/* ==========================================================================
   老头VPN (laotouvpn.cfd) - VLBI Aperture Synthesis (甚长基线干涉与深空射电风)
   Design Tokens & Modern CSS Architecture
   ========================================================================== */

:root {
  /* VLBI Color System */
  --bg-deep-space: #06080D;
  --bg-card: rgba(14, 18, 27, 0.75);
  --bg-card-hover: rgba(22, 28, 42, 0.85);
  --bg-elevated: #111622;
  
  --accent-gold: #FCD34D;        /* 射电干涉冷光金 */
  --accent-gold-glow: rgba(252, 211, 77, 0.35);
  --accent-gold-soft: rgba(252, 211, 77, 0.12);
  
  --cyan-telemetry: #38BDF8;      /* 测站冷蓝 */
  --emerald-signal: #34D399;      /* 信号同步绿 */
  --purple-fringe: #A78BFA;       /* 干涉频谱紫 */
  
  --text-main: #F1F5F9;
  --text-muted: #94A3B8;
  --text-dim: #64748B;
  
  --border-dim: rgba(252, 211, 77, 0.15);
  --border-bright: rgba(252, 211, 77, 0.45);
  --border-cyan: rgba(56, 189, 248, 0.25);
  
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Roboto Mono', Consolas, monospace;
  --font-sans: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;
  
  --shadow-gold: 0 0 25px rgba(252, 211, 77, 0.2);
  --shadow-card: 0 10px 30px -10px rgba(0, 0, 0, 0.7);
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
  background-color: var(--bg-deep-space);
  color: var(--text-main);
  font-family: var(--font-sans);
  overflow-x: hidden;
}

body {
  min-height: 100vh;
  line-height: 1.6;
  background-color: var(--bg-deep-space);
  position: relative;
}

/* Cosmic Parabolic Mesh Background Overlay */
body::before {
  content: "";
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background-image: 
    radial-gradient(circle at 50% 20%, rgba(56, 189, 248, 0.05) 0%, transparent 60%),
    radial-gradient(circle at 80% 80%, rgba(252, 211, 77, 0.04) 0%, transparent 50%),
    linear-gradient(to right, rgba(252, 211, 77, 0.03) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(252, 211, 77, 0.03) 1px, transparent 1px);
  background-size: 100% 100%, 100% 100%, 40px 40px, 40px 40px;
  pointer-events: none;
  z-index: -2;
}

/* Canvas Starfield / Interference Lines */
#vlbi-canvas {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: -1;
  opacity: 0.85;
}

/* Custom Cursor Trail Effect Container */
.custom-cursor-dot {
  position: fixed;
  top: 0;
  left: 0;
  width: 8px;
  height: 8px;
  background: var(--accent-gold);
  border-radius: 50%;
  pointer-events: none;
  z-index: 9999;
  transform: translate(-50%, -50%);
  box-shadow: 0 0 10px var(--accent-gold), 0 0 20px var(--accent-gold);
  transition: transform 0.05s ease;
}

.custom-cursor-ring {
  position: fixed;
  top: 0;
  left: 0;
  width: 36px;
  height: 36px;
  border: 1px dashed var(--accent-gold);
  border-radius: 50%;
  pointer-events: none;
  z-index: 9998;
  transform: translate(-50%, -50%);
  opacity: 0.6;
  transition: transform 0.15s ease-out, opacity 0.2s ease, width 0.2s ease, height 0.2s ease;
  animation: vlbi-rotate 20s linear infinite;
}

@keyframes vlbi-rotate {
  from { transform: translate(-50%, -50%) rotate(0deg); }
  to { transform: translate(-50%, -50%) rotate(360deg); }
}

/* Core Layout Container */
.container {
  max-width: 1240px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* Typography & Visual Accents */
h1, h2, h3, h4 {
  font-family: var(--font-sans);
  font-weight: 700;
  color: var(--text-main);
  letter-spacing: -0.02em;
}

