/* =====================================================================
   AI4SC HUB — Design System v3 (Blackstone-Inspired)
   Premium institutional aesthetic: serif authority, gold accent,
   generous whitespace, typographic-first hierarchy
   ===================================================================== */

/* ===== GOOGLE FONTS ===== */
@import url('https://fonts.googleapis.com/css2?family=Playfair+Display:ital,wght@0,400;0,500;0,600;0,700;1,400;1,600&family=Inter:wght@300;400;500;600&family=JetBrains+Mono:wght@400;500&display=swap');

/* ===== DESIGN TOKENS ===== */
:root {
  /* Surfaces */
  --s-base:        #FAFAF8;   /* warm off-white */
  --s-canvas:      #FFFFFF;
  --s-ink:         #141410;   /* near-black with warmth */
  --s-ink-soft:    #2A2A24;
  --s-section:     #F2EFE8;   /* warm panel */
  --s-dark:        #141410;   /* dark sections */
  --s-dark-raised: #1E1E18;

  /* Typography */
  --t-primary:  #141410;
  --t-body:     #3A3A32;
  --t-muted:    #6B6B5E;
  --t-dim:      #9B9B8E;
  --t-inverse:  #F5F0E8;
  --t-inverse-muted: #B8B0A0;

  /* Accent — institutional gold */
  --a-gold:       #B8965E;
  --a-gold-light: #D4B07A;
  --a-gold-pale:  #F0E6D0;
  --a-gold-dark:  #8B6E3E;

  /* Borders */
  --b-default: rgba(20,20,16,0.10);
  --b-soft:    rgba(20,20,16,0.06);
  --b-gold:    rgba(184,150,94,0.30);
  --b-dark:    rgba(255,255,255,0.10);

  /* Type */
  --f-display: 'Playfair Display', Georgia, 'Times New Roman', serif;
  --f-body:    'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --f-mono:    'JetBrains Mono', 'Courier New', monospace;

  /* Radius */
  --r-sm: 2px;
  --r-md: 4px;
  --r-lg: 6px;

  /* Motion */
  --ease: cubic-bezier(0.25, 0.0, 0.0, 1.0);
  --dur-fast: 160ms;
  --dur-base: 280ms;
}

/* ===== RESET ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; text-rendering: optimizeLegibility; -webkit-font-smoothing: antialiased; }
body { font-family: var(--f-body); background: var(--s-base); color: var(--t-primary); line-height: 1.6; overflow-x: hidden; }
a { text-decoration: none; color: inherit; }
img { max-width: 100%; display: block; }
button { font-family: inherit; cursor: pointer; }

/* ===== LAYOUT ===== */
.wrap {
  max-width: 1320px;
  margin: 0 auto;
  padding: 0 clamp(24px, 5vw, 80px);
}

.wrap-narrow {
  max-width: 880px;
  margin: 0 auto;
  padding: 0 clamp(24px, 5vw, 80px);
}

/* ===== NAVIGATION ===== */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 500;
  background: rgba(250,250,248,0.95);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--b-default);
  transition: border-color var(--dur-base) var(--ease);
}

.nav-inner {
  display: flex;
  align-items: center;
  height: 72px;
  gap: 40px;
}

.brand {
  display: flex;
  flex-direction: column;
  gap: 2px;
  flex-shrink: 0;
  text-decoration: none;
}

.brand-wordmark {
  font-family: var(--f-display);
  font-size: 18px;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: var(--t-primary);
  line-height: 1;
}

.brand-tagline {
  font-size: 9px;
  font-weight: 500;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--a-gold);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 0;
  flex: 1;
  justify-content: center;
}

.nav-links a {
  padding: 8px 18px;
  font-size: 13px;
  font-weight: 400;
  letter-spacing: 0.04em;
  color: var(--t-body);
  transition: color var(--dur-fast) var(--ease);
  position: relative;
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: 4px;
  left: 18px;
  right: 18px;
  height: 1px;
  background: var(--a-gold);
  transform: scaleX(0);
  transition: transform var(--dur-base) var(--ease);
  transform-origin: left;
}

.nav-links a:hover { color: var(--t-primary); }
.nav-links a:hover::after, .nav-links a.active::after { transform: scaleX(1); }
.nav-links a.active { color: var(--t-primary); font-weight: 500; }

.nav-actions { display: flex; align-items: center; gap: 16px; flex-shrink: 0; }

.btn-text-sm {
  font-size: 13px;
  font-weight: 400;
  letter-spacing: 0.06em;
  color: var(--t-muted);
  transition: color var(--dur-fast) var(--ease);
}

.btn-text-sm:hover { color: var(--t-primary); }

.btn-cta {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 22px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.10em;
  text-transform: uppercase;
  color: var(--s-canvas);
  background: var(--s-ink);
  border: 1px solid var(--s-ink);
  transition: all var(--dur-base) var(--ease);
}

.btn-cta:hover {
  background: var(--a-gold);
  border-color: var(--a-gold);
}

/* ===== SECTION COMMONS ===== */
.sec { padding: 100px 0; }
.sec-lg { padding: 140px 0; }
.sec-sm { padding: 60px 0; }
.sec-dark { background: var(--s-dark); color: var(--t-inverse); }
.sec-warm { background: var(--s-section); }

