/* ==============================================================================
   NordVPN 官方设计系统 - 生产级现代化网络安全风格 (nord.css)
   主色调: 深度极光蓝 (#4687FF) · 星际深蓝底色 (#0B132B / #0E1726) · 荧光青 (#00D2D3)
   ============================================================================== */

:root {
  --nord-navy-deep: #080E1C;
  --nord-navy-base: #0B132B;
  --nord-navy-surface: #121E3B;
  --nord-navy-card: #18284C;
  --nord-navy-hover: #1F3360;
  
  --nord-blue: #4687FF;
  --nord-blue-dark: #1E60E0;
  --nord-blue-hover: #3377F5;
  --nord-blue-glow: rgba(70, 135, 255, 0.28);
  --nord-blue-subtle: rgba(70, 135, 255, 0.1);
  
  --nord-cyan: #00D2D3;
  --nord-cyan-glow: rgba(0, 210, 211, 0.2);
  --nord-green: #10B981;
  --nord-red: #EF4444;
  --nord-yellow: #F59E0B;
  
  --nord-border: rgba(255, 255, 255, 0.1);
  --nord-border-focus: rgba(70, 135, 255, 0.5);
  
  --text-white: #FFFFFF;
  --text-secondary: #C8D6E5;
  --text-muted: #8395A7;
  
  --font-main: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 22px;
  --radius-full: 9999px;
  
  --shadow-sm: 0 2px 6px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 6px 16px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 12px 32px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 24px var(--nord-blue-glow);
  
  --transition-fast: 0.18s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 0.28s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  font-family: var(--font-main);
  background-color: var(--nord-navy-base);
  color: var(--text-secondary);
  scroll-behavior: smooth;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
}

img, svg {
  vertical-align: middle;
}

a {
  color: var(--nord-blue);
  text-decoration: none;
  transition: color var(--transition-fast);
}
a:hover {
  color: var(--nord-cyan);
}

code, pre {
  font-family: var(--font-mono);
}

.container {
  width: 100%;
  max-width: 1200px;
  margin-left: auto;
  margin-right: auto;
  padding-left: 24px;
  padding-right: 24px;
}

.container-nav {
  width: 100%;
  max-width: 1360px;
  margin-left: auto;
  margin-right: auto;
  padding-left: 24px;
  padding-right: 24px;
}

/* ==============================================================================
   Top Notice & Announcement
   ============================================================================== */
.top-notice {
  background: linear-gradient(90deg, #091224, #122146, #091224);
  border-bottom: 1px solid rgba(70, 135, 255, 0.25);
  padding: 8px 16px;
  font-size: 0.85rem;
  text-align: center;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  flex-wrap: wrap;
}
.top-notice strong {
  color: var(--text-white);
}
.top-notice a {
  color: var(--nord-cyan);
  font-weight: 600;
  text-decoration: underline;
  text-underline-offset: 3px;
}
.top-notice a:hover {
  color: #FFFFFF;
}

/* ==============================================================================
   Header Navigation
   ============================================================================== */
.nord-header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: rgba(11, 19, 43, 0.92);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--nord-border);
  transition: background var(--transition-normal);
}

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

.nav-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
}
.nav-brand:hover {
  opacity: 0.95;
}

.brand-badge {
  background: var(--nord-blue-subtle);
  color: var(--nord-blue);
  border: 1px solid rgba(70, 135, 255, 0.3);
  font-size: 0.75rem;
  font-weight: 700;
  padding: 3px 8px;
  border-radius: var(--radius-sm);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

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

.nav-link {
  color: var(--text-secondary);
  font-size: 0.95rem;
  font-weight: 500;
  padding: 8px 0;
  position: relative;
  transition: color var(--transition-fast);
}
.nav-link:hover, .nav-link.active {
  color: var(--text-white);
}
.nav-link.active::after {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--nord-blue);
  border-radius: 2px;
  box-shadow: 0 0 8px var(--nord-blue);
}

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

.lang-switch {
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--text-muted);
  font-size: 0.88rem;
  cursor: pointer;
  padding: 6px 10px;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}
.lang-switch:hover {
  color: var(--text-white);
  background: rgba(255, 255, 255, 0.05);
}

.mobile-nav-toggle {
  display: none;
  background: none;
  border: 1px solid var(--nord-border);
  color: var(--text-white);
  padding: 8px;
  border-radius: var(--radius-sm);
  cursor: pointer;
}

