:root {
  --bg: #0f172a;
  --text: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --primary: #2563eb;
  --primary-light: #3b82f6;
  --accent: #10b981;
  --accent-light: #34d399;
  --surface: #1e293b;
  --surface-elevated: #334155;
  --surface-hover: #475569;
  --border: #334155;
  --border-hover: #475569;
  --radius: 20px;
  --radius-sm: 12px;
  --shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.3), 0 10px 10px -5px rgba(0, 0, 0, 0.1);
  --shadow-hover: 0 25px 50px -12px rgba(0, 0, 0, 0.4);
  --shadow-accent: 0 10px 30px rgba(16, 185, 129, 0.2);
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", "SF Pro Text", Inter, sans-serif;
  --space-2: 6px;
  --space-3: 9px;
  --space-4: 12px;
  --space-5: 15px;
  --space-6: 18px;
  --space-8: 24px;
  --space-10: 30px;
  --space-12: 36px;
  --space-16: 48px;
  --space-20: 60px;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #ffffff;
    --text: #1e293b;
    --text-secondary: #475569;
    --text-muted: #64748b;
    --surface: #f8fafc;
    --surface-elevated: #f1f5f9;
    --surface-hover: #e2e8f0;
    --border: #e2e8f0;
    --border-hover: #cbd5e1;
    --shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.05), 0 10px 10px -5px rgba(0, 0, 0, 0.03);
    --shadow-hover: 0 25px 50px -12px rgba(0, 0, 0, 0.08);
  }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font);
  background: 
    radial-gradient(ellipse 1200px 800px at 20% -10%, rgba(37, 99, 235, 0.08), transparent 60%),
    radial-gradient(ellipse 1000px 600px at 80% 110%, rgba(16, 185, 129, 0.06), transparent 60%),
    var(--bg);
  color: var(--text);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  min-height: 100vh;
  overflow-x: hidden;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  padding: var(--space-4) var(--space-6);
}

@media (prefers-color-scheme: light) {
  .site-header {
    background: rgba(255, 255, 255, 0.85);
  }
}

.header-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-6);
}

.logo {
  font-weight: 700;
  font-size: 18px;
  color: var(--text);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.logo:hover { color: var(--primary-light); }

.logo-icon {
  width: 32px;
  height: 32px;
}

nav {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

nav a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 14px;
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-sm);
  transition: all 0.2s;
}

nav a:hover {
  color: var(--text);
  background: var(--surface-elevated);
}

nav a.active {
  color: var(--primary-light);
  background: rgba(37, 99, 235, 0.1);
}

.header-cta {
  display: none;
}

@media (min-width: 900px) {
  .header-cta {
    display: inline-flex;
  }
}

.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  color: var(--text);
  padding: var(--space-2);
  cursor: pointer;
}

@media (max-width: 768px) {
  nav { display: none; }
  .mobile-menu-btn { display: block; }
  nav.open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: var(--space-4);
  }
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-4) var(--space-6);
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 14px;
  text-decoration: none;
  transition: all 0.2s;
  border: none;
  cursor: pointer;
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
  color: white;
  box-shadow: 0 4px 14px rgba(37, 99, 235, 0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(37, 99, 235, 0.4);
}

.btn-large {
  padding: var(--space-5) var(--space-8);
  font-size: 16px;
  letter-spacing: 0.02em;
}

.btn-secondary {
  background: var(--surface-elevated);
  color: var(--text);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: var(--surface-hover);
  border-color: var(--border-hover);
}

.btn-accent {
  background: linear-gradient(135deg, var(--accent) 0%, var(--accent-light) 100%);
  color: white;
  box-shadow: 0 4px 14px rgba(16, 185, 129, 0.3);
}

.btn-accent:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(16, 185, 129, 0.4);
}

/* Container */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 clamp(var(--space-4), 5vw, var(--space-8));
}

.container-narrow {
  max-width: 800px;
}

/* Hero */
.hero {
  padding: clamp(var(--space-16), 10vh, var(--space-20)) 0;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  pointer-events: none;
  z-index: -1;
}

.hero h1 {
  margin: 0 0 var(--space-6);
  font-weight: 800;
  font-size: clamp(32px, 7vw, 56px);
  line-height: 1.1;
  letter-spacing: -0.02em;
  background: linear-gradient(135deg, var(--text) 0%, var(--primary-light) 60%, var(--accent) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: clamp(16px, 3vw, 20px);
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto var(--space-8);
  line-height: 1.6;
}

.hero-features {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-4);
  margin-bottom: var(--space-10);
}

.hero-feature {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  color: var(--text-muted);
  font-size: 14px;
}

.hero-feature svg {
  color: var(--accent);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-4);
}

/* Sections */
section {
  padding: clamp(var(--space-12), 8vh, var(--space-20)) 0;
}

section h2 {
  font-size: clamp(24px, 5vw, 36px);
  font-weight: 700;
  margin: 0 0 var(--space-4);
  line-height: 1.2;
}

section .section-subtitle {
  color: var(--text-secondary);
  font-size: 18px;
  margin: 0 0 var(--space-12);
  max-width: 600px;
}

.text-center { text-align: center; }
.text-center .section-subtitle { margin-left: auto; margin-right: auto; }

/* Cards */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 320px), 1fr));
  gap: var(--space-6);
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-8);
  transition: all 0.2s;
  position: relative;
  overflow: hidden;
}

