/* ==========================================================================
   冲上云霄 (csyxjc.homes) - Design System & Modern Gradient Theme
   Design Style: Borderless Transparency / Breathable Negative Space (无界通透 / 呼吸留白)
   ========================================================================== */

:root {
  --bg-dark: #070913;
  --bg-card: rgba(255, 255, 255, 0.03);
  --bg-card-hover: rgba(255, 255, 255, 0.06);
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --accent-blue: #38bdf8;
  --accent-purple: #8b5cf6;
  --accent-pink: #ec4899;
  --gradient-primary: linear-gradient(135deg, #6366f1 0%, #8b5cf6 50%, #d946ef 100%);
  --gradient-glow: radial-gradient(circle, rgba(99, 102, 241, 0.15) 0%, rgba(7, 9, 19, 0) 70%);
  --font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --radius-lg: 24px;
  --radius-md: 16px;
  --radius-sm: 10px;
  --transition-fast: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
  --max-width: 1200px;
}

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

html {
  scroll-behavior: smooth;
  font-family: var(--font-family);
  background-color: var(--bg-dark);
  color: var(--text-primary);
  line-height: 1.6;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

body {
  overflow-x: hidden;
  position: relative;
  background: radial-gradient(circle at 50% -20%, rgba(99, 102, 241, 0.12) 0%, transparent 60%),
              radial-gradient(circle at 90% 40%, rgba(236, 72, 153, 0.08) 0%, transparent 50%),
              radial-gradient(circle at 10% 80%, rgba(56, 189, 248, 0.08) 0%, transparent 50%),
              var(--bg-dark);
  min-height: 100vh;
}

/* Helper Utilities */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

.text-gradient {
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  display: inline-block;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 16px;
  border-radius: 100px;
  background: rgba(99, 102, 241, 0.1);
  border: 1px solid rgba(99, 102, 241, 0.2);
  color: var(--accent-blue);
  font-size: 0.875rem;
  font-weight: 600;
  letter-spacing: 0.5px;
}

/* Dynamic Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 14px 28px;
  border-radius: 100px;
  font-size: 1rem;
  font-weight: 600;
  text-decoration: none;
  transition: var(--transition-fast);
  cursor: pointer;
  white-space: nowrap;
  border: none;
}

.btn-primary {
  background: var(--gradient-primary);
  color: #ffffff;
  box-shadow: 0 10px 30px -10px rgba(99, 102, 241, 0.5);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 15px 35px -5px rgba(139, 92, 246, 0.6);
}

.btn-secondary {
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-primary);
  backdrop-filter: blur(10px);
}

.btn-secondary:hover {
  background: rgba(255, 255, 255, 0.12);
  transform: translateY(-2px);
}

/* Fixed Navbar */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 1000;
  background: rgba(7, 9, 19, 0.75);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  padding: 16px 0;
  transition: var(--transition-fast);
}

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

.brand-logo {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 1.35rem;
  font-weight: 800;
  color: var(--text-primary);
  text-decoration: none;
}

.brand-icon {
  width: 36px;
  height: 36px;
  background: var(--gradient-primary);
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: 32px;
  list-style: none;
}

.nav-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 500;
  transition: var(--transition-fast);
}

.nav-link:hover {
  color: var(--text-primary);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 12px;
}

.nav-actions .btn {
  padding: 10px 20px;
  font-size: 0.875rem;
}

/* Hero Section */
.hero {
  padding: 180px 0 100px;
  text-align: center;
  position: relative;
}

.hero-title {
  font-size: 3.5rem;
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -1px;
  margin: 24px 0;
  max-width: 900px;
  margin-left: auto;
  margin-right: auto;
}

.hero-subtitle {
  font-size: 1.2rem;
  color: var(--text-secondary);
  max-width: 720px;
  margin: 0 auto 36px;
  font-weight: 400;
  line-height: 1.7;
}

.hero-actions {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  margin-bottom: 48px;
}

.hero-stats {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 48px;
  margin-top: 60px;
  padding-top: 40px;
}

.stat-item {
  text-align: center;
}

.stat-num {
  font-size: 2.2rem;
  font-weight: 800;
  color: var(--text-primary);
  display: block;
}

