/* ==========================================================================
   XSUS 机场 (xsusvpn.cyou) - 官方落地页主样式表（高科技极速蓝主题）
   ========================================================================== */

:root {
  --bg-dark: #080d1a;
  --bg-card: #0f172a;
  --bg-card-hover: #1e293b;
  --border-color: rgba(255, 255, 255, 0.08);
  --border-glow: rgba(56, 189, 248, 0.35);

  --primary-sky: #38bdf8;
  --primary-blue: #0284c7;
  --primary-indigo: #6366f1;
  --accent-cyan: #06b6d4;
  --accent-green: #10b981;
  --accent-pink: #f43f5e;

  --text-main: #f8fafc;
  --text-muted: #cbd5e1;
  --text-sub: #94a3b8;

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Microsoft YaHei", sans-serif;
  --radius-lg: 16px;
  --radius-md: 12px;
  --radius-sm: 8px;
  --transition-fast: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Base Reset & Universal Styles */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  font-family: var(--font-sans);
  background-color: var(--bg-dark);
  color: var(--text-main);
  line-height: 1.6;
}

body {
  overflow-x: hidden;
  background: radial-gradient(circle at 50% 0%, rgba(14, 165, 233, 0.18) 0%, rgba(8, 13, 26, 1) 70%);
  min-height: 100vh;
}

a {
  color: var(--primary-sky);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: #7dd3fc;
}

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

.section-padding {
  padding: 80px 0;
}

.text-gradient {
  background: linear-gradient(135deg, #38bdf8, #818cf8, #c084fc);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.section-title {
  font-size: 2.25rem;
  font-weight: 800;
  text-align: center;
  margin-bottom: 12px;
  letter-spacing: -0.02em;
}

.section-desc {
  font-size: 1.1rem;
  color: var(--text-sub);
  text-align: center;
  max-width: 720px;
  margin: 0 auto 50px auto;
}

/* Button Styles */
.btn-primary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  background: linear-gradient(135deg, var(--primary-sky), var(--primary-indigo));
  color: #ffffff;
  font-weight: 600;
  font-size: 1rem;
  padding: 14px 28px;
  border-radius: 9999px;
  box-shadow: 0 4px 20px rgba(56, 189, 248, 0.35);
  transition: all var(--transition-fast);
  border: none;
  cursor: pointer;
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px rgba(99, 102, 241, 0.5);
  color: #ffffff;
}

.btn-secondary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  background: rgba(255, 255, 255, 0.05);
  color: var(--text-main);
  font-weight: 600;
  font-size: 1rem;
  padding: 14px 28px;
  border-radius: 9999px;
  border: 1px solid var(--border-color);
  transition: all var(--transition-fast);
  cursor: pointer;
}

.btn-secondary:hover {
  background: rgba(255, 255, 255, 0.1);
  border-color: rgba(255, 255, 255, 0.2);
  color: #ffffff;
}

/* Header & Navigation */
.header-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(8, 13, 26, 0.88);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  height: 72px;
  display: flex;
  align-items: center;
}

.nav-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
}

.logo-link {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--text-main);
  font-weight: 800;
  font-size: 1.3rem;
  letter-spacing: -0.01em;
}

.logo-img {
  width: 38px;
  height: 38px;
}

.logo-badge {
  background: rgba(56, 189, 248, 0.15);
  color: var(--primary-sky);
  border: 1px solid rgba(56, 189, 248, 0.3);
  font-size: 0.72rem;
  font-weight: 700;
  padding: 2px 8px;
  border-radius: 99px;
  text-transform: uppercase;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 28px;
  list-style: none;
}

.nav-links a {
  color: var(--text-muted);
  font-size: 0.95rem;
  font-weight: 500;
}

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

.mobile-menu-toggle {
  display: none;
  background: transparent;
  border: none;
  color: var(--text-main);
  font-size: 1.6rem;
  cursor: pointer;
  padding: 4px;
}

/* Mobile Drawer Menu */
.mobile-nav-drawer {
  position: fixed;
  top: 72px;
  left: 0;
  width: 100%;
  background: rgba(15, 23, 42, 0.98);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-color);
  padding: 24px;
  display: none;
  flex-direction: column;
  gap: 16px;
  z-index: 99;
  transform: translateY(-10px);
  opacity: 0;
  transition: all 0.3s ease;
}

.mobile-nav-drawer.active {
  display: flex;
  transform: translateY(0);
  opacity: 1;
}

.mobile-nav-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.mobile-nav-links a {
  color: var(--text-main);
  font-size: 1.1rem;
  font-weight: 600;
  display: block;
}

/* Hero Section */
.hero-section {
  padding: 100px 0 70px 0;
  text-align: center;
  position: relative;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: rgba(56, 189, 248, 0.1);
  border: 1px solid rgba(56, 189, 248, 0.3);
  color: var(--primary-sky);
  padding: 6px 16px;
  border-radius: 99px;
  font-size: 0.9rem;
  font-weight: 600;
  margin-bottom: 24px;
}

