:root{--bg:#f4f7fb;--panel:#fff;--ink:#172033;--muted:#687386;--line:#dce3ec;--accent:#2f67d8;--accent2:#e9f0ff;--good:#137a52;--goodbg:#eaf8f2;--bad:#b33a3a;--badbg:#fff0f0;--shadow:0 16px 44px rgba(30,50,85,.09)}
*{box-sizing:border-box}body{margin:0;font-family:Inter,ui-sans-serif,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;background:var(--bg);color:var(--ink)}button,select{font:inherit}.topbar{height:64px;display:flex;align-items:center;justify-content:space-between;padding:0 24px;background:#fff;border-bottom:1px solid var(--line);position:sticky;top:0;z-index:20}.brand{display:flex;gap:12px;align-items:center;font-weight:800}.brand-mark{width:36px;height:36px;border-radius:10px;background:#15213c;color:#fff;display:grid;place-items:center}.brand small{display:block;color:var(--muted);font-weight:500;font-size:11px}.top-actions{display:flex;gap:8px}.top-actions button,.back-home{border:1px solid var(--line);background:#fff;border-radius:9px;padding:8px 12px;cursor:pointer}.hero{max-width:920px;margin:58px auto 28px;padding:0 24px}.eyebrow{text-transform:uppercase;letter-spacing:.12em;color:var(--accent);font-size:12px;font-weight:800}.hero h1{font-size:44px;margin:8px 0 10px}.hero p{font-size:17px;line-height:1.7;color:var(--muted);max-width:760px}.subject-grid{max-width:920px;margin:0 auto;padding:0 24px 60px;display:grid;grid-template-columns:repeat(3,1fr);gap:18px}.subject-card{background:#fff;border:1px solid var(--line);border-radius:18px;padding:24px;min-height:230px;box-shadow:var(--shadow);cursor:pointer;display:flex;flex-direction:column;gap:14px}.subject-card:hover{transform:translateY(-2px)}.subject-card.disabled{opacity:.48;cursor:default}.subject-icon{font-size:30px}.subject-card h2{margin:0;font-size:22px}.subject-card p{color:var(--muted);line-height:1.5;flex:1}.subject-meta{font-weight:700;color:var(--accent)}.shell{display:grid;grid-template-columns:280px minmax(0,1fr);min-height:calc(100vh - 64px)}.sidebar{background:#fff;border-right:1px solid var(--line);padding:22px 18px;position:sticky;top:64px;height:calc(100vh - 64px);overflow:auto}.back-home{margin-bottom:18px}.side-title{font-size:20px;font-weight:800;margin-bottom:22px}.filter-label{text-transform:uppercase;letter-spacing:.1em;font-size:10px;color:var(--muted);font-weight:800;margin:18px 0 9px}.pill-row{display:flex;flex-wrap:wrap;gap:7px}.pill,.topic{border:1px solid var(--line);background:#fff;border-radius:10px;padding:9px 10px;cursor:pointer;color:#39465a}.pill.active,.topic.active{background:var(--accent2);border-color:#a9c0f4;color:#1e55bf;font-weight:700}.topic-list{display:grid;gap:8px}.topic{text-align:left}.content{padding:28px;min-width:0}.practice-card{max-width:940px;margin:0 auto;background:#fff;border:1px solid var(--line);border-radius:18px;box-shadow:var(--shadow);overflow:hidden}.practice-head{padding:18px 24px;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;gap:15px}.crumb{font-weight:800}.crumb span{color:#a6afbd;margin:0 5px}.subcrumb{margin-top:5px;color:var(--muted);font-size:12px}.practice-head select{border:1px solid var(--line);border-radius:9px;padding:8px 10px;background:#fff}.question-area{padding:30px 40px 26px}.question-number{width:34px;height:34px;border-radius:50%;background:var(--accent2);color:var(--accent);font-weight:800;display:grid;place-items:center;margin-bottom:16px}.question-stem{font-size:24px;line-height:1.45;margin:0 0 22px}.passage{background:#f8fafc;border:1px solid var(--line);border-radius:13px;padding:18px 20px;margin:0 0 22px;line-height:1.65}.passage h3{margin:0 0 10px}.passage p{margin:7px 0}.visual-box,.choice-strip-wrap{margin:18px auto 24px;max-width:720px;text-align:center}.visual-box img,.choice-strip{display:block;max-width:100%;max-height:430px;margin:auto;object-fit:contain;border-radius:10px}.choice-strip-labels{display:grid;grid-auto-flow:column;grid-auto-columns:1fr;gap:8px;margin-top:8px;font-weight:800;color:var(--muted)}.answer-list{display:grid;gap:11px;margin-top:18px}.answer-option{width:100%;display:flex;align-items:center;gap:12px;border:1.5px