/* ═══════════════════════════════════════════════════════════
   QUANTUM FINANCE — Global Design System
   Theme: Dark quantum-inspired with glassmorphism
   ═══════════════════════════════════════════════════════════ */

/* ── Google Fonts ── */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Outfit:wght@400;500;600;700;800&family=Fira+Code:wght@400;500&display=swap');

/* ── CSS Custom Properties ── */
:root {
  /* Colors */
  --bg-primary: #0a0e27;
  --bg-secondary: #111638;
  --bg-card: rgba(17, 22, 56, 0.6);
  --bg-card-hover: rgba(25, 32, 72, 0.8);
  --bg-surface: rgba(255, 255, 255, 0.03);

  --text-primary: #e8eaf6;
  --text-secondary: #9ea4c1;
  --text-muted: #6b7194;

  --accent-blue: #00d4ff;
  --accent-purple: #7c3aed;
  --accent-pink: #ec4899;
  --accent-green: #10b981;
  --accent-orange: #f59e0b;
  --accent-red: #ef4444;

  --gradient-hero: linear-gradient(135deg, #0a0e27 0%, #1a1045 40%, #0d1a3a 100%);
  --gradient-card: linear-gradient(135deg, rgba(124,58,237,0.08), rgba(0,212,255,0.08));
  --gradient-accent: linear-gradient(135deg, #7c3aed, #00d4ff);
  --gradient-btn: linear-gradient(135deg, #7c3aed, #00d4ff);

  --border-subtle: rgba(124, 58, 237, 0.15);
  --border-glow: rgba(0, 212, 255, 0.3);

  --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.3);
  --shadow-card-hover: 0 8px 40px rgba(124, 58, 237, 0.2);
  --shadow-glow: 0 0 30px rgba(0, 212, 255, 0.15);

  /* Typography */
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-heading: 'Outfit', 'Inter', sans-serif;
  --font-mono: 'Fira Code', 'Consolas', monospace;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;

  /* Radii */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  /* Transitions */
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --transition-fast: 0.2s var(--ease-out);
  --transition-med: 0.35s var(--ease-out);
  --transition-slow: 0.5s var(--ease-out);
}

/* ── Reset & Base ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  scroll-behavior: smooth;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: var(--font-body);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  min-height: 100vh;
  overflow-x: hidden;
}

/* Animated background */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background: var(--gradient-hero);
  z-index: -2;
}
body::after {
  content: '';
  position: fixed;
  inset: 0;
  background:
    radial-gradient(ellipse 600px 400px at 20% 30%, rgba(124,58,237,0.08), transparent),
    radial-gradient(ellipse 500px 350px at 80% 70%, rgba(0,212,255,0.06), transparent);
  z-index: -1;
  animation: bgPulse 12s ease-in-out infinite alternate;
}

@keyframes bgPulse {
  0%   { opacity: 0.6; }
  100% { opacity: 1; }
}

/* ── Typography ── */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.25;
  color: var(--text-primary);
}
h1 { font-size: clamp(2rem, 5vw, 3.2rem); }
h2 { font-size: clamp(1.5rem, 3.5vw, 2.2rem); }
h3 { font-size: clamp(1.2rem, 2.5vw, 1.6rem); }
h4 { font-size: 1.15rem; }

p { color: var(--text-secondary); margin-bottom: var(--space-md); }

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

/* ══════════════════════════════════════════
   HEADER
   ══════════════════════════════════════════ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(10, 14, 39, 0.8);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border-subtle);
  padding: 0 var(--space-xl);
}
.header-inner {
  max-width: 1280px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}
.header-logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--text-primary);
  text-decoration: none;
}
.header-logo .logo-icon {
  width: 32px;
  height: 32px;
  background: var(--gradient-accent);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
}
.header-nav { display: flex; gap: var(--space-lg); align-items: center; }
.header-nav a {
  color: var(--text-secondary);
  font-size: 0.875rem;
  font-weight: 500;
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}
.header-nav a:hover,
.header-nav a.active {
  color: var(--accent-blue);
  background: rgba(0, 212, 255, 0.08);
}
.back-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--text-secondary);
  font-size: 0.875rem;
  font-weight: 500;
  transition: color var(--transition-fast);
}
.back-link:hover { color: var(--accent-blue); }

/* Mobile hamburger */
.nav-toggle { display: none; background: none; border: none; color: var(--text-primary); font-size: 1.5rem; cursor: pointer; }

