:root{--purple:#473985;--purple2:#5b4aa8;--bg:#f5f4fa;--card:#fff;--border:#e3e0ef;--ink:#222;--muted:#6b6b7b;--correct:#1a7f37;}
*{box-sizing:border-box}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;background:var(--bg);color:var(--ink);line-height:1.55}
.wrap{max-width:900px;margin:0 auto;padding:24px 16px 80px}
header.top{background:var(--purple);color:#fff;padding:28px 16px;text-align:center}
header.top h1{margin:0;font-size:1.6rem}
header.top p{margin:8px 0 0;opacity:.9;font-size:.95rem}
a.back{display:inline-block;margin:18px 0 4px;color:var(--purple);font-weight:600;text-decoration:none}
a.back:hover{text-decoration:underline}
h2.group-title{font-size:1.4rem;margin:8px 0 2px}
p.group-desc{color:var(--muted);margin:0 0 20px}
.q{background:var(--card);border:1px solid var(--border);border-radius:12px;padding:18px 18px 14px;margin:0 0 18px}
.q .tag{font-size:.8rem;color:var(--purple2);font-weight:700;letter-spacing:.02em;text-transform:uppercase;margin-bottom:6px}
.q .text{font-size:1.02rem;margin:0 0 12px}
.q .text p{margin:0 0 10px}
ol.choices{list-style:none;margin:0 0 10px;padding:0}
ol.choices li{display:flex;gap:10px;padding:8px 10px;border-radius:8px;margin:2px 0;align-items:baseline}
ol.choices li .lbl{font-weight:700;color:var(--purple2);min-width:22px}
ol.choices li .ans{flex:1;min-width:0}
ol.choices li .ans p{margin:0}
ol.choices li .ans table{margin:6px 0}
.q.revealed ol.choices li.correct{background:#e8f7ec;border:1px solid #bfe3c9}
.answer{display:none;margin-top:6px;font-size:.9rem;color:var(--correct);font-weight:700}
.q.revealed .answer{display:block}
button.reveal{margin-top:12px;padding:8px 14px;font-size:.85rem;font-weight:700;color:#fff;background:var(--purple2);border:none;border-radius:8px;cursor:pointer}
button.reveal:hover{background:var(--purple)}
table{border-collapse:collapse;margin:12px 0;background:#fff;box-shadow:0 1px 3px rgba(71,57,133,.08)}
table th,table td{border:1px solid #c9c3e0;padding:7px 14px;text-align:center;font-size:.95rem}
table th{background:var(--purple);color:#fff;font-weight:700}
table tbody tr:nth-child(even) td{background:#f6f4fb}
.index-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:14px;margin-top:6px}
.card{background:var(--card);border:1px solid var(--border);border-radius:12px;padding:16px;text-decoration:none;color:inherit;display:block;transition:.15s}
.card:hover{border-color:var(--purple2);box-shadow:0 4px 14px rgba(71,57,133,.12)}
.card h3{margin:0 0 6px;color:var(--purple);font-size:1.05rem}
.card p{margin:0 0 10px;color:var(--muted);font-size:.88rem}
.card .count{font-size:.85rem;font-weight:700;color:var(--purple2)}
.badge{display:inline-block;font-size:.72rem;font-weight:700;color:#fff;padding:2px 8px;border-radius:20px;vertical-align:middle}
.meta{color:var(--muted);font-size:.9rem;margin:6px 0 0}
.formulas{margin:0 0 24px}
.formula{background:var(--card);border:1px solid var(--border);border-radius:10px;padding:10px 14px;margin:0 0 8px;display:flex;align-items:center;gap:14px;flex-wrap:wrap}
.formula .flabel{font-weight:700;color:var(--purple2);min-width:150px;flex-shrink:0}
.formula span:last-child{flex:1;min-width:200px}
footer{text-align:center;color:var(--muted);font-size:.85rem;margin-top:30px}