.hero-badge span.pulse-dot {
  width: 8px;
  height: 8px;
  background-color: var(--accent-green);
  border-radius: 50%;
  box-shadow: 0 0 10px var(--accent-green);
  animation: pulse 2s infinite;
}

@keyframes pulse {
  0% { transform: scale(0.95); box-shadow: 0 0 0 0 rgba(16, 185, 129, 0.7); }
  70% { transform: scale(1); box-shadow: 0 0 0 8px rgba(16, 185, 129, 0); }
  100% { transform: scale(0.95); box-shadow: 0 0 0 0 rgba(16, 185, 129, 0); }
}

.hero-title {
  font-size: 3.4rem;
  font-weight: 900;
  line-height: 1.2;
  margin-bottom: 20px;
  letter-spacing: -0.03em;
}

.hero-subtitle {
  font-size: 1.2rem;
  color: var(--text-muted);
  max-width: 780px;
  margin: 0 auto 36px auto;
  line-height: 1.8;
}

.hero-actions {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  flex-wrap: wrap;
  margin-bottom: 40px;
}

.hero-stats-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  max-width: 900px;
  margin: 50px auto 0 auto;
  background: rgba(15, 23, 42, 0.6);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 24px;
}

.stat-item h3 {
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--primary-sky);
  margin-bottom: 4px;
}

.stat-item p {
  font-size: 0.88rem;
  color: var(--text-sub);
}

/* Node Monitor / Speed Test Section */
.monitor-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  margin-top: 30px;
}

.node-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  transition: all var(--transition-fast);
}

.node-card:hover {
  border-color: var(--border-glow);
  transform: translateY(-3px);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.4);
}

.node-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.node-flag-title {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1.05rem;
}

.node-tag {
  font-size: 0.75rem;
  background: rgba(56, 189, 248, 0.15);
  color: var(--primary-sky);
  padding: 2px 8px;
  border-radius: 4px;
  font-weight: 600;
}

.node-metrics {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: rgba(0, 0, 0, 0.3);
  padding: 10px 14px;
  border-radius: var(--radius-sm);
}

.metric-label {
  font-size: 0.8rem;
  color: var(--text-sub);
}

.metric-val {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--accent-green);
}

/* Feature Cards Grid */
.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 32px 24px;
  transition: all var(--transition-fast);
}

.feature-card:hover {
  border-color: var(--border-glow);
  background: var(--bg-card-hover);
  transform: translateY(-4px);
}

.feature-icon {
  width: 56px;
  height: 56px;
  background: rgba(56, 189, 248, 0.1);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.8rem;
  margin-bottom: 20px;
}

.feature-card h3 {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text-main);
}

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

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

.price-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 36px 24px;
  display: flex;
  flex-direction: column;
  position: relative;
  transition: all var(--transition-fast);
}

.price-card.popular {
  border: 2px solid var(--primary-sky);
  box-shadow: 0 0 30px rgba(56, 189, 248, 0.25);
  background: linear-gradient(180deg, rgba(14, 165, 233, 0.12) 0%, var(--bg-card) 100%);
  transform: scale(1.03);
}

.popular-badge {
  position: absolute;
  top: -14px;
  left: 50%;
  transform: translateX(-50%);
  background: linear-gradient(135deg, var(--primary-sky), var(--primary-indigo));
  color: #ffffff;
  font-size: 0.8rem;
  font-weight: 700;
  padding: 4px 14px;
  border-radius: 99px;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.price-card h3 {
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.price-amount {
  font-size: 2.5rem;
  font-weight: 900;
  color: var(--text-main);
  margin-bottom: 6px;
}

.price-amount span {
  font-size: 1rem;
  font-weight: 500;
  color: var(--text-sub);
}

.price-desc {
  font-size: 0.88rem;
  color: var(--text-sub);
  margin-bottom: 24px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--border-color);
}

.price-features {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 32px;
  flex-grow: 1;
}

.price-features li {
  font-size: 0.92rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 8px;
}

.price-features li span.check {
  color: var(--accent-green);
  font-weight: bold;
}

/* User Reviews / Testimonials */
.testimonials-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.review-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 28px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.review-stars {
  color: #f59e0b;
  font-size: 1.1rem;
  margin-bottom: 12px;
}

.review-text {
  font-size: 0.95rem;
  color: var(--text-muted);
  line-height: 1.7;
  margin-bottom: 20px;
  font-style: italic;
}

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

.user-avatar {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--primary-sky), var(--primary-indigo));
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  color: #fff;
  font-size: 1rem;
}

.user-info h4 {
  font-size: 0.98rem;
  font-weight: 700;
  color: var(--text-main);
}

.user-info p {
  font-size: 0.8rem;
  color: var(--text-sub);
}

/* FAQ Accordion Section */
.faq-container {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

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

.faq-item.active {
  border-color: var(--border-glow);
}

.faq-question {
  padding: 20px 24px;
  font-size: 1.05rem;
  font-weight: 700;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  user-select: none;
}