@media (max-width: 768px) {
  .nav-toggle { display: block; }
  .header-nav {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: rgba(10, 14, 39, 0.95);
    backdrop-filter: blur(20px);
    flex-direction: column;
    padding: var(--space-lg);
    border-bottom: 1px solid var(--border-subtle);
  }
  .header-nav.open { display: flex; }
}

/* ══════════════════════════════════════════
   FOOTER
   ══════════════════════════════════════════ */
.site-footer {
  background: rgba(10, 14, 39, 0.9);
  border-top: 1px solid var(--border-subtle);
  padding: var(--space-2xl) var(--space-xl);
  margin-top: var(--space-3xl);
}
.footer-inner {
  max-width: 1280px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: var(--space-xl);
}
.footer-col h4 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: var(--accent-blue);
  margin-bottom: var(--space-md);
}
.footer-col p, .footer-col a {
  font-size: 0.875rem;
  color: var(--text-muted);
  line-height: 1.8;
}
.footer-bottom {
  max-width: 1280px;
  margin: var(--space-xl) auto 0;
  padding-top: var(--space-lg);
  border-top: 1px solid var(--border-subtle);
  text-align: center;
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ══════════════════════════════════════════
   HERO SECTION
   ══════════════════════════════════════════ */
.hero {
  text-align: center;
  padding: var(--space-3xl) var(--space-xl);
  position: relative;
}
.hero-badge {
  display: inline-block;
  padding: 6px 18px;
  border-radius: 50px;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 1px;
  text-transform: uppercase;
  background: rgba(124, 58, 237, 0.15);
  color: var(--accent-purple);
  border: 1px solid rgba(124, 58, 237, 0.3);
  margin-bottom: var(--space-lg);
}
.hero h1 {
  margin-bottom: var(--space-md);
}
.hero h1 .gradient-text {
  background: var(--gradient-accent);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero-subtitle {
  font-size: 1.15rem;
  color: var(--text-secondary);
  max-width: 640px;
  margin: 0 auto var(--space-lg);
}
.hero-meta {
  display: flex;
  justify-content: center;
  gap: var(--space-xl);
  flex-wrap: wrap;
  margin-top: var(--space-lg);
}
.hero-meta-item {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.9rem;
  color: var(--text-muted);
}
.hero-meta-item .icon { font-size: 1.2rem; }

/* ══════════════════════════════════════════
   CARD GRID
   ══════════════════════════════════════════ */
.section-title {
  text-align: center;
  margin-bottom: var(--space-2xl);
}
.section-title h2 { margin-bottom: var(--space-sm); }
.section-title p { color: var(--text-muted); }

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: var(--space-xl);
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 var(--space-xl);
}

.card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  position: relative;
  overflow: hidden;
  cursor: pointer;
  transition: all var(--transition-med);
  text-decoration: none;
  display: flex;
  flex-direction: column;
}
.card::before {
  content: '';
  position: absolute;
  inset: 0;
  background: var(--gradient-card);
  opacity: 0;
  transition: opacity var(--transition-med);
}
.card:hover {
  transform: translateY(-6px);
  border-color: var(--border-glow);
  box-shadow: var(--shadow-card-hover), var(--shadow-glow);
}
.card:hover::before { opacity: 1; }

.card-header {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
  position: relative;
  z-index: 1;
}
.card-number {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  background: var(--gradient-accent);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: 1.1rem;
  color: #fff;
  flex-shrink: 0;
}
.card-duration {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--accent-blue);
  background: rgba(0, 212, 255, 0.1);
  padding: 3px 10px;
  border-radius: 50px;
  margin-left: auto;
}
.card-title {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: var(--space-sm);
  position: relative;
  z-index: 1;
  color: var(--text-primary);
}
.card-desc {
  font-size: 0.875rem;
  color: var(--text-muted);
  line-height: 1.65;
  position: relative;
  z-index: 1;
  flex: 1;
}
.card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: var(--space-lg);
  position: relative;
  z-index: 1;
}
.card-tags {
  display: flex;
  gap: var(--space-xs);
  flex-wrap: wrap;
}
.card-tag {
  font-size: 0.7rem;
  padding: 2px 8px;
  border-radius: 50px;
  background: rgba(255,255,255,0.05);
  color: var(--text-muted);
  border: 1px solid rgba(255,255,255,0.06);
}
.card-arrow {
  font-size: 1.2rem;
  color: var(--accent-blue);
  transition: transform var(--transition-fast);
}
.card:hover .card-arrow { transform: translateX(4px); }