.telemetry-tag {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--accent-gold);
  background: var(--accent-gold-soft);
  border: 1px solid var(--border-dim);
  padding: 0.35rem 0.85rem;
  border-radius: 20px;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  box-shadow: 0 0 15px rgba(252, 211, 77, 0.1);
}

.telemetry-tag::before {
  content: "";
  display: inline-block;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background-color: var(--emerald-signal);
  box-shadow: 0 0 8px var(--emerald-signal);
  animation: pulse-signal 1.8s infinite;
}

@keyframes pulse-signal {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.4; transform: scale(1.3); }
}

.highlight-gold {
  color: var(--accent-gold);
  text-shadow: 0 0 12px rgba(252, 211, 77, 0.4);
}

/* Top Navigation Bar */
.navbar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(6, 8, 13, 0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-dim);
}

.nav-container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 76px;
}

.logo-brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  color: var(--text-main);
  font-weight: 800;
  font-size: 1.35rem;
}

.logo-icon {
  width: 38px;
  height: 38px;
  background: linear-gradient(135deg, rgba(252, 211, 77, 0.2), rgba(56, 189, 248, 0.1));
  border: 1px solid var(--accent-gold);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--accent-gold);
  box-shadow: 0 0 12px var(--accent-gold-glow);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 2rem;
  list-style: none;
}

.nav-link {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 500;
  transition: color 0.25s ease;
}

.nav-link:hover {
  color: var(--accent-gold);
}

.btn-cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.6rem;
  background: linear-gradient(135deg, var(--accent-gold) 0%, #F59E0B 100%);
  color: #06080D;
  font-weight: 700;
  font-size: 0.95rem;
  padding: 0.75rem 1.6rem;
  border-radius: var(--radius-md);
  text-decoration: none;
  transition: all 0.3s ease;
  box-shadow: 0 0 20px var(--accent-gold-glow);
  border: none;
  cursor: pointer;
}

.btn-cta:hover {
  transform: translateY(-2px);
  box-shadow: 0 0 30px rgba(252, 211, 77, 0.6);
  background: linear-gradient(135deg, #FDE68A 0%, var(--accent-gold) 100%);
}

.btn-secondary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.6rem;
  background: rgba(255, 255, 255, 0.04);
  color: var(--text-main);
  font-weight: 600;
  font-size: 0.95rem;
  padding: 0.75rem 1.6rem;
  border-radius: var(--radius-md);
  text-decoration: none;
  border: 1px solid var(--border-bright);
  transition: all 0.3s ease;
}

.btn-secondary:hover {
  background: rgba(252, 211, 77, 0.1);
  border-color: var(--accent-gold);
  color: var(--accent-gold);
}

/* Mobile Menu Toggle */
.mobile-menu-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--text-main);
  font-size: 1.5rem;
  cursor: pointer;
}

/* Hero Section */
.hero {
  padding: 5rem 0 4rem 0;
  position: relative;
  text-align: center;
}

.hero-header-badge {
  margin-bottom: 1.5rem;
}

.hero-title {
  font-size: clamp(2.2rem, 5vw, 3.8rem);
  line-height: 1.15;
  margin-bottom: 1.5rem;
  max-width: 960px;
  margin-left: auto;
  margin-right: auto;
}

.hero-subtitle {
  font-size: 1.15rem;
  color: var(--text-muted);
  max-width: 780px;
  margin: 0 auto 2.5rem auto;
  line-height: 1.7;
}

.hero-actions {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1.25rem;
  margin-bottom: 3.5rem;
  flex-wrap: wrap;
}

/* Telemetry Monitoring Console Dashboard */
.telemetry-dashboard {
  background: var(--bg-card);
  border: 1px solid var(--border-bright);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  box-shadow: var(--shadow-card), 0 0 30px rgba(0, 0, 0, 0.5);
  position: relative;
  backdrop-filter: blur(12px);
  margin-top: 1rem;
}

.telemetry-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  padding-bottom: 1rem;
  margin-bottom: 1.5rem;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--text-muted);
}

