/* ==========================================================================
   贝雪云机场 (Beixueyun) - Design System & Modern Stylesheet
   ========================================================================== */

:root {
  --bg-dark: #090d16;
  --bg-surface: #111827;
  --bg-surface-elevated: #1f293d;
  --bg-card: rgba(23, 32, 51, 0.7);
  --border-color: rgba(255, 255, 255, 0.08);
  --border-color-glow: rgba(59, 130, 246, 0.4);
  
  --primary: #3b82f6;
  --primary-hover: #2563eb;
  --primary-light: #60a5fa;
  --accent-cyan: #06b6d4;
  --accent-emerald: #10b981;
  --accent-purple: #8b5cf6;
  --accent-amber: #f59e0b;
  
  --text-main: #f3f4f6;
  --text-muted: #9ca3af;
  --text-dim: #6b7280;
  
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 25px rgba(59, 130, 246, 0.25);
  
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --radius-full: 9999px;
  
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
  background-color: var(--bg-dark);
  color: var(--text-main);
  line-height: 1.6;
}

body {
  min-height: 100vh;
  overflow-x: hidden;
  background: radial-gradient(circle at 50% 0%, rgba(59, 130, 246, 0.12) 0%, transparent 60%),
              radial-gradient(circle at 80% 40%, rgba(139, 92, 246, 0.08) 0%, transparent 50%),
              var(--bg-dark);
}

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

a:hover {
  color: #93c5fd;
}

.container {
  max-width: 1240px;
  margin: 0 auto;
  padding: 0 24px;
}

/* Header & Nav */
.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 100;
  backdrop-filter: blur(16px);
  background: rgba(9, 13, 22, 0.8);
  border-bottom: 1px solid var(--border-color);
  transition: var(--transition);
}

.header-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 20px;
  font-weight: 800;
  color: #fff;
  letter-spacing: -0.5px;
}

.logo-icon {
  width: 38px;
  height: 38px;
  background: linear-gradient(135deg, var(--accent-cyan), var(--primary), var(--accent-purple));
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-weight: 900;
  font-size: 20px;
  box-shadow: 0 0 15px rgba(6, 182, 212, 0.4);
}

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

.nav-links a {
  color: var(--text-muted);
  font-size: 15px;
  font-weight: 500;
}

.nav-links a:hover,
.nav-links a.active {
  color: #fff;
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 16px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 22px;
  border-radius: var(--radius-full);
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: var(--transition);
  text-decoration: none;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent-cyan), var(--primary));
  color: #fff;
  box-shadow: 0 4px 14px rgba(6, 182, 212, 0.35);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(6, 182, 212, 0.5);
  color: #fff;
}

.btn-secondary {
  background: rgba(255, 255, 255, 0.06);
  color: var(--text-main);
  border: 1px solid var(--border-color);
}

.btn-secondary:hover {
  background: rgba(255, 255, 255, 0.12);
  color: #fff;
}

.btn-accent {
  background: linear-gradient(135deg, var(--accent-emerald), #059669);
  color: #fff;
  box-shadow: 0 4px 14px rgba(16, 185, 129, 0.35);
}

.btn-accent:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(16, 185, 129, 0.5);
  color: #fff;
}

.mobile-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--text-main);
  font-size: 24px;
  cursor: pointer;
}

/* Hero Section */
.hero {
  padding: 140px 0 80px;
  text-align: center;
  position: relative;
}

.badge-pill {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 16px;
  border-radius: var(--radius-full);
  background: rgba(59, 130, 246, 0.1);
  border: 1px solid rgba(59, 130, 246, 0.3);
  color: var(--primary-light);
  font-size: 14px;
  font-weight: 500;
  margin-bottom: 24px;
}

.hero-title {
  font-size: 48px;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 20px;
  background: linear-gradient(135deg, #ffffff 30%, var(--text-muted) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: -1px;
}

