*{margin:0;padding:0;box-sizing:border-box}
:root{
  --bg-dark:#0d0d0d;--bg-card:#111111;--bg-code:#161616;--bg-elevated:#1a1a1a;
  --text-primary:#e0e0e0;--text-secondary:#888;--text-muted:#484848;
  --accent:#d9d9d9;--accent-hover:#b0b0b0;
  --accent-html:#e06c75;--accent-css:#61afef;--accent-js:#e5c07b;--accent-react:#61dafb;--accent-node:#98c379;--accent-tools:#c678dd;
  --border:rgba(255,255,255,.08);--border-strong:rgba(255,255,255,.14);
  --font-sans:'Inter','Segoe UI',system-ui,-apple-system,sans-serif;
  --font-mono:'JetBrains Mono','Cascadia Code','Fira Code',Consolas,monospace;
  --radius:14px;--radius-sm:10px;--radius-xs:6px;
  --sidebar-w:280px;
}
html{scroll-behavior:smooth}
body{font-family:var(--font-sans);background:var(--bg-dark);color:var(--text-primary);overflow-x:hidden;line-height:1.6}
a{color:inherit;text-decoration:none}
::selection{background:rgba(217,217,217,.12)}

/* ═══ NAV ═══ */
.l-nav{
  position:fixed;top:0;left:0;right:0;height:56px;z-index:200;
  display:flex;align-items:center;justify-content:space-between;
  padding:0 40px;background:rgba(13,13,13,.88);backdrop-filter:blur(32px) saturate(1.4);
  border-bottom:1px solid rgba(255,255,255,.05);
}
.l-nav .logo{display:flex;align-items:center;gap:10px;font-weight:700;font-size:16px;letter-spacing:-.3px}
.l-nav .logo img{width:26px;height:26px;border-radius:7px}
.l-nav .links{display:flex;align-items:center;gap:4px}
.l-nav .links a{
  font-size:13px;color:var(--text-secondary);font-weight:500;
  padding:7px 14px;border-radius:var(--radius-xs);transition:all .2s;
}
.l-nav .links a:hover{color:var(--text-primary);background:rgba(255,255,255,.05)}
.l-nav .links a.active{color:#fff;background:rgba(255,255,255,.08)}
.l-nav .nav-btn{
  background:rgba(255,255,255,.92);color:#0d0d0d;padding:7px 20px;border-radius:var(--radius-xs);
  font-size:13px;font-weight:700;cursor:pointer;border:none;font-family:var(--font-sans);
  transition:all .25s;
}
.l-nav .nav-btn:hover{background:#fff;transform:translateY(-1px);box-shadow:0 6px 24px rgba(255,255,255,.08)}

/* ═══ HERO (index page) ═══ */
.l-hero{
  text-align:center;padding:130px 24px 56px;max-width:720px;margin:0 auto;position:relative;
}
.l-hero::before{
  content:'';position:absolute;top:40%;left:50%;transform:translate(-50%,-50%);
  width:500px;height:500px;background:radial-gradient(circle,rgba(217,217,217,.04) 0%,transparent 70%);
  pointer-events:none;
}
.l-hero h1{
  font-size:clamp(36px,5.5vw,52px);font-weight:800;letter-spacing:-2px;margin-bottom:18px;
  line-height:1.05;background:linear-gradient(180deg,#fff 30%,#888 100%);
  -webkit-background-clip:text;-webkit-text-fill-color:transparent;
}
.l-hero p{font-size:16px;color:var(--text-secondary);max-width:500px;margin:0 auto;line-height:1.75}

/* ═══ INDEX CARDS ═══ */
.l-courses{max-width:900px;margin:0 auto;padding:0 24px 60px;display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:14px}
.l-card{
  padding:28px 24px;border-radius:var(--radius);background:rgba(255,255,255,.02);
  border:1px solid var(--border);cursor:pointer;transition:all .25s;text-decoration:none;display:block;
}
.l-card:hover{border-color:var(--border-strong);background:rgba(255,255,255,.04);transform:translateY(-3px);box-shadow:0 8px 32px rgba(0,0,0,.3)}
.l-card-icon{width:44px;height:44px;border-radius:10px;display:flex;align-items:center;justify-content:center;margin-bottom:16px}
.l-card h3{font-size:17px;font-weight:700;margin-bottom:6px;color:var(--text-primary)}
.l-card p{font-size:13px;color:var(--text-secondary);line-height:1.6}
.l-card-meta{font-size:11px;color:var(--text-muted);margin-top:12px;font-weight:600;text-transform:uppercase;letter-spacing:.5px;display:block}

