:root{--bg: #0f172a;--surface: #172038;--surface-2: #1e2a4a;--text: #e6ebf5;--muted: #93a0b8;--accent: #38bdf8;--accent-strong: #0ea5e9;--ok: #22c55e;--danger: #f87171;--radius: 14px}*{box-sizing:border-box}html,body{height:100%}body{margin:0;background:var(--bg);color:var(--text);font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;-webkit-font-smoothing:antialiased}.app-shell{min-height:100dvh;display:flex;flex-direction:column;padding-top:env(safe-area-inset-top);padding-bottom:env(safe-area-inset-bottom)}.app-header{padding:14px 16px;border-bottom:1px solid rgba(255,255,255,.08);position:sticky;top:0;background:#0f172ae6;-webkit-backdrop-filter:blur(6px);backdrop-filter:blur(6px);z-index:10}.brand{color:var(--text);text-decoration:none;font-weight:700;font-size:1.1rem}.app-main{flex:1;padding:16px;max-width:720px;width:100%;margin:0 auto}h1{font-size:1.4rem;margin:8px 0}h2{font-size:1.1rem;margin:20px 0 10px;color:var(--muted)}.muted{color:var(--muted)}.small{font-size:.85rem}.back-link{color:var(--accent);text-decoration:none;display:inline-block;margin-bottom:10px;font-size:.9rem}.stats-row{display:grid;grid-template-columns:repeat(3,1fr);gap:8px;margin:12px 0 20px}.stat-card{background:var(--surface);border-radius:var(--radius);padding:12px 8px;text-align:center}.stat-value{display:block;font-size:1.3rem;font-weight:700}.stat-label{display:block;font-size:.75rem;color:var(--muted);margin-top:2px}.course-grid{display:grid;gap:10px}.course-card{display:flex;gap:12px;background:var(--surface);border-radius:var(--radius);padding:14px;text-decoration:none;color:var(--text);align-items:flex-start}.course-card-icon{font-size:1.8rem}.course-card-body{flex:1;min-width:0}.course-card-body h3{margin:0 0 4px;font-size:1rem}.course-card-body p{margin:0 0 8px;font-size:.85rem}.progress-bar{height:8px;background:var(--surface-2);border-radius:999px;overflow:hidden;margin:8px 0 6px}.progress-bar-fill{height:100%;background:linear-gradient(90deg,var(--accent),var(--accent-strong));transition:width .3s ease}.chapter-list{list-style:none;padding:0;margin:20px 0;background:var(--surface);border-radius:var(--radius);overflow:hidden}.chapter-list li+li{border-top:1px solid rgba(255,255,255,.06)}.chapter-list a{display:flex;align-items:center;gap:8px;padding:14px;color:var(--text);text-decoration:none}.tag{font-size:.7rem;background:var(--surface-2);color:var(--accent);padding:2px 6px;border-radius:999px}.btn{display:inline-flex;align-items:center;justify-content:center;gap:6px;padding:12px 18px;border-radius:999px;border:1px solid rgba(255,255,255,.15);background:var(--surface);color:var(--text);font-size:.95rem;text-decoration:none;cursor:pointer;margin:6px 6px 6px 0;-webkit-tap-highlight-color:transparent}.btn-primary{background:var(--accent-strong);border-color:transparent;color:#04141f;font-weight:700}.btn-cert{background:#a16207;border-color:transparent;color:#fff7e6}.btn:disabled{opacity:.5;cursor:not-allowed}.chapter-content{background:var(--surface);border-radius:var(--radius);padding:18px;line-height:1.6}.chapter-content pre{background:#0b1226;padding:12px;border-radius:10px;overflow-x:auto}.chapter-content code{background:#0b1226;padding:2px 5px;border-radius:4px;font-size:.9em}.chapter-content pre code{background:none;padding:0}.chapter-nav{display:flex;justify-content:space-between;align-items:center;margin-top:18px}.quiz-block{margin-top:20px;background:var(--surface);border-radius:var(--radius);padding:18px}.quiz-question{border:none;padding:0;margin:0 0 18px}.quiz-question legend{font-weight:600;margin-bottom:8px;padding:0}.quiz-option{display:flex;align-items:center;gap:10px;padding:10px 12px;border-radius:10px;background:var(--surface-2);margin-bottom:6px}.quiz-option--checked{outline:2px solid var(--accent)}.quiz-option--correct{outline:2px solid var(--ok)}.quiz-option--wrong{outline:2px solid var(--danger)}.quiz-explanation{font-size:.85rem;color:var(--muted);margin-top:-6px}.quiz-result{display:flex;align-items:center;gap:12px;margin-top:10px}.quiz-result--pass{color:var(--ok)}.quiz-result--fail{color:var(--danger)}.certificate{margin-top:40px;text-align:center;background:linear-gradient(160deg,var(--surface),var(--surface-2));border-radius:var(--radius);padding:40px 20px;border:1px solid rgba(255,255,255,.1)}.certificate-badge{font-size:3rem}.certificate-course{font-size:1.2rem;font-weight:700;margin:10px 0 4px}@media (min-width: 640px){.course-grid{grid-template-columns:1fr 1fr}}