:root{
  --bg:#09101f;
  --bg-2:#101933;
  --panel:#131d3b;
  --panel-2:#1b2750;
  --text:#edf3ff;
  --muted:#b5c2e3;
  --primary:#57b5ff;
  --primary-2:#2e8fe0;
  --accent:#7af3d1;
  --border:rgba(255,255,255,.08);
  --shadow:0 18px 40px rgba(0,0,0,.30);
  --radius:20px;
  --max:1180px;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  font-family:Arial,Helvetica,sans-serif;
  color:var(--text);
  background:
    radial-gradient(circle at top left, rgba(87,181,255,.16), transparent 26%),
    radial-gradient(circle at top right, rgba(122,243,209,.12), transparent 22%),
    linear-gradient(180deg, #09101f 0%, #0b1430 100%);
  line-height:1.7;
}
img{max-width:100%;display:block}
a{text-decoration:none;color:inherit}
code, pre{font-family:Consolas, Monaco, "Courier New", monospace}
.container{width:min(92%,var(--max));margin:0 auto}
.section{padding:84px 0}
.eyebrow{
  display:inline-flex;align-items:center;gap:10px;
  padding:8px 14px;border:1px solid var(--border);
  border-radius:999px;background:rgba(255,255,255,.05);
  color:#d6e6ff;font-size:.9rem;font-weight:700;
  margin-bottom:18px;
}
.eyebrow::before{
  content:"";width:8px;height:8px;border-radius:50%;
  background:var(--accent);box-shadow:0 0 14px rgba(122,243,209,.6);
}
.section-title{font-size:clamp(1.9rem, 3vw, 2.7rem);line-height:1.15;margin-bottom:14px}
.section-subtitle{color:var(--muted);max-width:840px;margin-bottom:34px;font-size:1.03rem}
header{
  position:sticky;top:0;z-index:1000;
  background:rgba(9,16,31,.82);
  backdrop-filter:blur(12px);
  border-bottom:1px solid var(--border);
}
.navbar{
  min-height:76px;
  display:flex;align-items:center;justify-content:space-between;gap:18px;
}
.brand{
  display:flex;align-items:center;gap:12px;
  font-weight:800;font-size:1.35rem;letter-spacing:.2px;
}
.brand-mark{
  width:40px;height:40px;border-radius:12px;
  background:linear-gradient(135deg,var(--primary),var(--primary-2));
  display:flex;align-items:center;justify-content:center;
  box-shadow:var(--shadow);
  color:#fff;font-weight:800;font-size:1rem;
}
.brand span{color:var(--primary)}
nav ul{list-style:none;display:flex;gap:24px;flex-wrap:wrap}
nav a{color:var(--muted);font-weight:700}
nav a:hover{color:#fff}
.header-actions{display:flex;gap:12px;align-items:center}
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:10px;
  padding:14px 22px;border-radius:999px;font-weight:800;
  transition:transform .2s ease, opacity .2s ease, border-color .2s ease;
  border:1px solid transparent;
}
.btn:hover{transform:translateY(-2px);opacity:.98}
.btn-primary{background:linear-gradient(135deg,var(--primary),var(--primary-2));color:#fff;box-shadow:var(--shadow)}
.btn-secondary{background:rgba(255,255,255,.05);color:#fff;border-color:var(--border)}
.hero{padding:88px 0 64px}
.hero-grid{display:grid;grid-template-columns:1.08fr .92fr;gap:34px;align-items:center}
.hero h1{font-size:clamp(2.4rem,5vw,4.3rem);line-height:1.05;margin-bottom:20px}
.hero h1 .highlight{color:var(--primary)}
.hero p{max-width:760px;color:var(--muted);font-size:1.08rem;margin-bottom:28px}
.hero-actions{display:flex;gap:14px;flex-wrap:wrap;margin-bottom:28px}
.trust-row{display:flex;gap:10px;flex-wrap:wrap}
.trust-row span{
  padding:10px 14px;border-radius:999px;background:rgba(255,255,255,.05);
  border:1px solid var(--border);color:var(--muted);font-size:.95rem;font-weight:700;
}
.hero-panel, .card, .lesson-shell, .info-box{
  background:linear-gradient(180deg, rgba(255,255,255,.06), rgba(255,255,255,.03));
  border:1px solid var(--border);
  border-radius:24px;
  box-shadow:var(--shadow);
}
.hero-panel{padding:28px}
.panel-top{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-bottom:20px}
.pill{
  display:inline-flex;align-items:center;gap:8px;padding:8px 12px;border-radius:999px;
  background:rgba(87,181,255,.14);color:#d9edff;font-size:.86rem;font-weight:800;
}
.grid-3, .grid-4, .lesson-grid, .stats-grid{display:grid;gap:22px}
.grid-3{grid-template-columns:repeat(3,1fr)}
.grid-4{grid-template-columns:repeat(4,1fr)}
.lesson-grid{grid-template-columns:repeat(3,1fr)}
.stats-grid{grid-template-columns:repeat(4,1fr)}
.card{padding:24px}
.card:hover{transform:translateY(-4px);border-color:rgba(87,181,255,.34)}
.icon{
  width:54px;height:54px;border-radius:16px;display:flex;align-items:center;justify-content:center;
  background:rgba(87,181,255,.14);color:var(--primary);font-weight:800;font-size:1.05rem;margin-bottom:16px;
}
.card h3{font-size:1.15rem;line-height:1.25;margin-bottom:10px}
.card p{color:var(--muted);margin-bottom:14px}