.telemetry-metrics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.25rem;
}

.metric-card {
  background: rgba(6, 8, 13, 0.6);
  border: 1px solid var(--border-dim);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  text-align: left;
  position: relative;
  overflow: hidden;
}

.metric-card::after {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  width: 4px;
  height: 100%;
  background: var(--accent-gold);
  opacity: 0.5;
}

.metric-label {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--text-dim);
  text-transform: uppercase;
  margin-bottom: 0.4rem;
}

.metric-value {
  font-family: var(--font-mono);
  font-size: 1.8rem;
  font-weight: 700;
  color: var(--accent-gold);
}

.metric-sub {
  font-size: 0.8rem;
  color: var(--emerald-signal);
  margin-top: 0.3rem;
  display: flex;
  align-items: center;
  gap: 0.3rem;
}

/* Radio Spectrum Waves Banner */
.fringe-spectrum-bar {
  height: 60px;
  width: 100%;
  background: linear-gradient(90deg, 
    rgba(6, 8, 13, 1) 0%, 
    rgba(252, 211, 77, 0.08) 25%, 
    rgba(56, 189, 248, 0.12) 50%, 
    rgba(167, 139, 250, 0.08) 75%, 
    rgba(6, 8, 13, 1) 100%);
  margin: 3rem 0;
  border-top: 1px solid var(--border-dim);
  border-bottom: 1px solid var(--border-dim);
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

/* Grid Parabolic Card Styles */
.section-title-wrapper {
  text-align: center;
  margin-bottom: 3.5rem;
}

.section-title {
  font-size: 2.2rem;
  margin-bottom: 0.75rem;
}

.section-subtitle {
  color: var(--text-muted);
  font-size: 1.05rem;
  max-width: 680px;
  margin: 0 auto;
}

.grid-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 2rem;
}

.vlbi-card {
  background: var(--bg-card);
  border: 1px solid var(--border-dim);
  border-radius: var(--radius-lg);
  padding: 2rem;
  position: relative;
  overflow: hidden;
  transition: all 0.35s ease;
  backdrop-filter: blur(8px);
}

/* Antenna Grid Mesh Effect on Card Hover */
.vlbi-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-image: 
    radial-gradient(circle at 100% 0%, rgba(252, 211, 77, 0.08) 0%, transparent 50%),
    repeating-linear-gradient(0deg, transparent, transparent 19px, rgba(252, 211, 77, 0.04) 20px),
    repeating-linear-gradient(90deg, transparent, transparent 19px, rgba(252, 211, 77, 0.04) 20px);
  pointer-events: none;
  opacity: 0.5;
  transition: opacity 0.3s ease;
}

.vlbi-card:hover {
  transform: translateY(-5px);
  border-color: var(--border-bright);
  box-shadow: var(--shadow-gold), var(--shadow-card);
}

.vlbi-card:hover::before {
  opacity: 0.9;
}

.card-icon {
  width: 52px;
  height: 52px;
  background: rgba(252, 211, 77, 0.1);
  border: 1px solid var(--accent-gold);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--accent-gold);
  font-size: 1.5rem;
  margin-bottom: 1.25rem;
}

.card-title {
  font-size: 1.3rem;
  margin-bottom: 0.75rem;
}

.card-desc {
  color: var(--text-muted);
  font-size: 0.95rem;
  line-height: 1.65;
}

/* Pricing Tier Cards Section */
.pricing-section {
  padding: 5rem 0;
  position: relative;
}

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
  align-items: stretch;
}

.pricing-card {
  background: var(--bg-card);
  border: 1px solid var(--border-dim);
  border-radius: var(--radius-lg);
  padding: 2.25rem;
  display: flex;
  flex-direction: column;
  position: relative;
  transition: all 0.35s ease;
}

.pricing-card.featured {
  border-color: var(--accent-gold);
  background: linear-gradient(180deg, rgba(22, 28, 42, 0.95) 0%, rgba(14, 18, 27, 0.85) 100%);
  box-shadow: 0 0 35px rgba(252, 211, 77, 0.15);
  transform: scale(1.03);
}