.hero-title .gradient-text {
  background: linear-gradient(135deg, var(--accent-cyan), var(--primary-light), var(--accent-purple));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-subtitle {
  font-size: 18px;
  color: var(--text-muted);
  max-width: 760px;
  margin: 0 auto 36px;
}

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

.hero-features-bar {
  display: flex;
  justify-content: center;
  gap: 32px;
  flex-wrap: wrap;
  padding: 20px 32px;
  background: var(--bg-card);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  max-width: 960px;
  margin: 0 auto;
}

.hero-feature-item {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 14px;
  color: var(--text-main);
  font-weight: 500;
}

.hero-feature-icon {
  color: var(--accent-cyan);
  font-size: 18px;
}

/* Features Section */
.section {
  padding: 80px 0;
  position: relative;
}

.section-header {
  text-align: center;
  max-width: 720px;
  margin: 0 auto 50px;
}

.section-subtitle {
  color: var(--accent-cyan);
  font-size: 14px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 10px;
  display: block;
}

.section-title {
  font-size: 36px;
  font-weight: 800;
  color: #fff;
  margin-bottom: 16px;
  letter-spacing: -0.5px;
}

.section-desc {
  font-size: 16px;
  color: var(--text-muted);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 24px;
}

.feature-card {
  background: var(--bg-card);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 32px;
  transition: var(--transition);
}

.feature-card:hover {
  transform: translateY(-5px);
  border-color: var(--border-color-glow);
  box-shadow: var(--shadow-glow);
}

.feature-icon-wrapper {
  width: 54px;
  height: 54px;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, rgba(6, 182, 212, 0.15), rgba(59, 130, 246, 0.15));
  border: 1px solid rgba(6, 182, 212, 0.25);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;
  color: var(--accent-cyan);
  margin-bottom: 20px;
}

.feature-card h3 {
  font-size: 20px;
  font-weight: 700;
  color: #fff;
  margin-bottom: 12px;
}

.feature-card p {
  color: var(--text-muted);
  font-size: 15px;
}

/* Pricing Section */
.pricing-tabs {
  display: flex;
  justify-content: center;
  gap: 12px;
  margin-bottom: 40px;
  flex-wrap: wrap;
}

.tab-btn {
  padding: 10px 24px;
  border-radius: var(--radius-full);
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
}

.tab-btn:hover {
  color: #fff;
  background: rgba(255, 255, 255, 0.1);
}

.tab-btn.active {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
  box-shadow: 0 4px 14px rgba(59, 130, 246, 0.4);
}

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 28px;
}

.price-card {
  background: var(--bg-card);
  backdrop-filter: blur(14px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 32px 28px;
  display: flex;
  flex-direction: column;
  position: relative;
  transition: var(--transition);
  overflow: hidden;
}

.price-card.featured {
  border-color: rgba(6, 182, 212, 0.6);
  box-shadow: 0 8px 30px rgba(6, 182, 212, 0.2);
  background: linear-gradient(180deg, rgba(6, 182, 212, 0.08) 0%, var(--bg-card) 100%);
}

.price-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-lg);
}

.card-ribbon {
  position: absolute;
  top: 16px;
  right: -32px;
  transform: rotate(45deg);
  background: linear-gradient(135deg, var(--accent-cyan), var(--primary));
  color: #fff;
  font-size: 11px;
  font-weight: 700;
  padding: 4px 36px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
}

.plan-header {
  margin-bottom: 20px;
}

.plan-badge-group {
  display: flex;
  gap: 8px;
  margin-bottom: 12px;
  flex-wrap: wrap;
}

.plan-badge {
  display: inline-block;
  padding: 4px 10px;
  border-radius: var(--radius-sm);
  font-size: 12px;
  font-weight: 700;
}