.card .link{color:var(--accent);font-weight:800}
.stat{
  text-align:center;background:rgba(255,255,255,.04);border:1px solid var(--border);
  border-radius:18px;padding:18px;box-shadow:var(--shadow);
}
.stat strong{display:block;color:var(--accent);font-size:1.6rem;margin-bottom:6px}
.stat span{color:var(--muted);font-size:.96rem}
.lesson-card{display:flex;flex-direction:column;height:100%}
.lesson-number{
  display:inline-flex;align-items:center;justify-content:center;width:44px;height:44px;border-radius:50%;
  background:linear-gradient(135deg,var(--primary),var(--primary-2));color:#fff;font-weight:800;margin-bottom:16px;
}
.lesson-card h3{font-size:1.1rem;margin-bottom:10px}
.lesson-card p{color:var(--muted);margin-bottom:14px;flex:1}
.lesson-tags{display:flex;gap:10px;flex-wrap:wrap;margin-bottom:16px}
.lesson-tags span{
  font-size:.82rem;font-weight:700;padding:7px 10px;border-radius:999px;border:1px solid var(--border);
  background:rgba(255,255,255,.04);color:#dbe8ff;
}
.split{display:grid;grid-template-columns:1fr 1fr;gap:24px;align-items:start}
.list-panel{
  background:linear-gradient(180deg,var(--panel),var(--panel-2));
  border:1px solid var(--border);border-radius:24px;padding:28px;box-shadow:var(--shadow);
}
.check-list{list-style:none;display:grid;gap:12px}
.check-list li{
  background:rgba(255,255,255,.04);border:1px solid var(--border);border-radius:14px;
  padding:13px 14px;color:var(--text);
}
.check-list li strong{color:#fff}
footer{border-top:1px solid var(--border);background:rgba(0,0,0,.18);padding:34px 0}
.footer-grid{display:grid;grid-template-columns:1.2fr .8fr;gap:26px}
.footer-links{display:flex;flex-wrap:wrap;gap:14px 18px;justify-content:flex-end}
.footer-links a{color:var(--muted)}
.footer-links a:hover{color:#fff}
.footer-brand p{max-width:620px;color:var(--muted);margin-top:10px}
.copyright{margin-top:18px;color:#94a2cb;font-size:.92rem}

/* lesson pages */
.lesson-hero{padding:72px 0 40px}
.breadcrumbs{color:var(--muted);font-size:.95rem;margin-bottom:16px}
.breadcrumbs a{color:var(--muted)}
.breadcrumbs a:hover{color:#fff}
.lesson-shell{padding:30px}
.lesson-shell h1{font-size:clamp(2rem, 4vw, 3.2rem);line-height:1.08;margin-bottom:14px}
.lesson-meta{display:flex;gap:12px;flex-wrap:wrap;margin-bottom:20px}
.meta-pill{
  display:inline-flex;align-items:center;gap:8px;padding:8px 12px;border-radius:999px;
  background:rgba(255,255,255,.05);border:1px solid var(--border);color:#dbe8ff;font-weight:700;font-size:.88rem;
}
.lesson-intro{color:var(--muted);font-size:1.05rem;max-width:900px}
.content-grid{display:grid;grid-template-columns:.88fr 1.12fr;gap:24px;margin-top:24px}
.sidebar-stack{display:grid;gap:22px}
.info-box{padding:22px}
.info-box h3{margin-bottom:12px;font-size:1.05rem}
.info-box p{color:var(--muted)}
.info-box ul{padding-left:18px}
.info-box li{margin:8px 0;color:var(--text)}
.lesson-content{display:grid;gap:22px}
.section-card{
  background:linear-gradient(180deg,var(--panel),var(--panel-2));
  border:1px solid var(--border);border-radius:22px;padding:24px;box-shadow:var(--shadow);
}
.section-card h2{font-size:1.35rem;margin-bottom:12px}
.section-card h3{font-size:1.08rem;margin:16px 0 10px}
.section-card p{color:var(--muted);margin:12px 0}
.examples{display:grid;gap:14px}
.example{
  background:rgba(255,255,255,.04);border:1px solid var(--border);border-radius:16px;padding:16px;
}
.example strong{display:block;margin-bottom:6px}
.code-block{
  background:#08101f;border:1px solid rgba(255,255,255,.08);border-radius:18px;padding:18px;overflow:auto;
}
.code-block pre{white-space:pre;line-height:1.6;color:#dff5ff}
.note-list{padding-left:18px}
.note-list li{margin:8px 0}
.nav-row{
  display:flex;justify-content:space-between;gap:16px;flex-wrap:wrap;margin-top:10px;
}
.nav-link{
  flex:1;min-width:220px;
  background:rgba(255,255,255,.04);border:1px solid var(--border);border-radius:18px;padding:16px;
}
.nav-label{display:block;color:var(--muted);font-size:.85rem;margin-bottom:6px}
.nav-title{font-weight:800}
@media (max-width:1024px){
  .hero-grid,.grid-4,.grid-3,.stats-grid,.lesson-grid,.split,.footer-grid,.content-grid{grid-template-columns:1fr}
  nav{display:none}
  .footer-links{justify-content:flex-start}
}
@media (max-width:640px){
  .hero{padding-top:72px}
  .section,.lesson-hero{padding-top:64px;padding-bottom:64px}
  .hero-panel,.card,.list-panel,.lesson-shell,.section-card,.info-box{padding:22px}
  .hero-actions,.header-actions{flex-direction:column;align-items:stretch}
  .btn{width:100%}
  .brand{font-size:1.18rem}
}