/* ═══ SIDEBAR LAYOUT (language pages) ═══ */
.l-layout{
  display:flex;min-height:100vh;padding-top:56px;
}
.l-sidebar{
  position:fixed;top:56px;left:0;bottom:0;width:var(--sidebar-w);
  background:rgba(13,13,13,.6);backdrop-filter:blur(16px);
  border-right:1px solid var(--border);
  display:flex;flex-direction:column;overflow:hidden;z-index:100;
}
.l-sidebar-head{
  padding:24px 20px 16px;border-bottom:1px solid var(--border);flex-shrink:0;
}
.l-sidebar-back{
  font-size:12px;color:var(--text-muted);font-weight:500;display:inline-flex;align-items:center;gap:4px;
  margin-bottom:12px;transition:color .2s;
}
.l-sidebar-back:hover{color:var(--text-secondary)}
.l-sidebar-head h2{font-size:20px;font-weight:800;letter-spacing:-.5px}
.l-sidebar-head p{font-size:12px;color:var(--text-muted);margin-top:4px}
.l-sidebar-list{
  flex:1;overflow-y:auto;padding:12px 10px;
  scrollbar-width:thin;scrollbar-color:rgba(255,255,255,.08) transparent;
}
.l-sidebar-list::-webkit-scrollbar{width:4px}
.l-sidebar-list::-webkit-scrollbar-track{background:transparent}
.l-sidebar-list::-webkit-scrollbar-thumb{background:rgba(255,255,255,.08);border-radius:4px}

.l-side-item{
  display:flex;align-items:center;gap:10px;
  padding:10px 12px;border-radius:var(--radius-xs);cursor:pointer;
  transition:all .15s;margin-bottom:2px;
}
.l-side-item:hover{background:rgba(255,255,255,.04)}
.l-side-item.on{background:rgba(255,255,255,.06)}
.l-side-item .num{
  width:24px;height:24px;border-radius:6px;display:flex;align-items:center;justify-content:center;
  font-size:10px;font-weight:700;flex-shrink:0;color:#0d0d0d;
}
.l-side-item .t{font-size:13px;font-weight:500;color:var(--text-secondary);transition:color .15s}
.l-side-item.on .t{color:var(--text-primary);font-weight:600}
.l-side-item:hover .t{color:var(--text-primary)}

/* main content area */
.l-main{
  margin-left:var(--sidebar-w);flex:1;min-width:0;
}
.l-main-inner{max-width:820px;margin:0 auto;padding:40px 48px 80px}

/* ═══ CONTENT ═══ */
.l-content-header{
  padding:0 0 28px;border-bottom:1px solid var(--border);margin-bottom:36px;
}
.l-content-header h2{font-size:30px;font-weight:800;letter-spacing:-.8px;margin-bottom:10px}
.l-content-header p{font-size:15px;color:var(--text-secondary);line-height:1.75}

.l-body h3{font-size:17px;font-weight:700;margin:36px 0 14px;color:var(--text-primary);letter-spacing:-.2px}
.l-body p{font-size:15px;color:var(--text-secondary);line-height:1.8;margin-bottom:18px}
.l-body ul,.l-body ol{margin:0 0 22px 20px;color:var(--text-secondary);font-size:15px;line-height:1.8}
.l-body li{margin-bottom:6px}
.l-body strong{color:var(--text-primary);font-weight:600}
.l-body code{
  font-family:var(--font-mono);font-size:12.5px;background:rgba(229,192,123,.08);
  padding:2px 7px;border-radius:4px;color:var(--accent-js);
}
.l-body a{color:var(--accent);text-decoration:underline;text-decoration-color:rgba(255,255,255,.15);text-underline-offset:2px;transition:text-decoration-color .2s}
.l-body a:hover{text-decoration-color:rgba(255,255,255,.4)}

/* code block */
.l-body pre{
  background:var(--bg-code);border:1px solid var(--border);border-radius:var(--radius-sm);
  padding:20px 24px;overflow-x:auto;margin:0 0 28px;font-family:var(--font-mono);
  font-size:13px;line-height:1.85;
}
.l-body pre code{background:none;padding:0;color:var(--text-primary)}

/* example box */
.l-ex{
  background:var(--bg-card);border:1px solid var(--border);
  border-radius:var(--radius-sm);margin:0 0 28px;overflow:hidden;
  box-shadow:0 2px 12px rgba(0,0,0,.15);
}
.l-ex-top{
  padding:10px 16px;background:var(--bg-code);border-bottom:1px solid var(--border);
  display:flex;align-items:center;justify-content:space-between;
}
.l-ex-dots{display:flex;gap:6px}
.l-ex-dots span{width:10px;height:10px;border-radius:50%}
.l-ex-dots span:nth-child(1){background:#ff5f57}
.l-ex-dots span:nth-child(2){background:#febc2e}
.l-ex-dots span:nth-child(3){background:#28c840}
.l-ex-title{font-size:12px;font-weight:600;color:var(--text-muted);margin-left:12px;flex:1}
.l-ex-btn{
  background:rgba(255,255,255,.9);color:#0d0d0d;border:none;padding:5px 14px;border-radius:5px;
  font-size:11px;font-weight:700;cursor:pointer;font-family:var(--font-sans);transition:all .2s;
}
.l-ex-btn:hover{background:#fff;transform:translateY(-1px);box-shadow:0 2px 10px rgba(255,255,255,.1)}
.l-ex-body pre{margin:0;border:0;border-radius:0;background:transparent}