.badge-cyan { background: rgba(6, 182, 212, 0.15); color: var(--accent-cyan); border: 1px solid rgba(6, 182, 212, 0.3); }
.badge-emerald { background: rgba(16, 185, 129, 0.15); color: var(--accent-emerald); border: 1px solid rgba(16, 185, 129, 0.3); }
.badge-purple { background: rgba(139, 92, 246, 0.15); color: var(--accent-purple); border: 1px solid rgba(139, 92, 246, 0.3); }

.plan-title {
  font-size: 24px;
  font-weight: 800;
  color: #fff;
  margin-bottom: 6px;
}

.plan-target {
  font-size: 13px;
  color: var(--text-muted);
  min-height: 40px;
}

.plan-price-box {
  margin: 20px 0;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--border-color);
}

.price-amount {
  font-size: 38px;
  font-weight: 900;
  color: #fff;
  letter-spacing: -1px;
}

.price-cycle {
  font-size: 14px;
  color: var(--text-muted);
  font-weight: 500;
}

.price-discount-note {
  font-size: 13px;
  color: var(--accent-emerald);
  margin-top: 4px;
  font-weight: 600;
}

.plan-features {
  list-style: none;
  margin-bottom: 30px;
  flex-grow: 1;
}

.plan-features li {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  font-size: 14px;
  color: var(--text-main);
  margin-bottom: 12px;
}

.plan-features li i {
  color: var(--accent-cyan);
  font-size: 16px;
  margin-top: 2px;
  flex-shrink: 0;
}

.plan-cta {
  width: 100%;
}

/* FAQ Accordion Section */
.faq-list {
  max-width: 860px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.faq-item {
  background: var(--bg-card);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: var(--transition);
}

.faq-item:hover {
  border-color: rgba(255, 255, 255, 0.15);
}

.faq-question {
  width: 100%;
  padding: 22px 28px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: none;
  border: none;
  color: #fff;
  font-size: 17px;
  font-weight: 700;
  text-align: left;
  cursor: pointer;
  gap: 16px;
}

.faq-icon {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.08);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  transition: var(--transition);
  flex-shrink: 0;
}

.faq-item.open .faq-icon {
  transform: rotate(180deg);
  background: var(--primary);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s ease, padding 0.35s ease;
  padding: 0 28px;
  color: var(--text-muted);
  font-size: 15px;
  line-height: 1.7;
}

.faq-item.open .faq-answer {
  max-height: 300px;
  padding: 0 28px 24px;
  border-top: 1px solid rgba(255, 255, 255, 0.04);
}

/* Articles / Knowledge Base Section */
.articles-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 28px;
}

.article-card {
  background: var(--bg-card);
  backdrop-filter: blur(12px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 28px;
  display: flex;
  flex-direction: column;
  transition: var(--transition);
}

.article-card:hover {
  transform: translateY(-5px);
  border-color: var(--border-color-glow);
  box-shadow: var(--shadow-glow);
}

.article-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 13px;
  color: var(--accent-cyan);
  margin-bottom: 12px;
  font-weight: 600;
}

.article-title {
  font-size: 19px;
  font-weight: 700;
  color: #fff;
  margin-bottom: 12px;
  line-height: 1.4;
}

.article-excerpt {
  color: var(--text-muted);
  font-size: 14px;
  line-height: 1.6;
  margin-bottom: 20px;
  flex-grow: 1;
}

.article-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-top: 1px solid var(--border-color);
  padding-top: 16px;
}

.article-link {
  font-size: 14px;
  font-weight: 700;
  color: var(--primary-light);
  display: flex;
  align-items: center;
  gap: 6px;
}

.article-link:hover {
  color: #fff;
  gap: 10px;
}

/* Article Page Layout (Article Detail) */
.article-page-header {
  padding: 130px 0 40px;
  border-bottom: 1px solid var(--border-color);
  background: radial-gradient(circle at 50% 0%, rgba(59, 130, 246, 0.15) 0%, transparent 70%);
}

.breadcrumbs {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 14px;
  color: var(--text-muted);
  margin-bottom: 20px;
}

