:root{
  --bg:#0d0f12;
  --bg2:#15191f;
  --panel:#161b22;
  --line:#232a33;
  --text:#e9eef3;
  --muted:#9aa6b2;
  --cyan:#28aaff;
  --cyan2:#0b6fff;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  background:radial-gradient(1200px 600px at 50% -10%,#1a2230 0%,var(--bg) 60%);
  color:var(--text);
  line-height:1.75;
  -webkit-font-smoothing:antialiased;
}
a{color:var(--cyan);text-decoration:none}
a:hover{text-decoration:underline}

/* Nav */
.nav{
  position:sticky;top:0;z-index:10;
  display:flex;align-items:center;justify-content:space-between;
  padding:14px 28px;
  background:rgba(13,15,18,.82);
  backdrop-filter:blur(10px);
  border-bottom:1px solid var(--line);
}
.nav .logo{height:34px;width:auto;display:block}
.nav-links{display:flex;gap:24px;font-size:14px;font-weight:600}
.nav-links a{color:var(--muted)}
.nav-links a:hover{color:var(--text);text-decoration:none}

/* Hero */
.hero{
  max-width:880px;margin:0 auto;padding:64px 24px 20px;text-align:center;
}
.hero h1{font-size:clamp(30px,5vw,46px);font-weight:800;letter-spacing:-.5px}
.hero .accent{height:3px;width:90px;margin:18px auto;background:linear-gradient(90deg,var(--cyan2),var(--cyan))}
.hero p{color:var(--muted);font-size:15px}
.hero .lede{max-width:680px;margin:14px auto 0;color:#c3cdd8;font-size:16px}

/* Layout with TOC */
.wrap{max-width:1080px;margin:0 auto;padding:24px 24px 80px;display:grid;grid-template-columns:240px 1fr;gap:28px}
.toc{
  position:sticky;top:80px;align-self:start;
  background:linear-gradient(180deg,rgba(22,27,34,.7),rgba(18,22,28,.7));
  border:1px solid var(--line);border-radius:14px;padding:20px;
}
.toc h4{font-size:12px;letter-spacing:1.5px;color:var(--cyan);margin-bottom:12px;text-transform:uppercase}
.toc a{display:block;color:var(--muted);font-size:13px;padding:5px 0;line-height:1.4}
.toc a:hover{color:var(--text);text-decoration:none}

/* Content card */
.card{
  background:linear-gradient(180deg,rgba(22,27,34,.9),rgba(18,22,28,.9));
  border:1px solid var(--line);
  border-radius:16px;
  padding:44px 48px;
  min-width:0;
}
.card h2{font-size:21px;margin:36px 0 12px;color:#fff;font-weight:700;scroll-margin-top:90px}
.card h2:first-of-type{margin-top:0}
.card h3{font-size:16px;margin:22px 0 8px;color:#dbe4ee}
.card p,.card li{color:#c3cdd8;font-size:15px;margin-bottom:13px}
.card ul,.card ol{margin:0 0 16px 24px}
.card li{margin-bottom:9px}
.card strong{color:#fff}
.tag{
  display:inline-block;font-size:12px;letter-spacing:1px;color:var(--cyan);
  border:1px solid var(--line);border-radius:20px;padding:5px 14px;margin-bottom:8px;
}
.note{
  background:rgba(40,170,255,.06);
  border:1px solid rgba(40,170,255,.25);
  border-left:3px solid var(--cyan);
  border-radius:10px;padding:16px 18px;margin:18px 0;
}
.note p{margin-bottom:0;color:#cfe3f5}
.divider{height:1px;background:var(--line);margin:30px 0}

/* Footer */
.footer{
  border-top:1px solid var(--line);
  text-align:center;padding:34px 24px;color:var(--muted);font-size:13px;
}
.footer .logo{height:30px;width:auto;margin-bottom:14px;opacity:.95}
.footer a{color:var(--muted)}
.footer .links{margin-top:6px}

@media(max-width:860px){
  .wrap{grid-template-columns:1fr;gap:18px}
  .toc{position:static;order:2}
}
@media(max-width:600px){
  .nav{padding:12px 18px}
  .nav .logo{height:28px}
  .nav-links{gap:16px;font-size:13px}
  .card{padding:26px 22px}
}