/* CSS Variables */
:root {
  --primary: #0f3fb8;
  --primary-dark: #0a2c82;
  --secondary: #0b1220;
  --accent: #f97316;
  --text: #1e293b;
  --text-light: #475569;
  --bg: #f8fafc;
  --bg-alt: #ffffff;
  --border: #dbe4f0;
  --success: #059669;
  --shadow: 0 10px 25px rgba(15, 23, 42, 0.08);
  --shadow-lg: 0 18px 45px rgba(15, 23, 42, 0.14);
  --radius: 12px;
  --transition: all 0.25s ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Source Serif 4', Georgia, serif;
  line-height: 1.7;
  color: var(--text);
  background: radial-gradient(circle at 10% -20%, #e9f0ff 0, transparent 35%), var(--bg);
}

h1, h2, h3, h4, .logo, .nav-menu a, .cta-btn {
  font-family: 'Manrope', system-ui, -apple-system, sans-serif;
  letter-spacing: -0.02em;
}

a {
  text-decoration: none;
  color: inherit;
}

ul {
  list-style: none;
}

img {
  max-width: 100%;
  height: auto;
}

/* Container */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

/* Header */
.header {
  background: rgba(248, 250, 252, 0.88);
  border-bottom: 1px solid rgba(15, 63, 184, 0.08);
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(10px);
}

.nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 70px;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--secondary);
}

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

.nav-menu {
  display: flex;
  gap: 30px;
}

.nav-menu a {
  font-weight: 500;
  color: var(--text);
  transition: var(--transition);
}

.nav-menu a:hover {
  color: var(--primary);
}

.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 5px;
}

.menu-toggle span {
  width: 25px;
  height: 3px;
  background: var(--secondary);
  border-radius: 2px;
}

/* Hero Section */
.hero {
  background:
    radial-gradient(circle at 15% 10%, rgba(249, 115, 22, 0.25), transparent 30%),
    radial-gradient(circle at 80% 0%, rgba(96, 165, 250, 0.35), transparent 40%),
    linear-gradient(130deg, var(--secondary) 0%, #16243e 55%, #1d3c89 100%);
  color: white;
  padding: 108px 0 92px;
  text-align: center;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.4rem);
  margin-bottom: 18px;
  font-weight: 800;
  max-width: 860px;
  margin-left: auto;
  margin-right: auto;
  line-height: 1.08;
}

.hero p {
  font-size: 1.2rem;
  opacity: 0.9;
  margin-bottom: 40px;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.search-box {
  display: flex;
  max-width: 500px;
  margin: 0 auto;
  background: white;
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.search-box input {
  flex: 1;
  padding: 15px 20px;
  border: none;
  font-size: 1rem;
  outline: none;
}

.search-box button {
  padding: 15px 30px;
  background: var(--primary);
  color: white;
  border: none;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}

.search-box button:hover {
  background: var(--primary-dark);
}

/* Clusters Section */
.clusters {
  padding: 80px 20px;
}

.clusters h2 {
  text-align: center;
  font-size: 2rem;
  margin-bottom: 40px;
  color: var(--secondary);
}

.clusters-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 30px;
}

.cluster-card {
  background: linear-gradient(180deg, #fff 0%, #f8fbff 100%);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 30px;
  transition: var(--transition);
  display: block;
  box-shadow: var(--shadow);
}

.cluster-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-lg);
  border-color: rgba(15, 63, 184, 0.4);
}

.cluster-icon {
  font-size: 3rem;
  margin-bottom: 20px;
}

.cluster-card h3 {
  font-size: 1.25rem;
  margin-bottom: 10px;
  color: var(--secondary);
}

.cluster-card p {
  color: var(--text-light);
  margin-bottom: 15px;
}

.cluster-link {
  color: var(--primary);
  font-weight: 500;
}

.cluster-card:hover .cluster-link {
  text-decoration: underline;
}

/* Featured Articles */
.featured-articles {
  background: var(--bg-alt);
  padding: 80px 20px;
}

.featured-articles h2 {
  text-align: center;
  font-size: 2rem;
  margin-bottom: 40px;
  color: var(--secondary);
}

.articles-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 30px;
}

.article-card {
  background: #ffffff;
  border-radius: 16px;
  padding: 25px;
  box-shadow: var(--shadow);
  transition: var(--transition);
  border: 1px solid rgba(15, 63, 184, 0.07);
}

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

.article-card h3 {
  font-size: 1.1rem;
  margin-bottom: 10px;
}

.article-card h3 a {
  color: var(--secondary);
  transition: var(--transition);
}

.article-card h3 a:hover {
  color: var(--primary);
}

.article-card p {
  color: var(--text-light);
  font-size: 0.95rem;
  margin-bottom: 15px;
}

.read-time {
  font-size: 0.85rem;
  color: var(--text-light);
  background: var(--bg-alt);
  padding: 4px 10px;
  border-radius: 20px;
}

/* About Section */
.about {
  padding: 80px 20px;
  text-align: center;
  max-width: 800px;
  margin: 0 auto;
}

.about h2 {
  font-size: 2rem;
  margin-bottom: 20px;
  color: var(--secondary);
}

.about p {
  margin-bottom: 15px;
  color: var(--text);
}

/* Footer */
.footer {
  background: var(--secondary);
  color: white;
  padding: 60px 0 0;
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 40px;
  margin-bottom: 40px;
}

.footer-col h4 {
  font-size: 1.1rem;
  margin-bottom: 20px;
  color: white;
}

.footer-col ul li {
  margin-bottom: 10px;
}

.footer-col a {
  color: rgba(255, 255, 255, 0.7);
  transition: var(--transition);
}

.footer-col a:hover {
  color: white;
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  padding: 20px 0;
  text-align: center;
  color: rgba(255, 255, 255, 0.6);
  font-size: 0.9rem;
}