.stat-label {
  font-size: 0.875rem;
  color: var(--text-muted);
}

/* Core Advantages */
.section {
  padding: 100px 0;
}

.section-header {
  text-align: center;
  max-width: 650px;
  margin: 0 auto 64px;
}

.section-title {
  font-size: 2.25rem;
  font-weight: 700;
  margin-top: 16px;
  letter-spacing: -0.5px;
}

.section-desc {
  color: var(--text-secondary);
  font-size: 1.05rem;
  margin-top: 12px;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 32px;
}

.feature-card {
  background: var(--bg-card);
  padding: 40px 32px;
  border-radius: var(--radius-lg);
  backdrop-filter: blur(12px);
  transition: var(--transition-fast);
  position: relative;
  overflow: hidden;
}

.feature-card:hover {
  background: var(--bg-card-hover);
  transform: translateY(-6px);
}

.feature-icon {
  width: 56px;
  height: 56px;
  border-radius: 16px;
  background: rgba(99, 102, 241, 0.12);
  color: var(--accent-blue);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 24px;
}

.feature-card h3 {
  font-size: 1.35rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.feature-card p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.7;
}

/* Ecosystem / Streaming & AI Section */
.eco-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 20px;
}

.eco-card {
  background: var(--bg-card);
  padding: 24px;
  border-radius: var(--radius-md);
  text-align: center;
  transition: var(--transition-fast);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.eco-card:hover {
  background: var(--bg-card-hover);
  transform: translateY(-4px);
}

.eco-icon {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.eco-card span {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--text-primary);
}

.eco-card small {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* Pricing Table */
.pricing-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}

.pricing-card {
  background: var(--bg-card);
  padding: 40px 28px;
  border-radius: var(--radius-lg);
  backdrop-filter: blur(12px);
  display: flex;
  flex-direction: column;
  transition: var(--transition-fast);
  position: relative;
}

.pricing-card.featured {
  background: linear-gradient(180deg, rgba(99, 102, 241, 0.15) 0%, rgba(255, 255, 255, 0.03) 100%);
  box-shadow: 0 0 40px rgba(99, 102, 241, 0.15);
}

.pricing-badge {
  position: absolute;
  top: 20px;
  right: 20px;
  font-size: 0.75rem;
  background: var(--gradient-primary);
  color: #fff;
  padding: 4px 12px;
  border-radius: 100px;
  font-weight: 600;
}

.pricing-plan {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.pricing-price {
  font-size: 2.5rem;
  font-weight: 800;
  margin-bottom: 4px;
}

.pricing-period {
  font-size: 0.875rem;
  color: var(--text-muted);
  margin-bottom: 24px;
}

.pricing-features {
  list-style: none;
  margin-bottom: 32px;
  flex-grow: 1;
}

.pricing-features li {
  font-size: 0.9rem;
  color: var(--text-secondary);
  padding: 8px 0;
  display: flex;
  align-items: center;
  gap: 8px;
}

.pricing-features svg {
  color: #10b981;
  flex-shrink: 0;
}

/* FAQ Details/Summary Accordion (No JS Pure CSS) */
.faq-list {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.faq-item {
  background: var(--bg-card);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: var(--transition-fast);
}

.faq-item summary {
  padding: 24px;
  font-weight: 600;
  font-size: 1.05rem;
  cursor: pointer;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  user-select: none;
}

.faq-item summary::-webkit-details-marker {
  display: none;
}

.faq-icon-chevron {
  transition: transform 0.3s ease;
  width: 20px;
  height: 20px;
  color: var(--accent-blue);
}

.faq-item[open] summary .faq-icon-chevron {
  transform: rotate(180deg);
}

.faq-content {
  padding: 0 24px 24px 24px;
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.7;
}

/* User Reviews Carousel / Grid */
.reviews-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  margin-top: 48px;
}

.review-card {
  background: var(--bg-card);
  padding: 28px;
  border-radius: var(--radius-lg);
}

.review-stars {
  color: #f59e0b;
  margin-bottom: 12px;
  display: flex;
  gap: 4px;
}

.review-text {
  font-size: 0.925rem;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 20px;
}

