:root{--bg: #0f1115;--panel: #171a21;--panel-2: #1f232d;--text: #e8eaed;--muted: #9aa0aa;--border: #2a2f3a;--accent: #6ea8fe;--accent-ink: #0b1220;--correct: #2f9e57;--wrong: #d9534f;--radius: 14px}@media (prefers-color-scheme: light){:root{--bg: #f6f7f9;--panel: #ffffff;--panel-2: #f0f2f5;--text: #1a1d23;--muted: #5b616e;--border: #e2e5ea;--accent: #2563eb;--accent-ink: #ffffff}}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--text);font:16px/1.5 system-ui,-apple-system,Segoe UI,Roboto,sans-serif}.app{max-width:720px;margin:0 auto;padding:24px 16px 64px}header h1{margin:0 0 4px;font-size:1.6rem}.muted{color:var(--muted)}.input-card,.panel{background:var(--panel);border:1px solid var(--border);border-radius:var(--radius);padding:16px;margin-top:16px}textarea{width:100%;background:var(--panel-2);color:var(--text);border:1px solid var(--border);border-radius:10px;padding:12px;font:inherit;resize:vertical}.btn-row{display:flex;gap:8px;flex-wrap:wrap;margin-top:12px}.btn{background:var(--panel-2);color:var(--text);border:1px solid var(--border);border-radius:10px;padding:10px 14px;font:inherit;cursor:pointer}.btn:hover:not(:disabled){border-color:var(--accent)}.btn:disabled{opacity:.5;cursor:not-allowed}.btn-primary{background:var(--accent);color:var(--accent-ink);border-color:var(--accent);font-weight:600}.panel.error{border-color:var(--wrong)}.panel h2{margin-top:4px}.tabs{display:flex;gap:8px;margin:12px 0 16px}.tab{flex:1;padding:10px;background:var(--panel-2);border:1px solid var(--border);border-radius:10px;color:var(--muted);font:inherit;cursor:pointer}.tab.active{color:var(--text);border-color:var(--accent)}.skeleton .bar{height:14px;border-radius:6px;background:linear-gradient(90deg,var(--panel-2),var(--border),var(--panel-2));background-size:200% 100%;animation:shimmer 1.3s infinite;margin-bottom:10px}.skeleton .bar.short{width:55%}@keyframes shimmer{0%{background-position:200% 0}to{background-position:-200% 0}}.progress-row{margin-bottom:10px}.card{width:100%;border:none;background:transparent;color:var(--text);padding:0;cursor:pointer;perspective:1200px}.card-inner{position:relative;width:100%;min-height:180px;transition:transform .5s;transform-style:preserve-3d}.card.is-flipped .card-inner{transform:rotateY(180deg)}.card-face{position:absolute;top:0;right:0;bottom:0;left:0;-webkit-backface-visibility:hidden;backface-visibility:hidden;background:var(--panel-2);border:1px solid var(--border);border-radius:12px;padding:20px;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:10px;text-align:center}.card-face p{margin:0;font-size:1.1rem;color:var(--text)}.card-front{transform:rotateY(0)}.card-back{transform:rotateY(180deg)}.card-hint{font-size:.75rem;text-transform:uppercase;letter-spacing:.05em}.question{font-size:1.1rem;font-weight:600}.options{display:flex;flex-direction:column;gap:8px}.option{text-align:left;padding:12px;background:var(--panel-2);border:1px solid var(--border);border-radius:10px;color:var(--text);font:inherit;cursor:pointer}.option:hover:not(:disabled){border-color:var(--accent)}.option:disabled{cursor:default}.option.correct{border-color:var(--correct);background:color-mix(in srgb,var(--correct) 18%,var(--panel-2))}.option.wrong{border-color:var(--wrong);background:color-mix(in srgb,var(--wrong) 18%,var(--panel-2))}.explanation{margin-top:12px;padding:12px;background:var(--panel-2);border-left:3px solid var(--accent);border-radius:6px}.quiz-results h3{margin-top:0}footer{margin-top:24px;font-size:.85rem;text-align:center}