.faq-toggle-icon {
  font-size: 1.3rem;
  transition: transform 0.3s ease;
  color: var(--primary-sky);
}

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

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s cubic-bezier(0, 1, 0, 1), padding 0.35s ease;
  padding: 0 24px;
  font-size: 0.95rem;
  color: var(--text-muted);
  line-height: 1.8;
}

.faq-item.active .faq-answer {
  max-height: 500px;
  padding: 0 24px 20px 24px;
  transition: max-height 0.35s cubic-bezier(1, 0, 1, 0), padding 0.35s ease;
}

/* Articles Columns & Article Grid */
.articles-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.article-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: all var(--transition-fast);
}

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

.article-body {
  padding: 24px;
  display: flex;
  flex-direction: column;
  flex-grow: 1;
}

.article-category {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--primary-sky);
  text-transform: uppercase;
  margin-bottom: 10px;
  letter-spacing: 0.05em;
}

.article-title {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 12px;
  line-height: 1.4;
  color: var(--text-main);
}

.article-excerpt {
  font-size: 0.9rem;
  color: var(--text-sub);
  line-height: 1.6;
  margin-bottom: 20px;
  flex-grow: 1;
}

.article-link {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--primary-sky);
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

/* Article Detail Page Layout */
.article-detail-container {
  max-width: 860px;
  margin: 40px auto 80px auto;
  padding: 0 20px;
}

.breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.88rem;
  color: var(--text-sub);
  margin-bottom: 28px;
}

.article-header-meta {
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--border-color);
}

.article-main-title {
  font-size: 2.4rem;
  font-weight: 900;
  line-height: 1.3;
  margin-bottom: 16px;
  letter-spacing: -0.02em;
}

.article-meta-info {
  display: flex;
  align-items: center;
  gap: 20px;
  font-size: 0.88rem;
  color: var(--text-sub);
}

.article-content {
  font-size: 1.05rem;
  line-height: 1.85;
  color: var(--text-muted);
}

.article-content h2 {
  font-size: 1.6rem;
  font-weight: 800;
  color: var(--text-main);
  margin: 36px 0 16px 0;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
}

.article-content h3 {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--primary-sky);
  margin: 28px 0 14px 0;
}

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

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

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

.cta-box-inline {
  background: linear-gradient(135deg, rgba(14, 165, 233, 0.15) 0%, rgba(99, 102, 241, 0.15) 100%);
  border: 1px solid var(--border-glow);
  border-radius: var(--radius-lg);
  padding: 30px;
  text-align: center;
  margin: 40px 0;
}

.cta-box-inline h3 {
  font-size: 1.4rem;
  color: var(--text-main);
  margin-bottom: 10px;
}

.cta-box-inline p {
  font-size: 0.95rem;
  color: var(--text-muted);
  margin-bottom: 20px;
}

/* Footer Section & Core Task 2 PBN Friend Links */
footer {
  background: #040711;
  border-top: 1px solid var(--border-color);
  padding: 60px 0 30px 0;
}

.footer-top {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 40px;
  padding-bottom: 40px;
  border-bottom: 1px solid var(--border-color);
}

.footer-brand p {
  font-size: 0.9rem;
  color: var(--text-sub);
  margin-top: 14px;
  line-height: 1.7;
}

.footer-col h5 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 16px;
}

.footer-col ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.footer-col ul a {
  color: var(--text-sub);
  font-size: 0.9rem;
}

.footer-col ul a:hover {
  color: var(--primary-sky);
}

.footer-bottom {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 14px;
  text-align: center;
  font-size: 0.85rem;
  color: var(--text-sub);
}

/* Core Task 2: Low-profile PBN Link Area */
.footer-friend-links {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  font-size: 0.82rem;
  color: #64748b;
  margin-top: 6px;
}

.footer-friend-links span.label {
  color: #64748b;
}

.footer-friend-links a {
  color: #94a3b8;
  text-decoration: none;
  transition: color var(--transition-fast);
}

.footer-friend-links a:hover {
  color: var(--primary-sky);
  text-decoration: underline;
}

/* Mobile Responsiveness Rules */
@media (max-width: 1024px) {
  .pricing-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  .price-card.popular {
    transform: none;
  }
  .features-grid, .testimonials-grid, .articles-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  .footer-top {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 768px) {
  .nav-links, .nav-cta-btn {
    display: none;
  }
  .mobile-menu-toggle {
    display: block;
  }
  .hero-title {
    font-size: 2.3rem;
  }
  .hero-stats-row {
    grid-template-columns: repeat(2, 1fr);
  }
  .monitor-grid {
    grid-template-columns: 1fr;
  }
  .features-grid, .testimonials-grid, .articles-grid {
    grid-template-columns: 1fr;
  }
  .pricing-grid {
    grid-template-columns: 1fr;
  }
  .footer-top {
    grid-template-columns: 1fr;
    gap: 30px;
  }
}