:root{--navy:#071426;--navy-2:#0c2038;--ink:#152333;--muted:#6d7c8e;--line:#dce4ec;--bg:#f4f7fa;--blue:#1b6ef3;--blue-soft:#eaf2ff;--green:#15966d;--red:#d94b4b;--gold:#e3a62f;--radius:8px}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",sans-serif}.app-shell{min-height:100vh}.topbar{height:72px;background:var(--navy);color:#fff;display:flex;align-items:center;justify-content:space-between;padding:0 36px}.brand{display:flex;align-items:center;gap:12px}.brand-mark{display:grid;place-items:center;width:34px;height:34px;border:1px solid #8ca3bd;color:#dbe8f6;font-size:15px}.brand strong{display:block;font-size:17px;font-weight:650;letter-spacing:0}.brand small{display:block;color:#9aadc1;font-size:11px;margin-top:3px}.top-actions{display:flex;align-items:center;gap:18px}.save-status{font-size:12px;color:#9dc3af}.ghost-btn,.outline-btn,.nav-btn,.icon-btn{border:1px solid 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rgba(22,48,78,.04)}.question-top{display:flex;align-items:center;gap:10px}.type-badge{font-size:11px;color:var(--blue);background:var(--blue-soft);padding:5px 9px;border-radius:4px;font-weight:700}.question-number{font-size:12px;color:var(--muted)}.star-btn{margin-left:auto;border:0;background:transparent;color:#a2afbc;font-size:26px;line-height:1;cursor:pointer;padding:2px 3px}.star-btn.starred{color:var(--gold)}.question-card h2{font-size:20px;line-height:1.7;font-weight:600;margin:25px 0 24px;white-space:pre-wrap}.options{display:grid;gap:10px}.option{display:flex;align-items:flex-start;gap:12px;border:1px solid var(--line);border-radius:6px;padding:13px 15px;text-align:left;background:#fff;color:var(--ink);font-size:14px;line-height:1.5;cursor:pointer;transition:.15s}.option:hover{border-color:#90b5ed;background:#fafcff}.option.selected{border-color:var(--blue);background:var(--blue-soft)}.option.correct{border-color:#72c5a7;background:#effaf5}.option.incorrect{border-color:#efaaa5;background:#fff4f3}.option-key{display:grid;place-items:center;flex:0 0 24px;height:24px;border:1px solid #c7d2de;border-radius:50%;font-size:12px;color:#617286}.option.selected .option-key{border-color:var(--blue);background:var(--blue);color:#fff}.option.correct .option-key{border-color:var(--green);background:var(--green);color:#fff}.option.incorrect .option-key{border-color:var(--red);background:var(--red);color:#fff}.feedback{margin-top:18px;padding:13px 15px;background:#f7fafc;border-left:3px solid var(--blue);font-size:13px;line-height:1.7;color:#4f6275}.feedback 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.option:disabled{cursor:not-allowed;opacity:.9}