:root{
  --navy:#1e3a5f; --navy2:#2c5282; --bg:#f4f6f9; --card:#fff;
  --text:#1a202c; --muted:#64748b; --line:#e2e8f0; --ok:#16a34a; --bad:#dc2626;
}
*{box-sizing:border-box;margin:0;padding:0}
body{font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  background:var(--bg);color:var(--text);line-height:1.5;-webkit-font-smoothing:antialiased}
.screen{display:none;min-height:100vh;padding:16px}
.screen.active{display:block}
.card{max-width:680px;margin:40px auto;background:var(--card);border-radius:16px;
  padding:32px;box-shadow:0 4px 24px rgba(0,0,0,.06)}
.hero{text-align:center;background:linear-gradient(135deg,var(--navy),var(--navy2));color:#fff}
.hero h1{font-size:2.2rem;font-weight:800;letter-spacing:.5px}
.subtitle{font-size:1.05rem;margin-top:8px;opacity:.92}
.desc{margin:18px 0;font-size:.95rem;opacity:.85;line-height:1.6}
h2{font-size:1.5rem;color:var(--navy);margin-bottom:20px}
label{display:block;font-size:.85rem;color:var(--muted);margin:14px 0 6px;font-weight:600}
input{width:100%;padding:12px 14px;border:1px solid var(--line);border-radius:10px;
  font-size:1rem;outline:none}
input:focus{border-color:var(--navy2)}
.btn{display:inline-block;background:var(--navy);color:#fff;border:none;border-radius:10px;
  padding:13px 22px;font-size:1rem;font-weight:600;cursor:pointer;transition:.15s;width:100%}
.btn:hover{background:var(--navy2)}
.btn.primary{margin-top:18px}
.btn.small{padding:9px 16px;font-size:.88rem;width:auto}
.btn.ghost{background:#fff;color:var(--navy);border:1px solid var(--line)}
.hint{margin-top:14px;font-size:.8rem;color:var(--muted);text-align:center}
.err{color:var(--bad);font-size:.82rem;margin-top:10px;min-height:1em}
/* Quiz */
.quiz-bar{position:sticky;top:0;background:var(--navy);color:#fff;padding:12px 16px;
  display:flex;justify-content:space-between;align-items:center;font-size:.9rem;z-index:10}
.qb-left span{margin-right:16px}
.timer{font-variant-numeric:tabular-nums;font-weight:700}
.quiz-body{max-width:720px;margin:20px auto;padding:0 8px}
.q-text{font-size:1.15rem;font-weight:600;margin-bottom:18px;line-height:1.5}
.q-options{display:flex;flex-direction:column;gap:10px}
.opt{display:flex;align-items:center;gap:12px;padding:14px 16px;border:1px solid var(--line);
  border-radius:12px;cursor:pointer;background:#fff;transition:.12s;font-size:1rem}
.opt:hover{border-color:var(--navy2)}
.opt.sel{background:#eef4fb;border-color:var(--navy2);font-weight:600}
.opt .mark{width:26px;height:26px;border-radius:50%;border:2px solid var(--line);
  display:flex;align-items:center;justify-content:center;font-size:.8rem;flex-shrink:0}
.opt.sel .mark{background:var(--navy);color:#fff;border-color:var(--navy)}
.q-nav{display:flex;justify-content:space-between;margin:22px 0}
.q-grid{display:grid;grid-template-columns:repeat(10,1fr);gap:6px;margin-top:10px}
.gcell{aspect-ratio:1;border:1px solid var(--line);border-radius:8px;display:flex;
  align-items:center;justify-content:center;font-size:.8rem;cursor:pointer;background:#fff}
.gcell.sel{background:var(--navy);color:#fff;border-color:var(--navy)}
.gcell.ans{background:#dcfce7;border-color:#16a34a}
/* Result */
.score{font-size:3rem;font-weight:800;color:var(--navy);text-align:center;margin:10px 0}
.r-detail{margin:18px 0;font-size:.95rem}
.r-detail .row{display:flex;justify-content:space-between;padding:8px 0;border-bottom:1px solid var(--line)}
.r-detail .row span:last-child{font-weight:700}
@media(max-width:520px){.q-grid{grid-template-columns:repeat(8,1fr)}.quiz-body{padding:0 4px}}
/* Review */
.rev-list{margin:18px 0;display:flex;flex-direction:column;gap:18px;max-height:62vh;overflow:auto}
.rev-item{border:1px solid var(--line);border-radius:12px;padding:14px 16px;background:#fff}
.rev-q{font-size:.98rem;line-height:1.5;margin-bottom:10px}
.rev-opts{display:flex;flex-direction:column;gap:8px}
.rev-opt{display:flex;align-items:center;gap:10px;padding:9px 12px;border:1px solid var(--line);border-radius:9px;font-size:.92rem}
.rev-opt.correct{background:#dcfce7;border-color:#16a34a}
.rev-opt.wrong{background:#fee2e2;border-color:#dc2626}
.rev-opt .mark{width:24px;height:24px;border-radius:50%;border:2px solid var(--line);display:flex;align-items:center;justify-content:center;font-size:.78rem;flex-shrink:0}
.rev-opt.correct .mark{background:#16a34a;color:#fff;border-color:#16a34a}
.rev-opt.wrong .mark{background:#dc2626;color:#fff;border-color:#dc2626}
.rev-ref{margin-top:10px;font-size:.82rem;color:#64748b;font-style:italic;border-left:3px solid var(--navy2);padding-left:10px}