.pricing-badge {
  position: absolute;
  top: -14px;
  right: 24px;
  background: var(--accent-gold);
  color: #06080D;
  font-weight: 800;
  font-size: 0.75rem;
  font-family: var(--font-mono);
  padding: 0.3rem 0.8rem;
  border-radius: 12px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.pricing-header {
  margin-bottom: 1.5rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  padding-bottom: 1.5rem;
}

.pricing-name {
  font-size: 1.35rem;
  margin-bottom: 0.5rem;
}

.pricing-price {
  font-family: var(--font-mono);
  font-size: 2.8rem;
  font-weight: 800;
  color: var(--accent-gold);
  display: flex;
  align-items: baseline;
  gap: 0.3rem;
}

.pricing-currency {
  font-size: 1.4rem;
}

.pricing-period {
  font-size: 0.9rem;
  color: var(--text-dim);
  font-weight: 400;
}

.pricing-features {
  list-style: none;
  margin-bottom: 2rem;
  flex-grow: 1;
}

.pricing-features li {
  padding: 0.6rem 0;
  color: var(--text-muted);
  font-size: 0.92rem;
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

.pricing-features li::before {
  content: "✓";
  color: var(--accent-gold);
  font-weight: bold;
}

/* Articles Hub Section */
.articles-section {
  padding: 5rem 0;
}

.article-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 2rem;
}

.article-card {
  background: var(--bg-card);
  border: 1px solid var(--border-dim);
  border-radius: var(--radius-md);
  padding: 1.75rem;
  display: flex;
  flex-direction: column;
  transition: all 0.3s ease;
}

.article-card:hover {
  border-color: var(--accent-gold);
  transform: translateY(-4px);
}

.article-meta {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--cyan-telemetry);
  margin-bottom: 0.75rem;
  display: flex;
  gap: 1rem;
}

.article-title {
  font-size: 1.15rem;
  line-height: 1.45;
  margin-bottom: 0.75rem;
}

.article-title a {
  color: var(--text-main);
  text-decoration: none;
  transition: color 0.2s ease;
}

.article-title a:hover {
  color: var(--accent-gold);
}

.article-excerpt {
  font-size: 0.9rem;
  color: var(--text-muted);
  line-height: 1.6;
  margin-bottom: 1.25rem;
  flex-grow: 1;
}

.article-link {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--accent-gold);
  text-decoration: none;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
}

.article-link:hover {
  text-decoration: underline;
}

/* User Feedback Testimonials */
.testimonials-section {
  padding: 5rem 0;
}

.testimonials-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}

.testimonial-card {
  background: var(--bg-card);
  border: 1px solid var(--border-dim);
  border-radius: var(--radius-md);
  padding: 1.5rem;
}

.testimonial-user {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  margin-bottom: 1rem;
}

.user-avatar {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent-gold), var(--cyan-telemetry));
  display: flex;
  align-items: center;
  justify-content: center;
  color: #06080D;
  font-weight: bold;
}

.user-info h4 {
  font-size: 0.95rem;
}

.user-info span {
  font-size: 0.78rem;
  color: var(--text-dim);
}

.rating-stars {
  color: var(--accent-gold);
  margin-bottom: 0.75rem;
  font-size: 0.9rem;
}

.testimonial-text {
  font-size: 0.9rem;
  color: var(--text-muted);
  line-height: 1.6;
}

/* FAQ Accordion Section */
.faq-section {
  padding: 5rem 0;
}

.faq-list {
  max-width: 860px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.faq-item {
  background: var(--bg-card);
  border: 1px solid var(--border-dim);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: border-color 0.3s ease;
}

.faq-question {
  width: 100%;
  padding: 1.25rem 1.5rem;
  background: none;
  border: none;
  color: var(--text-main);
  font-size: 1.05rem;
  font-weight: 600;
  text-align: left;
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
}

.faq-icon {
  color: var(--accent-gold);
  font-size: 1.2rem;
  transition: transform 0.3s ease;
}