/* ==============================================================================
   Buttons & Badges
   ============================================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  padding: 11px 22px;
  border-radius: var(--radius-full);
  border: 1px solid transparent;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-decoration: none;
  white-space: nowrap;
}

.btn-primary {
  background: linear-gradient(135deg, #4687FF, #1E60E0);
  color: #FFFFFF;
  box-shadow: 0 4px 14px rgba(70, 135, 255, 0.35);
}
.btn-primary:hover {
  background: linear-gradient(135deg, #5A96FF, #296DF0);
  box-shadow: 0 6px 20px rgba(70, 135, 255, 0.55);
  transform: translateY(-1px);
  color: #FFFFFF;
}

.btn-secondary {
  background: rgba(255, 255, 255, 0.08);
  color: var(--text-white);
  border: 1px solid var(--nord-border);
}
.btn-secondary:hover {
  background: rgba(255, 255, 255, 0.14);
  border-color: rgba(255, 255, 255, 0.25);
  color: #FFFFFF;
}

.btn-sm {
  padding: 7px 16px;
  font-size: 0.85rem;
  border-radius: var(--radius-full);
}

.btn-lg {
  padding: 14px 32px;
  font-size: 1.05rem;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.78rem;
  font-weight: 700;
  padding: 4px 10px;
  border-radius: var(--radius-full);
  text-transform: uppercase;
  letter-spacing: 0.03em;
}
.badge-info {
  background: rgba(70, 135, 255, 0.15);
  color: #79ABFF;
  border: 1px solid rgba(70, 135, 255, 0.35);
}
.badge-success {
  background: rgba(16, 185, 129, 0.15);
  color: #34D399;
  border: 1px solid rgba(16, 185, 129, 0.35);
}
.badge-cyan {
  background: rgba(0, 210, 211, 0.15);
  color: #00D2D3;
  border: 1px solid rgba(0, 210, 211, 0.35);
}
.badge-warning {
  background: rgba(245, 158, 11, 0.15);
  color: #FBBF24;
  border: 1px solid rgba(245, 158, 11, 0.35);
}

/* ==============================================================================
   Bypass Notice Box (High-priority Conversion Banner)
   ============================================================================== */
.bypass-banner {
  background: linear-gradient(135deg, rgba(70, 135, 255, 0.15), rgba(0, 210, 211, 0.08));
  border: 1px solid rgba(70, 135, 255, 0.4);
  border-radius: var(--radius-lg);
  padding: 16px 22px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.25);
  margin-bottom: 24px;
}
.bypass-text {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 0.94rem;
  color: var(--text-white);
  flex-wrap: wrap;
}
.bypass-tag {
  background: var(--nord-blue);
  color: #FFFFFF;
  font-size: 0.75rem;
  font-weight: 800;
  padding: 3px 8px;
  border-radius: var(--radius-sm);
  letter-spacing: 0.05em;
  white-space: nowrap;
}

/* ==============================================================================
   Page Hero & Grids
   ============================================================================== */
.page-hero {
  padding: 64px 0 48px;
  position: relative;
}

.hero-tag {
  background: rgba(70, 135, 255, 0.12);
  color: #79ABFF;
  border: 1px solid rgba(70, 135, 255, 0.3);
  font-size: 0.82rem;
  font-weight: 700;
  padding: 5px 14px;
  border-radius: var(--radius-full);
  margin-bottom: 16px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 48px;
  align-items: center;
}

.hero-title {
  font-size: 2.85rem;
  font-weight: 800;
  line-height: 1.15;
  color: var(--text-white);
  letter-spacing: -0.02em;
  margin-bottom: 20px;
}
.hero-title span {
  background: linear-gradient(135deg, #4687FF 20%, #00D2D3 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-desc {
  font-size: 1.12rem;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 32px;
}

.hero-metrics-bar {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
  background: var(--nord-navy-surface);
  border: 1px solid var(--nord-border);
  border-radius: var(--radius-lg);
  padding: 20px 24px;
  margin-top: 36px;
}
.metric-item {
  text-align: center;
}
.metric-val {
  font-size: 1.85rem;
  font-weight: 800;
  color: var(--nord-blue);
  font-family: var(--font-mono);
  line-height: 1.2;
}
.metric-val.cyan {
  color: var(--nord-cyan);
}
.metric-val.green {
  color: var(--nord-green);
}
.metric-label {
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-top: 4px;
}

