:var(--brand-soft);font-weight:700;font-size:.9rem}
.choice.selected{border-color:var(--brand);box-shadow:0 0 0 2px var(--brand) inset}
.choice.correct{border-color:var(--ok-line);background:var(--ok-bg);color:var(--ok)}
.choice.correct .key{background:var(--ok-line);color:#fff}
.choice.wrong{border-color:var(--bad-line);background:var(--bad-bg);color:var(--bad)}
.choice.wrong .key{background:var(--bad-line);color:#fff}
.choice[disabled]{cursor:default}
.choice .tag{margin-left:auto;font-weight:700;font-size:.85rem;white-space:nowrap}
.feedback{border-radius:12px;padding:.9rem;margin:.4rem 0 .6rem;border:2px solid}
.feedback.ok{background:var(--ok-bg);border-color:var(--ok-line);color:var(--ok)}
.feedback.bad{background:var(--bad-bg);border-color:var(--bad-line);color:var(--bad)}
.feedback h3{margin:0 0 .3rem}
.feedback .exp{color:var(--ink)}
.source{font-size:.82rem;color:var(--muted);margin-top:.5rem}
.result{text-align:center}
.result .big{font-size:3rem;font-weight:800;margin:.2rem 0}
.pass{color:var(--ok)} .fail{color:var(--bad)}
.secscores{display:grid;grid-template-columns:1fr 1fr;gap:.6rem;margin:.6rem 0}
.review{border-top:1px solid var(--line);padding:.8rem 0}
.review:first-of-type{border-top:0}
.review img{width:90px;height:90px;object-fit:contain;float:right;margin:0 0 .4rem .6rem}
.ans-bad{color:var(--bad)} .ans-ok{color:var(--ok)}
.hist{width:100%;border-collapse:collapse;font-size:.92rem}
.hist td,.hist th{padding:.35rem .3rem;border-bottom:1px solid var(--line);text-align:left}
.note{background:var(--warn-bg);border-radius:10px;padding:.6rem .8rem;font-size:.92rem}
.loading{text-align:center;color:var(--muted);margin-top:3rem}
footer.foot{font-size:.8rem;color:var(--muted);text-align:center;margin-top:1.5rem}
footer.foot a{color:inherit}
@media (prefers-reduced-motion:reduce){*{transition:none!important;animation:none!important}}