.faq-item.active .faq-icon {
  transform: rotate(45deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s ease, padding 0.35s ease;
  padding: 0 1.5rem;
  color: var(--text-muted);
  font-size: 0.95rem;
  line-height: 1.65;
}

.faq-item.active .faq-answer {
  max-height: 300px;
  padding: 0 1.5rem 1.25rem 1.5rem;
}

/* Article Content Layout Page Styling */
.article-page-body {
  padding: 3rem 0 5rem 0;
}

.article-container {
  max-width: 860px;
  margin: 0 auto;
  background: var(--bg-card);
  border: 1px solid var(--border-dim);
  border-radius: var(--radius-lg);
  padding: 3rem 2.5rem;
  backdrop-filter: blur(12px);
}

.article-header {
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
  padding-bottom: 2rem;
  margin-bottom: 2.5rem;
}

.article-title-main {
  font-size: 2.1rem;
  line-height: 1.3;
  margin-bottom: 1rem;
}

.article-content {
  color: #CBD5E1;
  font-size: 1.02rem;
  line-height: 1.8;
}

.article-content h2 {
  font-size: 1.5rem;
  margin: 2.2rem 0 1rem 0;
  color: var(--accent-gold);
  border-left: 3px solid var(--accent-gold);
  padding-left: 0.75rem;
}

.article-content h3 {
  font-size: 1.2rem;
  margin: 1.6rem 0 0.8rem 0;
  color: var(--cyan-telemetry);
}

.article-content p {
  margin-bottom: 1.25rem;
}

.article-content ul, .article-content ol {
  margin-left: 1.5rem;
  margin-bottom: 1.5rem;
}

.article-content li {
  margin-bottom: 0.5rem;
}

.article-cta-box {
  background: linear-gradient(135deg, rgba(252, 211, 77, 0.1), rgba(56, 189, 248, 0.05));
  border: 1px solid var(--border-bright);
  border-radius: var(--radius-md);
  padding: 2rem;
  text-align: center;
  margin: 3rem 0;
}

/* Footer & PBN Link Matrix Section */
footer.site-footer {
  background: #040508;
  border-top: 1px solid var(--border-dim);
  padding: 3.5rem 0 2rem 0;
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-dim);
  position: relative;
}

.footer-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2rem;
}

.footer-logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  color: var(--text-main);
  font-weight: 700;
  font-size: 1.1rem;
}

.footer-nav {
  display: flex;
  gap: 1.5rem;
  flex-wrap: wrap;
  justify-content: center;
}

.footer-nav a {
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.2s ease;
}

.footer-nav a:hover {
  color: var(--accent-gold);
}

/* Low-profile Subtle PBN Friendly Links Matrix */
.pbn-link-matrix {
  margin-top: 1.5rem;
  padding-top: 1.5rem;
  border-top: 1px dashed rgba(255, 255, 255, 0.06);
  max-width: 900px;
  width: 100%;
}

.pbn-title {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  text-transform: uppercase;
  color: var(--text-dim);
  letter-spacing: 0.1em;
  margin-bottom: 0.75rem;
  opacity: 0.6;
}

.pbn-links-container {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.75rem 1.25rem;
}

.pbn-link {
  color: var(--text-dim);
  font-size: 0.75rem;
  text-decoration: none;
  opacity: 0.55;
  transition: all 0.25s ease;
}

.pbn-link:hover {
  color: var(--accent-gold);
  opacity: 1;
}

.copyright {
  font-size: 0.78rem;
  color: var(--text-dim);
  margin-top: 1rem;
}

/* Responsive Media Queries */
@media (max-width: 768px) {
  .nav-links {
    display: none;
    position: absolute;
    top: 76px;
    left: 0;
    width: 100%;
    background: #06080D;
    flex-direction: column;
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-dim);
  }

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

  .mobile-menu-toggle {
    display: block;
  }

  .hero-title {
    font-size: 2rem;
  }

  .article-container {
    padding: 1.75rem 1.25rem;
  }

  .pricing-card.featured {
    transform: none;
  }

  .custom-cursor-dot, .custom-cursor-ring {
    display: none;
  }
}