:root{--bg: #0f1117;--bg-elev: #171a23;--bg-elev-2: #1f2430;--border: #2a3040;--text: #e6e8ee;--text-dim: #9aa3b2;--accent: #6c8cff;--accent-strong: #4f6fe8;--accent-soft: rgba(108, 140, 255, .12);--good: #34c98a;--good-bg: #133a2b;--good-text: #b9f3d8;--bad: #ff6b6b;--bad-bg: #3a1717;--bad-text: #ffc9c9;--warn: #f5a623;--skeleton: rgba(255, 255, 255, .06);--skeleton-shimmer: rgba(255, 255, 255, .12);--radius: 12px;--shadow: 0 6px 24px rgba(0, 0, 0, .35);color-scheme:dark}:root[data-theme=light]{--bg: #f4f5f9;--bg-elev: #ffffff;--bg-elev-2: #eef0f7;--border: #dbe0ec;--text: #1b2030;--text-dim: #59617a;--accent: #4f6fe8;--accent-strong: #4f46e5;--accent-soft: rgba(79, 111, 232, .1);--good: #12905f;--good-bg: #e2f6ec;--good-text: #0c6b46;--bad: #cf3b3b;--bad-bg: #fdecec;--bad-text: #a12626;--warn: #a76a08;--skeleton: rgba(20, 25, 45, .06);--skeleton-shimmer: rgba(20, 25, 45, .11);--shadow: 0 8px 28px rgba(24, 30, 55, .1);color-scheme:light}*{box-sizing:border-box}html,body,#root{height:100%}body{margin:0;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica,Arial,sans-serif;background:var(--bg);color:var(--text);line-height:1.55;-webkit-font-smoothing:antialiased}a{color:var(--accent)}:focus-visible{outline:2px solid var(--accent);outline-offset:2px}.app{max-width:1080px;margin:0 auto;padding:24px 20px 64px}.skip-link{position:absolute;left:12px;top:-48px;background:var(--accent-strong);color:#fff;padding:8px 14px;border-radius:8px;text-decoration:none;z-index:20;transition:top .15s ease}.skip-link:focus{top:12px}.app-header{display:flex;align-items:center;justify-content:space-between;gap:16px;flex-wrap:wrap;margin-bottom:8px}.brand{display:flex;align-items:center;gap:10px;flex-wrap:wrap}.brand-logo{border-radius:8px;flex:0 0 auto}.app-header h1{font-size:1.6rem;margin:0;letter-spacing:-.02em}.app-header .brand-accent{color:var(--accent)}.header-actions{display:flex;align-items:center;gap:8px}.tagline{color:var(--text-dim);margin:0 0 20px;font-size:.98rem;max-width:62ch}.backend-badge{font-size:.75rem;padding:3px 10px;border-radius:999px;border:1px solid var(--border);color:var(--text-dim);white-space:nowrap}.backend-badge.live{color:var(--good);border-color:var(--good);background:var(--good-bg)}.icon-btn{display:inline-flex;align-items:center;gap:7px;padding:8px 12px;border-radius:10px;border:1px solid var(--border);background:var(--bg-elev);color:var(--text);cursor:pointer;font-size:.9rem;font-weight:600;line-height:1}.icon-btn:hover{border-color:var(--accent);color:var(--accent)}.icon-btn svg{display:block}.icon-btn.share-btn{padding-inline:14px}@media (max-width: 460px){.icon-btn-text{display:none}.icon-btn.share-btn{padding:8px 10px}}.layout{display:grid;grid-template-columns:minmax(0,1fr);gap:24px}@media (min-width: 880px){.layout{grid-template-columns:minmax(0,1fr) 300px;align-items:start}}.card{background:var(--bg-elev);border:1px solid var(--border);border-radius:var(--radius);padding:20px;box-shadow:var(--shadow)}.card+.card{margin-top:20px}.topic-form label{display:block;font-weight:600;margin-bottom:8px}.topic-input{width:100%;font-size:1.05rem;padding:12px 14px;border-radius:10px;border:1px solid var(--border);background:var(--bg-elev-2);color:var(--text)}.topic-input:focus{outline:2px solid var(--accent);outline-offset:1px}.field-hint{margin:8px 