/* ── TC4U Design Tokens ─────────────────────────────────────────────────── */
:root {
  --navy-900: #1a1a2e;
  --navy-800: #16213e;
  --navy-700: #1e3a5f;
  --blue-600: #2563eb;
  --blue-700: #1d4ed8;
  --blue-400: #60a5fa;
  --green-700: #15803d;
  --green-600: #059669;
  --amber-500: #f59e0b;
  --red-600: #dc2626;
  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-400: #9ca3af;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2937;
  --gray-900: #111827;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --max-width: 860px;
}

/* ── Reset ──────────────────────────────────────────────────────────────── */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
body {
  font-family: var(--font-sans);
  background: var(--gray-100);
  color: var(--gray-900);
  font-size: 16px;
  line-height: 1.7;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ── Header ─────────────────────────────────────────────────────────────── */
.site-header {
  background: var(--navy-900);
  padding: 16px 0;
  position: sticky;
  top: 0;
  z-index: 100;
}
.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.header-logo {
  height: 28px;
  width: auto;
}
.header-nav { display: flex; gap: 24px; align-items: center; }
.header-nav a {
  color: #94a3b8;
  text-decoration: none;
  font-size: 14px;
  font-weight: 500;
  transition: color 0.2s;
}
.header-nav a:hover { color: #fff; }
.header-cta {
  background: var(--blue-600) !important;
  color: #fff !important;
  padding: 8px 18px;
  border-radius: 8px;
  font-weight: 600 !important;
  font-size: 13px !important;
}
.header-cta:hover { background: var(--blue-700) !important; }

/* ── Main content ───────────────────────────────────────────────────────── */
.page-content {
  flex: 1;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 48px 24px 80px;
  width: 100%;
}

/* ── Breadcrumbs ────────────────────────────────────────────────────────── */
.breadcrumbs {
  font-size: 13px;
  color: var(--gray-400);
  margin-bottom: 24px;
}
.breadcrumbs a { color: var(--blue-600); text-decoration: none; }
.breadcrumbs a:hover { text-decoration: underline; }
.breadcrumbs span { margin: 0 6px; }

/* ── Typography ─────────────────────────────────────────────────────────── */
.page-content h1 {
  font-size: 32px;
  font-weight: 800;
  color: var(--gray-900);
  margin-bottom: 16px;
  line-height: 1.2;
}
.page-content h2 {
  font-size: 22px;
  font-weight: 700;
  color: var(--gray-900);
  margin-top: 40px;
  margin-bottom: 12px;
  line-height: 1.3;
}
.page-content h3 {
  font-size: 18px;
  font-weight: 600;
  color: var(--gray-800);
  margin-top: 32px;
  margin-bottom: 8px;
}
.page-content p { margin-bottom: 16px; color: var(--gray-700); }
.page-content ul, .page-content ol {
  margin-bottom: 16px;
  padding-left: 24px;
  color: var(--gray-700);
}
.page-content li { margin-bottom: 6px; }
.page-content a { color: var(--blue-600); text-decoration: none; }
.page-content a:hover { text-decoration: underline; }
.page-content blockquote {
  border-left: 3px solid var(--blue-600);
  padding: 12px 20px;
  margin: 20px 0;
  background: #eff6ff;
  border-radius: 0 8px 8px 0;
  color: var(--gray-700);
}
.page-content table {
  width: 100%;
  border-collapse: collapse;
  margin: 20px 0;
  font-size: 14px;
}
.page-content th {
  background: var(--gray-100);
  font-weight: 600;
  text-align: left;
  padding: 10px 14px;
  border-bottom: 2px solid var(--gray-200);
}
.page-content td {
  padding: 10px 14px;
  border-bottom: 1px solid var(--gray-200);
}
.page-content code {
  background: var(--gray-100);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 14px;
}

/* ── Figure citation ────────────────────────────────────────────────────── */
.fig-value { font-weight: 700; color: var(--navy-700); }
.fig-cite { font-size: 12px; color: var(--gray-400); margin-left: 4px; }

/* ── Footer ─────────────────────────────────────────────────────────────── */
.site-footer {
  background: var(--gray-900);
  color: var(--gray-400);
  padding: 40px 0;
  font-size: 13px;
}
.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}
.footer-top {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 24px;
  flex-wrap: wrap;
  gap: 24px;
}
.footer-brand { color: #fff; font-weight: 700; font-size: 15px; margin-bottom: 8px; }
.footer-tagline { color: var(--gray-400); font-size: 13px; }
.footer-links { display: flex; gap: 20px; flex-wrap: wrap; }
.footer-links a { color: var(--gray-400); text-decoration: none; }
.footer-links a:hover { color: #fff; }
.footer-bottom {
  border-top: 1px solid rgba(255,255,255,0.1);
  padding-top: 20px;
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px;
}

/* ── Responsive ─────────────────────────────────────────────────────────── */
@media (max-width: 640px) {
  .page-content h1 { font-size: 26px; }
  .page-content h2 { font-size: 20px; }
  .header-nav { gap: 16px; }
  .footer-top { flex-direction: column; }
}

/* ── Blog cards ─────────────────────────────────────────────────────────── */
.blog-grid {
  display: flex;
  flex-direction: column;
  gap: 20px;
  margin-top: 24px;
}
.blog-card {
  background: #fff;
  border: 1px solid var(--gray-200);
  border-radius: 12px;
  padding: 28px;
  text-decoration: none !important;
  display: block;
  transition: border-color 0.2s, box-shadow 0.2s;
  color: inherit !important;
}
.blog-card:hover {
  border-color: var(--blue-600);
  box-shadow: 0 2px 12px rgba(37, 99, 235, 0.08);
  text-decoration: none !important;
}
.page-content .blog-card-title {
  font-size: 18px;
  font-weight: 700;
  color: var(--gray-900);
  margin: 0 0 8px 0;
  line-height: 1.3;
}
.blog-card:hover .blog-card-title { color: var(--blue-600); }
.page-content .blog-card-desc {
  font-size: 14px;
  color: var(--gray-500);
  line-height: 1.6;
  margin: 0 0 12px 0;
}
.page-content .blog-card-arrow {
  font-size: 13px;
  font-weight: 600;
  color: var(--blue-600);
  margin: 0;
}