:root{color-scheme:light dark;font-family:system-ui,-apple-system,Segoe UI,Roboto,sans-serif}*{box-sizing:border-box}body{margin:0;background:#0f1115;color:#e8eaed}.app{max-width:480px;margin:0 auto;min-height:100vh;display:flex;flex-direction:column}.screen{flex:1;padding:24px 20px 16px}.screen h1{font-size:1.4rem;margin:0 0 16px}.muted{color:#9aa0a6;font-size:.95rem}.btn{display:inline-block;border:none;border-radius:12px;padding:14px 20px;font-size:1rem;font-weight:600;background:#3b82f6;color:#fff;cursor:pointer;text-decoration:none}.btn:active{opacity:.85}.status-card{margin-top:20px;padding:14px 16px;border-radius:12px;background:#1a1d23;border:1px solid #2a2e36;font-size:.95rem}.status-ok{color:#34d399}.status-loading{color:#fbbf24}.status-error{color:#f87171}.navbar{display:flex;gap:4px;padding:8px;border-top:1px solid #2a2e36;background:#14171c;position:sticky;bottom:0}.navbar a{flex:1;text-align:center;padding:10px 4px;border-radius:10px;text-decoration:none;color:#9aa0a6;font-size:.8rem}.navbar a.active{background:#20242b;color:#e8eaed}.lesson-head{display:flex;justify-content:space-between;margin-bottom:16px}.instruction{color:#9aa0a6;margin:0 0 6px;font-size:.95rem}.stem{font-size:1.5rem;font-weight:700;margin:0 0 20px}.input{width:100%;padding:12px 14px;border-radius:10px;border:1px solid #2a2e36;background:#1a1d23;color:#e8eaed;font-size:1rem}.options{display:flex;flex-direction:column;gap:10px}.option-btn{text-align:left;padding:14px 16px;border-radius:12px;border:1px solid #2a2e36;background:#1a1d23;color:#e8eaed;font-size:1rem;cursor:pointer}.option-btn:hover:not(:disabled){border-color:#3b82f6}.option-btn:disabled{opacity:.6;cursor:default}.text-answer{display:flex;flex-direction:column;gap:12px}.feedback{display:flex;flex-direction:column}.verdict{font-size:1.2rem;font-weight:700;margin-bottom:10px}.verdict-correct{color:#34d399}.verdict-typo{color:#fbbf24}.verdict-wrong{color:#f87171}.correct-answer{padding:12px 14px;border-radius:10px;background:#1a1d23;border:1px solid #2a2e36}.result-score{text-align:center;margin:24px 0}.result-score-big{font-size:3rem;font-weight:800;color:#3b82f6}.result-rows{display:flex;flex-direction:column;gap:2px}.result-row{display:flex;justify-content:space-between;padding:12px 14px;border-radius:10px;background:#1a1d23;border:1px solid #2a2e36}