0 0;font-size:.85rem;color:var(--text-dim)}.difficulty-row{display:flex;gap:8px;margin:16px 0;flex-wrap:wrap}.diff-btn{flex:1 1 auto;min-width:120px;padding:9px 12px;border-radius:10px;border:1px solid var(--border);background:var(--bg-elev-2);color:var(--text-dim);cursor:pointer;text-transform:capitalize;font-size:.95rem}.diff-btn:hover:not(:disabled){border-color:var(--accent)}.diff-btn[aria-pressed=true]{border-color:var(--accent);color:var(--text);background:var(--accent-soft);font-weight:600}.btn{display:inline-flex;align-items:center;gap:8px;padding:11px 18px;border-radius:10px;border:1px solid transparent;background:var(--accent-strong);color:#fff;font-weight:600;font-size:1rem;cursor:pointer}.btn:hover:not(:disabled){background:var(--accent)}.btn:disabled{opacity:.55;cursor:not-allowed}.btn.secondary{background:transparent;border-color:var(--border);color:var(--text)}.btn.secondary:hover:not(:disabled){border-color:var(--accent);background:var(--accent-soft)}.btn.small{padding:6px 12px;font-size:.85rem}.suggestions{margin-top:18px}.suggestions .label{font-size:.85rem;color:var(--text-dim);margin-bottom:10px}.chip-row{display:flex;flex-wrap:wrap;gap:8px}.chip{padding:6px 12px;border-radius:999px;border:1px solid var(--border);background:var(--bg-elev-2);color:var(--text);cursor:pointer;font-size:.85rem}.chip:hover{border-color:var(--accent);color:var(--accent)}.lesson-head{display:flex;justify-content:space-between;align-items:flex-start;gap:16px;flex-wrap:wrap}.lesson-head h2{margin:0 0 8px;font-size:1.5rem;letter-spacing:-.01em}.lesson-meta{display:flex;align-items:center;gap:10px;flex-wrap:wrap}.lesson-readtime{font-size:.8rem;color:var(--text-dim)}.pill{display:inline-block;font-size:.75rem;padding:2px 10px;border-radius:999px;background:var(--accent-soft);border:1px solid var(--border);color:var(--accent);text-transform:capitalize;font-weight:600}.summary{font-size:1.08rem;color:var(--text);margin:16px 0 6px}.objectives-block{margin-top:18px;padding:14px 16px;background:var(--bg-elev-2);border:1px solid var(--border);border-radius:10px}.objectives-title{margin:0 0 6px;font-size:.82rem;text-transform:uppercase;letter-spacing:.08em;color:var(--accent)}.objectives{margin:0;padding-left:22px}.objectives li{margin:4px 0}.section-block h3{margin:24px 0 6px;font-size:1.15rem;color:var(--text)}.section-block p{margin:6px 0;white-space:pre-wrap}.example{margin-top:10px;padding:10px 14px;border-left:3px solid var(--accent);background:var(--bg-elev-2);border-radius:0 8px 8px 0;font-size:.95rem}.example .example-label{font-size:.72rem;text-transform:uppercase;letter-spacing:.08em;color:var(--text-dim);display:block;margin-bottom:2px}.further-title{margin:0 0 4px}.further-hint{margin:0 0 12px;font-size:.88rem;color:var(--text-dim)}.quiz-head{display:flex;align-items:baseline;justify-content:space-between;gap:12px;flex-wrap:wrap}.quiz-head h2{margin:0}.quiz-progress{font-size:.82rem;color:var(--text-dim)}.quiz-q{margin:18px 0 0;padding:18px 0 0;border:none;border-top:1px solid var(--border)}.quiz-q:first-of-type{border-top:none;padding-top:6px}.quiz-q .q-text{font-weight:600;margin-bottom:10px;padding:0}.option{display:flex;align-items:center;gap:10px;width:100%;text-align:left;padding:10px 14px;margin:6px 0;border-radius:10px;border:1px solid