.review-author {
  display: flex;
  align-items: center;
  gap: 12px;
}

.avatar {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--gradient-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.9rem;
}

.author-info h4 {
  font-size: 0.9rem;
  font-weight: 600;
}

.author-info span {
  font-size: 0.775rem;
  color: var(--text-muted);
}

/* Recommended News / Articles Section */
.articles-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.article-card {
  background: var(--bg-card);
  border-radius: var(--radius-md);
  padding: 28px;
  display: flex;
  flex-direction: column;
  transition: var(--transition-fast);
  text-decoration: none;
  color: inherit;
}

.article-card:hover {
  background: var(--bg-card-hover);
  transform: translateY(-4px);
}

.article-category {
  font-size: 0.8rem;
  color: var(--accent-blue);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 8px;
}

.article-card h3 {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 12px;
  line-height: 1.4;
}

.article-card p {
  color: var(--text-secondary);
  font-size: 0.875rem;
  line-height: 1.6;
  margin-bottom: 16px;
  flex-grow: 1;
}

.article-meta {
  font-size: 0.8rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

/* Footer (Mandatory 4 Links) */
.footer {
  background: rgba(4, 6, 13, 0.95);
  padding: 60px 0 40px;
  border-top: 1px solid rgba(255, 255, 255, 0.03);
  margin-top: 100px;
  text-align: center;
}

.footer-nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 32px;
  margin-bottom: 32px;
  list-style: none;
}

.footer-nav a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.95rem;
  transition: var(--transition-fast);
}

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

.footer-copy {
  color: var(--text-muted);
  font-size: 0.85rem;
}

/* Article Detail Styles */
.article-container {
  max-width: 860px;
  margin: 140px auto 80px;
  padding: 0 24px;
}

.article-header {
  margin-bottom: 40px;
  text-align: center;
}

.article-title-main {
  font-size: 2.5rem;
  font-weight: 800;
  line-height: 1.3;
  margin: 16px 0 24px;
}

.article-body {
  font-size: 1.05rem;
  line-height: 1.8;
  color: #cbd5e1;
}

.article-body h2 {
  font-size: 1.65rem;
  color: var(--text-primary);
  margin: 40px 0 16px;
  font-weight: 700;
}

.article-body h3 {
  font-size: 1.3rem;
  color: var(--text-primary);
  margin: 28px 0 12px;
  font-weight: 600;
}

.article-body p {
  margin-bottom: 20px;
}

.article-body ul, .article-body ol {
  margin: 0 0 24px 24px;
}

.article-body li {
  margin-bottom: 8px;
}

.article-body blockquote {
  border-left: 4px solid var(--accent-purple);
  padding: 16px 24px;
  background: rgba(139, 92, 246, 0.08);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: 28px 0;
  font-style: italic;
  color: #e2e8f0;
}

.article-body a {
  color: var(--accent-blue);
  text-decoration: underline;
  text-underline-offset: 4px;
}

.article-cta-box {
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.15) 0%, rgba(236, 72, 153, 0.15) 100%);
  padding: 36px;
  border-radius: var(--radius-lg);
  text-align: center;
  margin: 48px 0;
}

/* Responsive Media Queries */
@media (max-width: 992px) {
  .features-grid, .pricing-grid, .articles-grid, .reviews-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  .hero-title {
    font-size: 2.75rem;
  }
}

@media (max-width: 768px) {
  .nav-menu {
    display: none; /* Mobile menu auto collapse */
  }
  .hero {
    padding: 130px 0 60px;
  }
  .hero-title {
    font-size: 2rem;
  }
  .hero-subtitle {
    font-size: 1rem;
  }
  .hero-actions {
    flex-direction: column;
    width: 100%;
  }
  .hero-actions .btn {
    width: 100%;
  }
  .hero-stats {
    flex-wrap: wrap;
    gap: 24px;
  }
  .features-grid, .pricing-grid, .articles-grid, .reviews-grid {
    grid-template-columns: 1fr;
  }
  .pricing-grid {
    overflow-x: hidden;
  }
  .footer-nav {
    flex-direction: column;
    gap: 16px;
  }
}