/* callouts */
.l-note{background:rgba(97,175,239,.05);border-left:3px solid var(--accent-css);border-radius:0 var(--radius-sm) var(--radius-sm) 0;padding:14px 20px;margin:22px 0;font-size:14px;line-height:1.7;color:var(--text-secondary)}
.l-note strong{color:var(--accent-css)}
.l-tip{background:rgba(229,192,123,.05);border-left:3px solid var(--accent-js);border-radius:0 var(--radius-sm) var(--radius-sm) 0;padding:14px 20px;margin:22px 0;font-size:14px;line-height:1.7;color:var(--text-secondary)}
.l-tip strong{color:var(--accent-js)}
.l-warn{background:rgba(224,108,117,.05);border-left:3px solid var(--accent-html);border-radius:0 var(--radius-sm) var(--radius-sm) 0;padding:14px 20px;margin:22px 0;font-size:14px;line-height:1.7;color:var(--text-secondary)}
.l-warn strong{color:var(--accent-html)}

/* table */
.l-body table{width:100%;border-collapse:collapse;margin:0 0 22px;font-size:14px;border-radius:var(--radius-sm);overflow:hidden;border:1px solid var(--border)}
.l-body th,.l-body td{padding:11px 16px;border-bottom:1px solid var(--border);text-align:left}
.l-body tr:last-child td{border-bottom:none}
.l-body th{background:rgba(255,255,255,.03);font-weight:600;font-size:12px;text-transform:uppercase;letter-spacing:.5px;color:var(--text-muted)}
.l-body td{color:var(--text-secondary)}

/* nav buttons */
.l-navs{display:flex;gap:12px;margin-top:52px;padding-top:28px;border-top:1px solid var(--border)}
.l-nav-btn{
  flex:1;padding:18px 22px;background:rgba(255,255,255,.02);border:1px solid var(--border);
  border-radius:var(--radius-sm);cursor:pointer;transition:all .25s;max-width:48%;
}
.l-nav-btn:hover{border-color:var(--border-strong);transform:translateY(-2px);background:rgba(255,255,255,.04)}
.l-nav-btn .lbl{font-size:11px;color:var(--text-muted);text-transform:uppercase;letter-spacing:.8px;font-weight:600;margin-bottom:6px}
.l-nav-btn .ttl{font-size:14px;font-weight:600;color:var(--text-primary)}
.l-nav-btn.nxt{text-align:right;margin-left:auto}

/* ═══ FOOTER (index page) ═══ */
.l-footer{
  text-align:center;padding:40px 24px;border-top:1px solid var(--border);margin-top:40px;
  font-size:13px;color:var(--text-muted);
}
.l-footer a{color:var(--text-secondary);transition:color .2s}
.l-footer a:hover{color:var(--text-primary)}

/* ═══ SEO CONTENT ═══ */
.l-seo-content{max-width:900px;margin:0 auto;padding:0 24px 60px}
.l-seo-content h2{color:var(--text-primary);font-size:1.5rem;margin:40px 0 16px;letter-spacing:-0.02em}
.l-seo-content>p{color:var(--text-secondary);line-height:1.7;margin-bottom:24px;font-size:15px}
.l-seo-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:16px;margin:16px 0 32px}
.l-seo-item{background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-sm);padding:20px}
.l-seo-item h3{color:var(--text-primary);font-size:1rem;margin-bottom:8px}
.l-seo-item p{color:var(--text-secondary);font-size:13px;line-height:1.6;margin-bottom:12px}
.l-seo-item a{color:var(--accent);font-size:13px;font-weight:600;text-decoration:none}
.l-seo-item a:hover{color:var(--accent-hover)}
.l-faq{display:flex;flex-direction:column;gap:8px;margin:16px 0}
.l-faq details{background:var(--bg-card);border:1px solid var(--border);border-radius:var(--radius-xs);overflow:hidden}
.l-faq summary{padding:14px 16px;cursor:pointer;color:var(--text-primary);font-weight:500;font-size:14px;list-style:none}
.l-faq summary::-webkit-details-marker{display:none}
.l-faq summary::before{content:'+ ';color:var(--accent);font-weight:700}
.l-faq details[open] summary::before{content:'- '}
.l-faq details p{padding:0 16px 14px;color:var(--text-secondary);font-size:13px;line-height:1.7}

/* ═══ MOBILE ═══ */
@media(max-width:900px){
  .l-nav{padding:0 16px}
  .l-nav .links{display:none}
  .l-sidebar{display:none}
  .l-main{margin-left:0}
  .l-main-inner{padding:24px 20px 60px}
  .l-hero{padding:100px 16px 32px}
  .l-hero h1{font-size:28px;letter-spacing:-1px}
  .l-hero::before{width:300px;height:300px}
  .l-courses{grid-template-columns:1fr;gap:10px}
  .l-card{padding:22px 20px}
  .l-navs{flex-direction:column;gap:10px}
  .l-nav-btn{max-width:100%}
}