.breadcrumbs a {
  color: var(--text-muted);
}

.breadcrumbs a:hover {
  color: #fff;
}

.article-header-title {
  font-size: 34px;
  font-weight: 800;
  color: #fff;
  line-height: 1.3;
  margin-bottom: 16px;
}

.article-header-meta {
  display: flex;
  align-items: center;
  gap: 20px;
  font-size: 14px;
  color: var(--text-muted);
  flex-wrap: wrap;
}

.article-body-container {
  padding: 60px 0 100px;
  max-width: 900px;
  margin: 0 auto;
}

.article-content {
  color: #d1d5db;
  font-size: 16px;
  line-height: 1.8;
}

.article-content h1,
.article-content h2,
.article-content h3,
.article-content h4 {
  color: #fff;
  font-weight: 800;
  margin: 36px 0 18px;
  line-height: 1.3;
}

.article-content h2 {
  font-size: 24px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border-color);
}

.article-content h3 {
  font-size: 20px;
  color: #e5e7eb;
}

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

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

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

.article-content table {
  width: 100%;
  border-collapse: collapse;
  margin: 24px 0;
  font-size: 14px;
  background: var(--bg-card);
  border-radius: var(--radius-sm);
  overflow: hidden;
}

.article-content th,
.article-content td {
  padding: 14px 18px;
  border: 1px solid var(--border-color);
  text-align: left;
}

.article-content th {
  background: rgba(255, 255, 255, 0.06);
  color: #fff;
  font-weight: 700;
}

.article-content blockquote {
  border-left: 4px solid var(--accent-cyan);
  background: rgba(6, 182, 212, 0.08);
  padding: 16px 20px;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: 24px 0;
  color: #e5e7eb;
}

/* Article CTA Box */
.article-cta-box {
  margin: 40px 0;
  padding: 32px;
  background: linear-gradient(135deg, rgba(6, 182, 212, 0.12), rgba(59, 130, 246, 0.15));
  border: 1px solid rgba(6, 182, 212, 0.4);
  border-radius: var(--radius-md);
  text-align: center;
  box-shadow: 0 8px 30px rgba(6, 182, 212, 0.15);
}

.article-cta-box h3 {
  font-size: 22px;
  color: #fff;
  margin-bottom: 10px;
  font-weight: 800;
}

.article-cta-box p {
  color: var(--text-muted);
  font-size: 15px;
  margin-bottom: 20px;
}

/* Footer */
.footer {
  background: #060911;
  border-top: 1px solid var(--border-color);
  padding: 60px 0 30px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr repeat(3, 1fr);
  gap: 40px;
  margin-bottom: 40px;
}

.footer-brand p {
  color: var(--text-muted);
  font-size: 14px;
  margin-top: 16px;
  max-width: 320px;
}

.footer-col h4 {
  color: #fff;
  font-size: 16px;
  font-weight: 700;
  margin-bottom: 20px;
}

.footer-col ul {
  list-style: none;
}

.footer-col li {
  margin-bottom: 12px;
}

.footer-col a {
  color: var(--text-muted);
  font-size: 14px;
}

.footer-col a:hover {
  color: #fff;
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.05);
  padding-top: 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 13px;
  color: var(--text-dim);
  flex-wrap: wrap;
  gap: 16px;
}

/* Media Queries */
@media (max-width: 992px) {
  .hero-title { font-size: 38px; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 768px) {
  .nav-links { display: none; }
  .mobile-toggle { display: block; }
  .nav-actions { display: none; }
  
  .nav-links.mobile-active {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 72px;
    left: 0;
    width: 100%;
    background: var(--bg-surface);
    padding: 24px;
    border-bottom: 1px solid var(--border-color);
  }

  .hero-title { font-size: 30px; }
  .hero-subtitle { font-size: 15px; }
  .pricing-grid { grid-template-columns: 1fr; }
  .articles-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
}