:root{--bg:#0f1222;--surface:#131a33;--surface2:#0f1530;--text:#e8ecff;--muted:#b7c0ff;--brand:#7aa2ff;--line:rgba(255,255,255,.12)}
*{box-sizing:border-box}html,body{margin:0;padding:0}
body{font-family:Inter,system-ui,Arial,sans-serif;background:linear-gradient(180deg,#0b1020,#0f1222);color:var(--text);line-height:1.6}
.container{max-width:1180px;margin:0 auto;padding:24px 16px 64px}
.header{position:sticky;top:0;background:#0d1228cc;backdrop-filter:blur(6px);border-bottom:1px solid var(--line);z-index:60}
.nav{display:flex;align-items:center;justify-content:space-between;gap:10px;max-width:1180px;margin:0 auto;padding:10px 16px}
.brand{display:flex;gap:8px;align-items:center;font-weight:800}
.brand img{width:28px;height:28px}
.burger{display:none;background:none;border:1px solid var(--line);color:#e8ecff;padding:8px 10px;border-radius:10px}
.nav-links{display:flex;gap:10px;align-items:center}
.nav-links a{color:#dbe2ff;text-decoration:none;padding:8px 10px;border-radius:10px;border:1px solid transparent}
.nav-links a:hover{background:#11183b;border-color:var(--line)}
.cta{background:var(--brand);color:#0b1020;font-weight:700;border:1px solid rgba(0,0,0,.2)}
@media(max-width:860px){.burger{display:block}.nav-links{display:none;position:absolute;top:58px;left:0;right:0;background:#0d1228ee;padding:12px 16px;border-bottom:1px solid var(--line)}.nav-links.open{display:flex;flex-direction:column;align-items:flex-start}}
.hero{background:radial-gradient(1000px 300px at 10% -20%,rgba(122,162,255,.15),transparent 60%),radial-gradient(1000px 300px at 100% 0%,rgba(85,214,190,.08),transparent 60%);border:1px solid var(--line);border-radius:18px;padding:22px;margin-top:14px;box-shadow:0 20px 60px rgba(0,0,0,.35)}
.hero h1{margin:0 0 6px;font-size:clamp(22px,3.2vw,40px)}.hero .lead{margin:4px 0 10px;color:var(--muted)}
.badges{display:flex;gap:8px;flex-wrap:wrap}.badge{display:inline-flex;align-items:center;gap:6px;padding:8px 12px;border-radius:999px;background:#1a244e;border:1px solid var(--line);color:#dbe2ff;font-size:.9rem}
.grid{display:grid;grid-template-columns:repeat(12,1fr);gap:16px;margin-top:18px}
.card{grid-column:span 12;background:linear-gradient(180deg,var(--surface),var(--surface2));border:1px solid var(--line);border-radius:18px;padding:16px;box-shadow:0 12px 30px rgba(0,0,0,.35)}
@media(min-width:680px){.card{grid-column:span 6}}@media(min-width:980px){.card{grid-column:span 4}}
.card h3{margin:0 0 6px;font-size:1.12rem}.card p{margin:0 0 10px;color:#b7c0ff}.actions{display:flex;gap:10px;flex-wrap:wrap}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:10px 14px;border-radius:12px;text-decoration:none;background:var(--brand);color:#0b1020;font-weight:700;border:1px solid rgba(0,0,0,.2)}
.btn.secondary{background:#1b2750;color:#e6ecff;border:1px solid var(--line)}
.layout{display:grid;gap:16px;grid-template-columns:1fr}
@media(min-width:1100px){.layout{grid-template-columns:280px 1fr}}
.toc-toggle{display:inline-block;background:#1b2750;color:#e6ecff;border:1px solid var(--line);padding:8px 12px;border-radius:10px;margin:6px 0}
.toc{display:none;background:linear-gradient(180deg,#0f1530,#0d1433);border:1px solid var(--line);border-radius:14px;padding:12px}
.toc.open{display:block}@media(min-width:1100px){.toc{display:block;position:sticky;top:80px;max-height:calc(100vh - 120px);overflow:auto}}
.toc a{display:block;padding:8px 10px;border-radius:8px;color:#c5d2ff;text-decoration:none;border:1px solid transparent}
.toc a:hover{background:#121a36;border-color:var(--line)}.toc .minor{padding-left:22px;font-size:.95rem;color:#9fb2ff}
.subject{background:linear-gradient(180deg,var(--surface),#0e1633);border:1px solid var(--line);border-radius:16px;padding:16px;margin-top:14px}
.lesson-grid{display:grid;grid-template-columns:repeat(12,1fr);gap:12px;margin:10px 0 4px}
.lesson-card{grid-column:span 12;background:#0b132b;border:1px solid var(--line);border-radius:12px;padding:10px 12px;text-decoration:none;color:#e8ecff;display:flex;gap:10px;align-items:center}
.lesson-num{min-width:34px;height:34px;border-radius:10px;background:#1b2750;display:flex;align-items:center;justify-content:center;font-weight:800}
.lesson-title{flex:1}@media(min-width:680px){.lesson-card{grid-column:span 6}}@media(min-width:980px){.lesson-card{grid-column:span 4}}
.footer{border-top:1px solid var(--line);margin-top:26px}.footer .inner{max-width:1180px;margin:0 auto;padding:16px;color:#9fb2ff;display:flex;flex-wrap:wrap;gap:12px;justify-content:space-between}
.footer a{color:#bcd2ff;text-decoration:none}.footer a:hover{text-decoration:underline}