/* ══════════════════════════════════════════
   CONTENT PAGE LAYOUT
   ══════════════════════════════════════════ */
.page-container {
  max-width: 900px;
  margin: 0 auto;
  padding: var(--space-2xl) var(--space-xl);
}
.page-header {
  margin-bottom: var(--space-2xl);
  padding-bottom: var(--space-xl);
  border-bottom: 1px solid var(--border-subtle);
}
.page-header .part-label {
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 2px;
  color: var(--accent-purple);
  margin-bottom: var(--space-sm);
}
.page-header h1 { margin-bottom: var(--space-sm); }
.page-header .page-meta {
  display: flex;
  gap: var(--space-lg);
  color: var(--text-muted);
  font-size: 0.875rem;
}

/* Content sections */
.content-section {
  margin-bottom: var(--space-2xl);
}
.content-section h2 {
  color: var(--accent-blue);
  margin-bottom: var(--space-lg);
  padding-bottom: var(--space-sm);
  border-bottom: 2px solid rgba(0, 212, 255, 0.15);
}
.content-section h3 {
  color: var(--text-primary);
  margin: var(--space-xl) 0 var(--space-md);
}
.content-section h4 {
  color: var(--accent-purple);
  margin: var(--space-lg) 0 var(--space-sm);
}

/* ══════════════════════════════════════════
   TABLES
   ══════════════════════════════════════════ */
.styled-table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--space-lg) 0;
  font-size: 0.875rem;
  border-radius: var(--radius-md);
  overflow: hidden;
  border: 1px solid var(--border-subtle);
}
.styled-table thead th {
  background: rgba(124, 58, 237, 0.12);
  color: var(--accent-blue);
  font-weight: 600;
  text-align: left;
  padding: 12px 16px;
  border-bottom: 2px solid var(--border-subtle);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}
.styled-table tbody td {
  padding: 12px 16px;
  border-bottom: 1px solid rgba(255,255,255,0.04);
  color: var(--text-secondary);
}
.styled-table tbody tr:hover {
  background: rgba(0, 212, 255, 0.04);
}
.styled-table tbody tr:last-child td { border-bottom: none; }

/* ══════════════════════════════════════════
   CODE BLOCKS
   ══════════════════════════════════════════ */
code {
  font-family: var(--font-mono);
  font-size: 0.85em;
  background: rgba(124, 58, 237, 0.1);
  padding: 2px 6px;
  border-radius: 4px;
  color: var(--accent-blue);
}
pre {
  background: #0d1117;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  overflow-x: auto;
  margin: var(--space-lg) 0;
  position: relative;
}
pre code {
  background: none;
  padding: 0;
  font-size: 0.82rem;
  line-height: 1.7;
  color: #c9d1d9;
}
.code-label {
  position: absolute;
  top: 8px;
  right: 12px;
  font-size: 0.7rem;
  color: var(--text-muted);
  background: rgba(255,255,255,0.05);
  padding: 2px 8px;
  border-radius: 4px;
}

/* ══════════════════════════════════════════
   SOLUTION TOGGLE
   ══════════════════════════════════════════ */
.solution-block {
  margin: var(--space-lg) 0;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  overflow: hidden;
}
.solution-toggle {
  width: 100%;
  padding: 14px 20px;
  background: rgba(16, 185, 129, 0.08);
  border: none;
  color: var(--accent-green);
  font-family: var(--font-body);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 10px;
  transition: all var(--transition-fast);
}
.solution-toggle:hover { background: rgba(16, 185, 129, 0.14); }
.solution-toggle .arrow {
  transition: transform var(--transition-fast);
  font-size: 0.75rem;
}
.solution-toggle.open .arrow { transform: rotate(90deg); }
.solution-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.5s var(--ease-out), padding 0.3s var(--ease-out);
  background: rgba(16, 185, 129, 0.03);
}
.solution-content.open {
  max-height: 2000px;
  padding: var(--space-lg) var(--space-xl);
}

