/* === LearnHub Design System — Modern Dark === */
:root {
  --bg: #0a0a0f;
  --bg-alt: #111118;
  --surface: #16161e;
  --surface-hover: #1c1c26;
  --surface-raised: #1e1e2a;
  --border: #252530;
  --border-light: #2a2a38;
  --text: #ececf1;
  --text-secondary: #b4b4c0;
  --text-muted: #6e6e7e;
  --accent: #818cf8;
  --accent-soft: #6366f1;
  --accent-glow: rgba(99, 102, 241, 0.15);
  --green: #34d399;
  --green-bg: rgba(52, 211, 153, 0.1);
  --amber: #fbbf24;
  --amber-bg: rgba(251, 191, 36, 0.1);
  --red: #f87171;
  --red-bg: rgba(248, 113, 113, 0.1);
  --pink: #f472b6;
  --cyan: #22d3ee;
  --radius: 14px;
  --radius-sm: 8px;
  --radius-lg: 20px;
  --shadow: 0 1px 2px rgba(0,0,0,0.3);
  --shadow-lg: 0 8px 32px rgba(0,0,0,0.4);
  --shadow-glow: 0 0 40px var(--accent-glow);
  --font: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", monospace;
  --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a { color: var(--accent); text-decoration: none; transition: color var(--transition); }
a:hover { color: var(--text); }

::selection { background: var(--accent); color: var(--bg); }

.container { max-width: 960px; margin: 0 auto; padding: 0 32px; }

/* === Header === */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  background: rgba(10, 10, 15, 0.75);
  border-bottom: 1px solid var(--border);
  padding: 14px 0;
}
.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.logo {
  font-size: 19px;
  font-weight: 700;
  letter-spacing: -0.5px;
  color: var(--text);
  display: flex;
  align-items: center;
  gap: 6px;
}
.logo::before {
  content: "";
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 12px var(--accent);
}
.logo span { color: var(--accent); }
.nav-links { display: flex; gap: 20px; align-items: center; flex-wrap: wrap; }
.nav-links a {
  font-size: 13px;
  font-weight: 500;
  color: var(--text-muted);
  transition: color var(--transition);
  padding: 4px 0;
}
.nav-links a:hover { color: var(--text); }

/* === Hero === */
.hero {
  padding: 100px 0 80px;
  text-align: center;
  position: relative;
  overflow: hidden;
}
.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 800px 400px at 50% 0%, rgba(99, 102, 241, 0.08), transparent 70%);
  pointer-events: none;
}
.hero h1 {
  font-size: 56px;
  font-weight: 800;
  letter-spacing: -2px;
  margin-bottom: 20px;
  line-height: 1.05;
  background: linear-gradient(135deg, #ececf1 0%, #a5b4fc 50%, #818cf8 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero p {
  font-size: 18px;
  color: var(--text-secondary);
  max-width: 560px;
  margin: 0 auto;
  line-height: 1.6;
}

/* === Cards === */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(256px, 1fr));
  gap: 16px;
  padding: 48px 0 64px;
}
.card {
  display: block;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  transition: border-color var(--transition-slow), box-shadow var(--transition-slow), transform var(--transition-slow);
  position: relative;
  overflow: hidden;
}
.card::before {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(400px circle at var(--mouse-x, 50%) var(--mouse-y, 50%), var(--accent-glow), transparent 60%);
  opacity: 0;
  transition: opacity var(--transition-slow);
}
.card:hover {
  border-color: var(--accent);
  box-shadow: var(--shadow-lg), 0 0 0 1px var(--accent-soft);
  transform: translateY(-3px);
}
.card:hover::before { opacity: 1; }
.card-icon {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 18px;
  margin-bottom: 14px;
  background: var(--accent-glow);
  border: 1px solid rgba(99, 102, 241, 0.2);
  position: relative;
  z-index: 1;
}
.card h3 {
  font-size: 15px;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text);
  position: relative;
  z-index: 1;
}
.card p {
  font-size: 13px;
  color: var(--text-muted);
  line-height: 1.5;
  position: relative;
  z-index: 1;
}

/* === Section === */
.section { padding: 80px 0; }
.section-title {
  font-size: 30px;
  font-weight: 700;
  margin-bottom: 8px;
  letter-spacing: -0.5px;
}
.section-desc {
  color: var(--text-muted);
  margin-bottom: 8px;
  font-size: 15px;
}

/* === Content Pages === */
.content-page {
  padding: 80px 0;
  max-width: 720px;
}
.content-page h1 {
  font-size: 40px;
  font-weight: 800;
  margin-bottom: 8px;
  letter-spacing: -1.5px;
  background: linear-gradient(135deg, var(--text) 0%, var(--accent) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.content-page .meta {
  color: var(--text-secondary);
  font-size: 14px;
  margin-bottom: 40px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border);
}
.content-page h2 {
  font-size: 22px;
  font-weight: 600;
  margin: 40px 0 14px;
  color: var(--text);
  letter-spacing: -0.3px;
}
.content-page p {
  margin-bottom: 16px;
  color: var(--text-secondary);
}
.content-page ul, .content-page ol {
  margin: 16px 0;
  padding-left: 20px;
}
.content-page li {
  margin-bottom: 10px;
  color: var(--text-secondary);
  line-height: 1.6;
}
.content-page li strong {
  color: var(--text);
}
.content-page ol {
  list-style: none;
  counter-reset: step;
}
.content-page ol li {
  counter-increment: step;
  position: relative;
  padding-left: 28px;
}
.content-page ol li::before {
  content: counter(step);
  position: absolute;
  left: 0;
  top: 0;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  background: var(--accent-glow);
  border: 1px solid rgba(99, 102, 241, 0.3);
  color: var(--accent);
  font-size: 11px;
  font-weight: 600;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
}

/* Code Block */
.code-block {
  background: #0d0d14;
  color: #a5b4fc;
  padding: 20px 24px;
  border-radius: var(--radius);
  font-family: var(--font-mono);
  font-size: 13px;
  overflow-x: auto;
  margin: 20px 0;
  line-height: 1.7;
  border: 1px solid var(--border);
  position: relative;
}
.code-block::before {
  content: "// code";
  display: block;
  color: var(--text-muted);
  font-size: 11px;
  font-weight: 500;
  margin-bottom: 10px;
  letter-spacing: 0.5px;
  text-transform: uppercase;
}

/* === Footer === */
.site-footer {
  padding: 48px 0;
  text-align: center;
  color: var(--text-muted);
  font-size: 13px;
  border-top: 1px solid var(--border);
  margin-top: 64px;
}
.site-footer a { color: var(--text-secondary); }
.site-footer a:hover { color: var(--accent); }

/* === Scrollbar === */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-muted); }

/* === Responsive === */
@media (max-width: 768px) {
  .hero h1 { font-size: 36px; }
  .card-grid { grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 12px; }
  .nav-links { gap: 12px; }
  .content-page h1 { font-size: 30px; }
  .content-page { padding: 48px 0; }
}

@media (max-width: 480px) {
  .hero h1 { font-size: 28px; letter-spacing: -1px; }
  .card-grid { grid-template-columns: 1fr 1fr; gap: 10px; }
  .card { padding: 18px; }
  .card h3 { font-size: 13px; }
  .card p { font-size: 11px; }
  .container { padding: 0 20px; }
}