.rule {
  height: 1px;
  background: var(--b-default);
  border: none;
  margin: 0;
}

.rule-gold {
  height: 1px;
  background: var(--a-gold);
  border: none;
  width: 48px;
  margin: 0;
}

/* Eyebrow */
.eyebrow {
  display: inline-block;
  font-size: 10px;
  font-weight: 600;
  letter-spacing: 0.20em;
  text-transform: uppercase;
  color: var(--a-gold);
  margin-bottom: 20px;
}

/* Display headings */
.h-display {
  font-family: var(--f-display);
  font-size: clamp(44px, 6vw, 80px);
  font-weight: 500;
  letter-spacing: -0.01em;
  line-height: 1.05;
  color: var(--t-primary);
}

.h-section {
  font-family: var(--f-display);
  font-size: clamp(32px, 4vw, 52px);
  font-weight: 500;
  letter-spacing: -0.01em;
  line-height: 1.1;
  color: var(--t-primary);
}

.h-card {
  font-family: var(--f-display);
  font-size: clamp(20px, 2.5vw, 26px);
  font-weight: 500;
  line-height: 1.2;
  color: var(--t-primary);
}

.lead {
  font-size: clamp(16px, 1.5vw, 19px);
  line-height: 1.75;
  color: var(--t-body);
  font-weight: 300;
}

/* Dark section typography overrides */
.sec-dark .eyebrow { color: var(--a-gold-light); }
.sec-dark .h-display, .sec-dark .h-section, .sec-dark .h-card { color: var(--t-inverse); }
.sec-dark .lead { color: var(--t-inverse-muted); }

/* ===== BUTTONS ===== */
.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 14px 28px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--s-canvas);
  background: var(--s-ink);
  border: 1px solid var(--s-ink);
  transition: all var(--dur-base) var(--ease);
}

.btn-primary:hover {
  background: var(--a-gold);
  border-color: var(--a-gold);
}

.btn-primary.btn-lg { padding: 17px 36px; font-size: 13px; }

.btn-outline {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 14px 28px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--t-primary);
  background: transparent;
  border: 1px solid var(--b-default);
  transition: all var(--dur-base) var(--ease);
}

.btn-outline:hover {
  border-color: var(--t-primary);
  background: var(--s-ink);
  color: var(--t-inverse);
}

.btn-outline.btn-lg { padding: 17px 36px; font-size: 13px; }

.btn-outline-inv {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 14px 28px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--t-inverse);
  background: transparent;
  border: 1px solid rgba(255,255,255,0.25);
  transition: all var(--dur-base) var(--ease);
}

.btn-outline-inv:hover {
  background: var(--a-gold);
  border-color: var(--a-gold);
}

.btn-outline-inv.btn-lg { padding: 17px 36px; font-size: 13px; }

/* Arrow link */
.arrow-link {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.10em;
  text-transform: uppercase;
  color: var(--a-gold);
  transition: gap var(--dur-fast) var(--ease);
}

.arrow-link:hover { gap: 14px; }

/* ===== FOOTER ===== */
.site-footer {
  background: var(--s-ink);
  color: var(--t-inverse);
  padding: 72px 0 40px;
}

.footer-top {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 80px;
  padding-bottom: 56px;
  border-bottom: 1px solid var(--b-dark);
  margin-bottom: 48px;
}

.footer-brand {}

.footer-brand-name {
  font-family: var(--f-display);
  font-size: 20px;
  font-weight: 600;
  letter-spacing: 0.04em;
  color: var(--t-inverse);
  margin-bottom: 4px;
}

.footer-brand-tag {
  font-size: 9px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--a-gold-light);
  margin-bottom: 20px;
}

.footer-brand-desc {
  font-size: 13px;
  line-height: 1.75;
  color: var(--t-inverse-muted);
  max-width: 240px;
}

.footer-nav {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 40px;
}

.footer-col h4 {
  font-size: 9px;
  font-weight: 700;
  letter-spacing: 0.20em;
  text-transform: uppercase;
  color: var(--a-gold-light);
  margin-bottom: 20px;
}

.footer-col a {
  display: block;
  font-size: 13px;
  color: var(--t-inverse-muted);
  padding: 5px 0;
  transition: color var(--dur-fast) var(--ease);
}

.footer-col a:hover { color: var(--t-inverse); }

.footer-bottom {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
}

.footer-copy {
  font-size: 12px;
  color: var(--t-inverse-muted);
  letter-spacing: 0.04em;
}

.footer-social { display: flex; gap: 24px; }

.footer-social a {
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--t-inverse-muted);
  transition: color var(--dur-fast) var(--ease);
}

.footer-social a:hover { color: var(--a-gold-light); }

/* ===== RESPONSIVE ===== */
@media (max-width: 1024px) {
  .footer-top { grid-template-columns: 1fr; gap: 48px; }
  .footer-nav { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 768px) {
  .nav-links { display: none; }
  .btn-text-sm { display: none; }
  .nav-inner { gap: 16px; justify-content: space-between; }
  .brand { min-width: 0; }
  .brand-tagline { display: none; }
  .btn-cta { padding: 9px 14px; letter-spacing: 0.06em; }
  .footer-nav { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 480px) {
  .footer-nav { grid-template-columns: 1fr; }
}