/* ══════════════════════════════════════════
   CALLOUT / INSIGHT BOX
   ══════════════════════════════════════════ */
.callout {
  padding: var(--space-lg);
  border-radius: var(--radius-md);
  margin: var(--space-lg) 0;
  border-left: 4px solid;
}
.callout-insight {
  background: rgba(0, 212, 255, 0.06);
  border-color: var(--accent-blue);
}
.callout-warning {
  background: rgba(245, 158, 11, 0.06);
  border-color: var(--accent-orange);
}
.callout-tip {
  background: rgba(16, 185, 129, 0.06);
  border-color: var(--accent-green);
}
.callout-title {
  font-weight: 700;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: var(--space-sm);
}
.callout-insight .callout-title { color: var(--accent-blue); }
.callout-warning .callout-title { color: var(--accent-orange); }
.callout-tip .callout-title { color: var(--accent-green); }
.callout p:last-child { margin-bottom: 0; }

/* ══════════════════════════════════════════
   DIAGRAM BOXES (ASCII art replacement)
   ══════════════════════════════════════════ */
.diagram-box {
  background: rgba(124, 58, 237, 0.05);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: var(--space-xl);
  margin: var(--space-lg) 0;
  text-align: center;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--text-secondary);
  line-height: 1.5;
  overflow-x: auto;
  white-space: pre;
}

/* ══════════════════════════════════════════
   NAV (Prev / Next)
   ══════════════════════════════════════════ */
.page-nav {
  display: flex;
  justify-content: space-between;
  gap: var(--space-lg);
  margin-top: var(--space-3xl);
  padding-top: var(--space-xl);
  border-top: 1px solid var(--border-subtle);
}
.page-nav a {
  display: flex;
  flex-direction: column;
  padding: var(--space-md) var(--space-lg);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  max-width: 45%;
}
.page-nav a:hover {
  border-color: var(--border-glow);
  background: var(--bg-card);
}
.page-nav .nav-label {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-muted);
  margin-bottom: 4px;
}
.page-nav .nav-title {
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--accent-blue);
}
.page-nav .next { text-align: right; margin-left: auto; }

/* ══════════════════════════════════════════
   REFERENCES
   ══════════════════════════════════════════ */
.references {
  margin-top: var(--space-2xl);
  padding-top: var(--space-lg);
  border-top: 1px solid var(--border-subtle);
}
.references h3 { color: var(--text-muted); font-size: 1rem; }
.references ol {
  padding-left: var(--space-xl);
  margin-top: var(--space-md);
}
.references li {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: var(--space-sm);
  line-height: 1.6;
}

/* ══════════════════════════════════════════
   TECH STACK PILLS
   ══════════════════════════════════════════ */
.tech-stack {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  justify-content: center;
  margin: var(--space-xl) 0;
}
.tech-pill {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border-radius: 50px;
  font-size: 0.82rem;
  font-weight: 500;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
}

/* ══════════════════════════════════════════
   ANIMATIONS
   ══════════════════════════════════════════ */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  animation: fadeInUp 0.6s var(--ease-out) forwards;
}
@keyframes fadeInUp {
  to { opacity: 1; transform: translateY(0); }
}
.stagger-1 { animation-delay: 0.05s; }
.stagger-2 { animation-delay: 0.1s; }
.stagger-3 { animation-delay: 0.15s; }
.stagger-4 { animation-delay: 0.2s; }
.stagger-5 { animation-delay: 0.25s; }
.stagger-6 { animation-delay: 0.3s; }
.stagger-7 { animation-delay: 0.35s; }

/* ══════════════════════════════════════════
   UTILITIES
   ══════════════════════════════════════════ */
.container {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 var(--space-xl);
}
.text-center { text-align: center; }
.text-gradient {
  background: var(--gradient-accent);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.mt-1 { margin-top: var(--space-md); }
.mt-2 { margin-top: var(--space-xl); }
.mt-3 { margin-top: var(--space-2xl); }
.mb-1 { margin-bottom: var(--space-md); }
.mb-2 { margin-bottom: var(--space-xl); }

/* ── Responsive ── */
@media (max-width: 768px) {
  .card-grid { grid-template-columns: 1fr; }
  .hero { padding: var(--space-2xl) var(--space-md); }
  .page-container { padding: var(--space-xl) var(--space-md); }
  .hero-meta { flex-direction: column; align-items: center; }
  .page-nav { flex-direction: column; }
  .page-nav a { max-width: 100%; }
  .footer-inner { flex-direction: column; }
}
@media (max-width: 480px) {
  .card-grid { grid-template-columns: 1fr; padding: 0 var(--space-md); }
  .styled-table { font-size: 0.78rem; }
  .styled-table thead th,
  .styled-table tbody td { padding: 8px 10px; }
}