/* Page Header (for inner pages) */
.page-header {
  background: linear-gradient(135deg, var(--secondary) 0%, #1e293b 100%);
  color: white;
  padding: 60px 0;
  text-align: center;
}

.page-header h1 {
  font-size: 2rem;
  margin-bottom: 10px;
}

.page-header p {
  opacity: 0.9;
  max-width: 600px;
  margin: 0 auto;
}

.breadcrumb {
  padding: 15px 20px;
  background: var(--bg-alt);
  font-size: 0.9rem;
  color: var(--text-light);
}

.breadcrumb a {
  color: var(--primary);
}

.breadcrumb span {
  margin: 0 10px;
}

/* Content Page */
.content-page {
  padding: 60px 20px;
  max-width: 800px;
  margin: 0 auto;
}

.content-page h1 {
  font-size: 2rem;
  margin-bottom: 20px;
  color: var(--secondary);
}

.content-page h2 {
  font-size: 1.5rem;
  margin: 40px 0 20px;
  color: var(--secondary);
}

.content-page h3 {
  font-size: 1.25rem;
  margin: 30px 0 15px;
  color: var(--secondary);
}

.content-page p {
  margin-bottom: 15px;
  line-height: 1.85;
}

.meta {
  font-family: 'Manrope', sans-serif;
  font-size: 0.9rem;
  color: var(--text-light);
  margin-bottom: 24px;
}

strong {
  color: #0f172a;
}

.content-page ul, .content-page ol {
  margin-bottom: 20px;
  padding-left: 25px;
}

.content-page li {
  margin-bottom: 10px;
}

.content-page .highlight-box {
  background: #eff6ff;
  border-left: 4px solid var(--primary);
  padding: 20px;
  margin: 30px 0;
  border-radius: 0 var(--radius) var(--radius) 0;
}

.content-page .warning-box {
  background: #fef3c7;
  border-left: 4px solid var(--accent);
  padding: 20px;
  margin: 30px 0;
  border-radius: 0 var(--radius) var(--radius) 0;
}

.content-page table {
  width: 100%;
  border-collapse: collapse;
  margin: 30px 0;
}

.content-page th, .content-page td {
  padding: 12px 15px;
  text-align: left;
  border: 1px solid var(--border);
}

.content-page th {
  background: var(--bg-alt);
  font-weight: 600;
}

.content-page blockquote {
  border-left: 4px solid var(--primary);
  padding-left: 20px;
  margin: 30px 0;
  font-style: italic;
  color: var(--text-light);
}

/* Author Box */
.author-box {
  background: var(--bg-alt);
  padding: 25px;
  border-radius: var(--radius);
  margin: 40px 0;
  display: flex;
  align-items: center;
  gap: 20px;
}

.author-avatar {
  width: 60px;
  height: 60px;
  background: var(--primary);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 1.5rem;
  font-weight: 700;
}

.author-info h4 {
  margin-bottom: 5px;
  color: var(--secondary);
}

.author-info p {
  font-size: 0.9rem;
  color: var(--text-light);
  margin: 0;
}

/* Related Articles */
.related-articles {
  background: var(--bg-alt);
  padding: 60px 20px;
}

.related-articles h2 {
  text-align: center;
  font-size: 1.5rem;
  margin-bottom: 40px;
  color: var(--secondary);
}

.related-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 25px;
  max-width: 1000px;
  margin: 0 auto;
}

/* CTA Section */
.cta-section {
  background: var(--primary);
  color: white;
  padding: 60px 20px;
  text-align: center;
}

.cta-section h2 {
  margin-bottom: 15px;
}

.cta-section p {
  margin-bottom: 25px;
  opacity: 0.9;
}

.cta-btn {
  display: inline-block;
  background: white;
  color: var(--primary);
  padding: 15px 30px;
  border-radius: var(--radius);
  font-weight: 600;
  transition: var(--transition);
}

.cta-btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

/* FAQ Section */
.faq-section {
  padding: 60px 20px;
  max-width: 800px;
  margin: 0 auto;
}

.faq-section h2 {
  text-align: center;
  font-size: 1.5rem;
  margin-bottom: 40px;
  color: var(--secondary);
}

.faq-item {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 15px;
  overflow: hidden;
}

.faq-question {
  padding: 20px;
  background: var(--bg);
  cursor: pointer;
  font-weight: 500;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: var(--transition);
}

.faq-question:hover {
  background: var(--bg-alt);
}

.faq-question::after {
  content: '+';
  font-size: 1.5rem;
  color: var(--primary);
}

.faq-item.active .faq-question::after {
  content: '-';
}

.faq-answer {
  padding: 0 20px;
  max-height: 0;
  overflow: hidden;
  transition: all 0.3s ease;
}

.faq-item.active .faq-answer {
  padding: 20px;
  max-height: 500px;
}

/* Responsive */
@media (max-width: 768px) {
  .nav-menu {
    display: none;
    position: absolute;
    top: 70px;
    left: 0;
    right: 0;
    background: var(--bg);
    flex-direction: column;
    padding: 20px;
    gap: 15px;
    border-bottom: 1px solid var(--border);
    box-shadow: var(--shadow);
  }

  .nav-menu.active {
    display: flex;
  }

  .menu-toggle {
    display: flex;
  }

  .hero h1 {
    font-size: 1.8rem;
  }

  .hero p {
    font-size: 1rem;
  }

  .search-box {
    flex-direction: column;
  }

  .search-box button {
    width: 100%;
  }

  .clusters-grid, .articles-grid {
    grid-template-columns: 1fr;
  }

  .footer-grid {
    grid-template-columns: 1fr;
  }

  .author-box {
    flex-direction: column;
    text-align: center;
  }
}