solid var(--line);background:#fff;border-radius:13px;padding:14px 16px;cursor:pointer;text-align:left}.answer-option:hover:not(:disabled){border-color:#9bb6ef;background:#fafcff}.answer-option.selected{border-color:var(--accent);background:var(--accent2)}.answer-option:disabled{cursor:default;opacity:1}.answer-option .letter{width:30px;height:30px;border-radius:50%;border:1px solid #bac5d4;display:grid;place-items:center;font-weight:800;flex:none}.answer-option.selected .letter{background:var(--accent);color:#fff;border-color:var(--accent)}.answer-option.correct-choice{border-color:#49a57d;background:#eefaf5}.answer-option.correct-choice .letter{background:var(--good);border-color:var(--good);color:#fff}.answer-option.wrong-choice{border-color:#df8585;background:#fff3f3}.answer-option.wrong-choice .letter{background:var(--bad);border-color:var(--bad);color:#fff}.answer-option img{max-width:180px;max-height:120px;object-fit:contain}.answer-text{font-size:17px;line-height:1.45}.action-row{display:flex;gap:10px;margin-top:20px}.submit-btn,.retry-btn{border:0;border-radius:10px;padding:11px 18px;font-weight:800;cursor:pointer}.submit-btn{background:var(--accent);color:#fff}.submit-btn:disabled{opacity:.4;cursor:not-allowed}.retry-btn{background:#eef2f7;color:#425066}.feedback{margin-top:22px;border-radius:13px;padding:18px 20px}.feedback.correct{background:var(--goodbg);border:1px solid #b7e4d2}.feedback.incorrect{background:var(--badbg);border:1px solid #efc6c6}.feedback-title{font-size:19px;font-weight:900;color:var(--good)}.feedback.incorrect .feedback-title{color:var(--bad)}.correct-answer{margin-top:8px}.explanation{margin-top:13px;padding-top:13px;border-top:1px solid rgba(0,0,0,.08)}.explanation span{text-transform:uppercase;letter-spacing:.08em;font-size:10px;font-weight:900;color:var(--muted)}.explanation p{margin:6px 0 0;line-height:1.6}.question-nav{border-top:1px solid var(--line);padding:15px 20px;display:flex;align-items:center;gap:12px;justify-content:space-between}.question-nav>button{border:1px solid var(--line);background:#fff;border-radius:9px;padding:9px 12px;cursor:pointer}.question-nav>button:disabled{opacity:.35}.q-dots{display:flex;gap:5px;flex-wrap:wrap;justify-content:center}.q-dot{width:30px;height:30px;border:1px solid var(--line);background:#fff;border-radius:8px;cursor:pointer;font-size:11px}.q-dot.active{border-color:var(--accent);color:var(--accent);font-weight:800}.q-dot.done{background:#eef8f4;border-color:#a9dac8}.drawer{position:fixed;inset:0;background:rgba(17,25,39,.35);display:none;justify-content:flex-end;z-index:50}.drawer.open{display:flex}.drawer-panel,.drawer-card{width:min(520px,92vw);height:100%;background:#fff;box-shadow:-12px 0 35px rgba(0,0,0,.15);padding:22px;overflow:auto}.drawer-head{display:flex;justify-content:space-between;align-items:center;margin-bottom:20px}.drawer-head button{border:0;background:#eef2f7;border-radius:8px;padding:8px 11px}.progress-row{display:flex;justify-content:space-between;padding:12px 0;border-bottom:1px solid var(--line)}.muted{color:var(--muted);font-size:12px;line-height:1.5}.empty{padding:50px;text-align:center;color:var(--muted)}
@media(max-width:800px){.topbar{height:56px;padding:0 12px}.brand small{display:none}.shell{display:block}.sidebar{position:static;height:auto;border-right:0;border-bottom:1px solid var(--line);padding:12px}.side-title{display:inline-block;margin:0 8px 8px 0}.filter-label{margin-top:10px}.topic-list{display:flex;overflow-x:auto;padding-bottom:3px}.topic{white-space:nowrap}.content{padding:12px}.practice-card{border-radius:14px}.practice-head{padding:13px 14px}.question-area{padding:20px 16px}.question-stem{font-size:20px}.answer-text{font-size:16px}.question-nav{position:sticky;bottom:0;background:#fff;z-index:4}.q-dots{max-height:68px;overflow:auto}.subject-grid{grid-template-columns:1fr}.hero{margin-top:34px}.hero h1{font-size:34px}}