@import url('https://cdn.jsdelivr.net/npm/geist@1.0.0/dist/fonts/geist-sans/style.css');
*{box-sizing:border-box}html{scroll-behavior:smooth}html,body{margin:0;background:#000;color:#e5e5e5;font-family:'Geist Sans',Geist,Inter,-apple-system,BlinkMacSystemFont,sans-serif;font-size:15px;line-height:1.65;-webkit-font-smoothing:antialiased;letter-spacing:-0.01em}
.layout{display:flex;min-height:100vh}
.sidebar{width:260px;min-width:260px;border-right:1px solid #1a1a1a;padding:28px 20px;position:sticky;top:0;height:100vh;overflow:auto;background:#000}
.brand a{color:#fff;text-decoration:none;font-weight:600;font-size:14px;letter-spacing:-.01em}
.label{margin-top:28px;color:#555;font-size:10px;letter-spacing:.12em;font-weight:600}
nav{margin-top:14px;display:flex;flex-direction:column;gap:2px}
nav a{color:#888;text-decoration:none;font-size:13px;line-height:1.4;padding:6px 8px;border-radius:6px;transition:all .15s}
nav a:hover{color:#fff;background:#111}
nav a.active{color:#fff;background:#1a1a1a}
.main{flex:1;min-width:0;max-width:760px;margin:0;padding:48px 40px 80px}
.topbar{display:flex;justify-content:flex-end;gap:10px;margin-bottom:32px;position:sticky;top:0;padding:12px 0;background:rgba(0,0,0,.85);backdrop-filter:blur(8px);z-index:10}
.download{background:#fff;color:#000;border:none;padding:7px 16px;border-radius:999px;text-decoration:none;font-size:13px;font-weight:500}
.download:hover{background:#e5e5e5}
#theme{background:#1a1a1a;border:1px solid #262626;color:#fff;border-radius:999px;padding:7px 12px;cursor:pointer;font-size:13px}
#theme:hover{background:#222}
.content h1{font-size:30px;font-weight:700;letter-spacing:-.03em;line-height:1.15;margin:0 0 12px;color:#fff}
.content h1+p{color:#999;font-size:15px;line-height:1.6;margin-bottom:8px}
.content h2{font-size:22px;font-weight:700;letter-spacing:-.02em;margin:56px 0 0;padding-top:28px;border-top:1px solid #1a1a1a;color:#fff}
.content h3{font-size:15px;font-weight:600;margin:32px 0 12px;color:#fff;letter-spacing:-.01em}
.content p{color:#999;line-height:1.7;font-size:14.5px}
.content ul.toc{list-style:none;padding:0;margin:16px 0;display:grid;gap:6px}
.content ul.toc li a{color:#888;text-decoration:none;font-size:14px;padding:4px 0;display:block}
.content ul.toc li a:hover{color:#fff}
.content ul.lessons{list-style:none;padding:0;margin:0}
.content ul.lessons li{background:#0a0a0a;border:1px solid #1e1e1e;border-radius:12px;padding:18px 20px;margin:14px 0;line-height:1.65;color:#bbb;font-size:14.5px;transition:border .15s}
.content ul.lessons li:hover{border-color:#2a2a2a}
.content ul.lessons li strong{color:#fff;font-weight:600}
.content ul.lessons li a{color:#6ea8ff;text-decoration:none}
.content ul.toc li a{color:#888}
hr{border:none;border-top:1px solid #1a1a1a;margin:48px 0}
@media(max-width:900px){.sidebar{display:none}.main{padding:24px 20px;max-width:100%}}