var(--border);background:var(--bg-elev-2);color:var(--text);cursor:pointer;font-size:.97rem}.option:hover{border-color:var(--accent)}.option-radio{position:absolute;opacity:0;width:1px;height:1px}.option.selected{border-color:var(--accent);background:var(--accent-soft)}.option.correct{border-color:var(--good);background:var(--good-bg);color:var(--good-text);cursor:default}.option.incorrect{border-color:var(--bad);background:var(--bad-bg);color:var(--bad-text);cursor:default}.option:has(.option-radio:disabled){cursor:default}.option:has(.option-radio:focus-visible){outline:2px solid var(--accent);outline-offset:2px}.option .marker{flex:0 0 auto;font-weight:700;width:1.3em}.option-text{flex:1 1 auto}.option-tag{flex:0 0 auto;font-size:.72rem;font-weight:700;text-transform:uppercase;letter-spacing:.04em;opacity:.85}.explanation{margin-top:8px;font-size:.9rem;color:var(--text-dim)}.quiz-result{margin-top:18px;padding:16px;border-radius:10px;text-align:center;font-size:1.1rem;font-weight:600;border:1px solid var(--border);background:var(--bg-elev-2)}.quiz-result.pass{border-color:var(--good);background:var(--good-bg);color:var(--good-text)}.actions-row{display:flex;gap:10px;margin-top:20px;flex-wrap:wrap}.further .chip-row{margin-top:8px}.sidebar h3{margin:0 0 12px;font-size:1.05rem}.stats-grid{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin-bottom:16px}.stat{background:var(--bg-elev-2);border:1px solid var(--border);border-radius:10px;padding:10px 12px}.stat .value{font-size:1.4rem;font-weight:700}.stat .label{font-size:.75rem;color:var(--text-dim)}.history{list-style:none;margin:0;padding:0;max-height:360px;overflow-y:auto}.history li{padding:10px 0;border-bottom:1px solid var(--border)}.history li:last-child{border-bottom:none}.history .h-topic{font-weight:600;word-break:break-word}.history .h-meta{font-size:.78rem;color:var(--text-dim);display:flex;justify-content:space-between;gap:8px;margin-top:2px}.history .score{font-weight:600}.history .score.high{color:var(--good)}.history .score.low{color:var(--warn)}.empty{color:var(--text-dim);font-size:.9rem}.error-box{margin-top:16px;padding:12px 14px;border-radius:10px;border:1px solid var(--bad);background:var(--bad-bg);color:var(--bad-text);font-size:.92rem}.loading{display:flex;align-items:center;gap:12px;color:var(--text-dim)}.spinner{width:18px;height:18px;border:2px solid var(--border);border-top-color:var(--accent);border-radius:50%;animation:spin .8s linear infinite;flex:0 0 auto}@keyframes spin{to{transform:rotate(360deg)}}.skeleton-block{margin-top:18px;display:flex;flex-direction:column;gap:12px}.skeleton{border-radius:6px;background:linear-gradient(90deg,var(--skeleton) 25%,var(--skeleton-shimmer) 37%,var(--skeleton) 63%);background-size:400% 100%;animation:shimmer 1.4s ease infinite}.skeleton.line{height:12px}.skeleton.w-40{width:40%}.skeleton.w-60{width:60%}.skeleton.w-80{width:80%}.skeleton.w-90{width:90%}@keyframes shimmer{0%{background-position:100% 0}to{background-position:0 0}}.app-footer{margin-top:40px;text-align:center;color:var(--text-dim);font-size:.82rem}.app-footer p{margin:6px 0;max-width:64ch;margin-inline:auto}.footer-meta{opacity:.8}@media (prefers-reduced-motion: reduce){*{animation-duration:.001ms!important;animation-iteration-count:1!important;transition-duration:.001ms!important}}