.card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--primary), transparent);
  opacity: 0;
  transition: opacity 0.2s;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-hover);
  border-color: var(--border-hover);
}

.card:hover::before {
  opacity: 1;
}

.card-featured {
  border-color: var(--accent);
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.08) 0%, rgba(37, 99, 235, 0.05) 100%), var(--surface);
}

.card-featured::before {
  background: linear-gradient(90deg, transparent, var(--accent), transparent);
  opacity: 1;
}

.card h3 {
  font-size: 20px;
  font-weight: 600;
  margin: 0 0 var(--space-4);
}

.card p {
  color: var(--text-secondary);
  margin: 0 0 var(--space-6);
  line-height: 1.6;
}

.card-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--space-6);
}

.card-icon svg {
  width: 24px;
  height: 24px;
  color: white;
}

/* Badges */
.badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  background: rgba(16, 185, 129, 0.15);
  color: var(--accent);
  border-radius: 100px;
  font-size: 12px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  border: 1px solid rgba(16, 185, 129, 0.3);
}

.badge-blue {
  background: rgba(37, 99, 235, 0.15);
  color: var(--primary-light);
  border-color: rgba(37, 99, 235, 0.3);
}

/* Feature list */
.feature-list {
  list-style: none;
  padding: 0;
  margin: 0 0 var(--space-6);
}

.feature-list li {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  margin-bottom: var(--space-4);
  color: var(--text-secondary);
}

.feature-list svg {
  flex-shrink: 0;
  color: var(--accent);
  margin-top: 2px;
}

/* Callout */
.callout {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-8);
  text-align: center;
}

.callout-highlight {
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.1) 0%, rgba(37, 99, 235, 0.08) 100%);
  border-color: var(--accent);
}

.callout h3 {
  font-size: 24px;
  margin: 0 0 var(--space-4);
}

.callout p {
  color: var(--text-secondary);
  margin: 0 0 var(--space-6);
  max-width: 500px;
  margin-left: auto;
  margin-right: auto;
}

/* Article layout */
.article-header {
  text-align: center;
  padding: clamp(var(--space-12), 8vh, var(--space-16)) 0;
  border-bottom: 1px solid var(--border);
  margin-bottom: var(--space-12);
}

.article-header h1 {
  font-size: clamp(28px, 6vw, 44px);
  margin: 0 0 var(--space-4);
  background: linear-gradient(135deg, var(--text) 0%, var(--primary-light) 60%, var(--accent) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.article-header .subtitle {
  font-size: 18px;
  color: var(--text-secondary);
  margin: 0 0 var(--space-6);
}

.article-content {
  max-width: 720px;
  margin: 0 auto;
  padding-bottom: var(--space-16);
}

.article-content h2 {
  font-size: 24px;
  margin: var(--space-12) 0 var(--space-6);
}

.article-content h3 {
  font-size: 20px;
  margin: var(--space-8) 0 var(--space-4);
}

.article-content p {
  color: var(--text-secondary);
  margin: 0 0 var(--space-6);
  line-height: 1.8;
}

.article-content ul, .article-content ol {
  color: var(--text-secondary);
  margin: 0 0 var(--space-6);
  padding-left: var(--space-6);
  line-height: 1.8;
}

.article-content li {
  margin-bottom: var(--space-3);
}

.toc {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-6);
  margin-bottom: var(--space-12);
}

.toc h4 {
  font-size: 14px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
  margin: 0 0 var(--space-4);
}

.toc ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.toc li {
  margin-bottom: var(--space-2);
}

.toc a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 14px;
  transition: color 0.2s;
}

.toc a:hover {
  color: var(--primary-light);
}

/* Footer */
.site-footer {
  margin-top: auto;
  padding: var(--space-12) 0 var(--space-8);
  border-top: 1px solid var(--border);
  background: var(--surface);
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: var(--space-8);
  margin-bottom: var(--space-8);
}

.footer-section h4 {
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
  margin: 0 0 var(--space-4);
}

.footer-section ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.footer-section li {
  margin-bottom: var(--space-2);
}

.footer-section a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 14px;
  transition: color 0.2s;
}

.footer-section a:hover {
  color: var(--primary-light);
}

.footer-bottom {
  padding-top: var(--space-6);
  border-top: 1px solid var(--border);
  text-align: center;
  font-size: 13px;
  color: var(--text-muted);
}

.footer-bottom a {
  color: var(--text-muted);
  text-decoration: none;
}

.footer-bottom a:hover {
  color: var(--primary-light);
}

/* Animations */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}

@keyframes pulse {
  0%, 100% { opacity: 0.4; }
  50% { opacity: 0.8; }
}

.animate-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.animate-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Hero animation elements */
.hero-node {
  position: absolute;
  border-radius: 50%;
  background: var(--primary);
  opacity: 0.2;
  animation: float 6s ease-in-out infinite;
}

.hero-line {
  position: absolute;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--primary), transparent);
  opacity: 0.15;
  animation: pulse 4s ease-in-out infinite;
}

/* Utility */
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

/* Link styling */
a { color: var(--primary-light); text-decoration: none; transition: color 0.2s; }
a:hover { color: var(--accent); }

/* Highlight box */
.highlight-box {
  background: rgba(16, 185, 129, 0.1);
  border-left: 4px solid var(--accent);
  padding: var(--space-6);
  margin: var(--space-8) 0;
  border-radius: 0 8px 8px 0;
}

.highlight-box p { margin: 0; color: var(--text-secondary); }