/* Hero Feature Card (Interactive protocol showcase) */
.hero-interactive-card {
  background: var(--nord-navy-surface);
  border: 1px solid var(--nord-border);
  border-radius: var(--radius-xl);
  padding: 32px;
  box-shadow: var(--shadow-lg);
  position: relative;
  overflow: hidden;
}
.hero-interactive-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--nord-blue), var(--nord-cyan));
}

/* ==============================================================================
   Feature Cards & Pillars
   ============================================================================== */
.section {
  padding: 72px 0;
}

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

.feature-card {
  background: var(--nord-navy-surface);
  border: 1px solid var(--nord-border);
  border-radius: var(--radius-lg);
  padding: 32px 28px;
  transition: all var(--transition-normal);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}
.feature-card:hover {
  border-color: rgba(70, 135, 255, 0.4);
  transform: translateY(-4px);
  box-shadow: 0 12px 28px rgba(0, 0, 0, 0.45);
}

.feature-icon-wrapper {
  width: 54px;
  height: 54px;
  border-radius: var(--radius-md);
  background: rgba(70, 135, 255, 0.12);
  color: var(--nord-blue);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
  border: 1px solid rgba(70, 135, 255, 0.25);
}

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

.feature-desc {
  font-size: 0.95rem;
  color: var(--text-secondary);
  line-height: 1.65;
  margin-bottom: 16px;
}

/* ==============================================================================
   Download Cards Matrix (Clean, Equal Height, Wrapped Badges)
   ============================================================================== */
.download-cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 24px;
}

.platform-card {
  background: var(--nord-navy-surface);
  border: 1px solid var(--nord-border);
  border-radius: var(--radius-lg);
  padding: 28px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: all var(--transition-normal);
}
.platform-card:hover {
  border-color: rgba(70, 135, 255, 0.45);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.35);
}

.platform-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 18px;
  flex-wrap: wrap;
  gap: 10px;
}

.platform-card-title {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-white);
}

.platform-specs-box {
  background: var(--nord-navy-base);
  border: 1px solid var(--nord-border);
  border-radius: var(--radius-md);
  padding: 14px 16px;
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.65;
  margin-bottom: 20px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.platform-specs-box div {
  word-break: break-word;
  overflow-wrap: break-word;
}
.platform-specs-box strong {
  color: var(--text-white);
}

.version-badge {
  background: rgba(0, 210, 211, 0.12);
  color: var(--nord-cyan);
  border: 1px solid rgba(0, 210, 211, 0.3);
  font-size: 0.78rem;
  font-family: var(--font-mono);
  padding: 3px 8px;
  border-radius: var(--radius-sm);
  font-weight: 600;
}

.download-btn-group {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

/* ==============================================================================
   FAQ Accordion
   ============================================================================== */
.faq-list {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.faq-item {
  background: var(--nord-navy-surface);
  border: 1px solid var(--nord-border);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: border-color var(--transition-fast);
}
.faq-item.active {
  border-color: rgba(70, 135, 255, 0.5);
}

.faq-question {
  width: 100%;
  padding: 20px 24px;
  background: none;
  border: none;
  color: var(--text-white);
  font-size: 1.05rem;
  font-weight: 600;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  cursor: pointer;
  text-align: left;
}

.faq-icon {
  font-size: 1.3rem;
  color: var(--nord-blue);
  transition: transform var(--transition-fast);
  flex-shrink: 0;
}
.faq-item.active .faq-icon {
  transform: rotate(45deg);
  color: var(--nord-cyan);
}

.faq-answer {
  display: none;
  padding: 0 24px 22px;
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.7;
  border-top: 1px solid rgba(255, 255, 255, 0.05);
}
.faq-item.active .faq-answer {
  display: block;
}

/* ==============================================================================
   Help Search & Modal
   ============================================================================== */
.search-input {
  width: 100%;
  background: var(--nord-navy-surface);
  border: 1px solid var(--nord-border);
  border-radius: var(--radius-full);
  padding: 14px 24px;
  color: var(--text-white);
  font-size: 1rem;
  outline: none;
  transition: all var(--transition-fast);
}
.search-input:focus {
  border-color: var(--nord-blue);
  box-shadow: 0 0 16px var(--nord-blue-glow);
}

.help-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 20px;
}

.help-article-card {
  background: var(--nord-navy-surface);
  border: 1px solid var(--nord-border);
  border-radius: var(--radius-md);
  padding: 22px;
  transition: all var(--transition-fast);
}
.help-article-card:hover {
  border-color: rgba(70, 135, 255, 0.4);
  background: var(--nord-navy-card);
}

/* Modal */
.nord-modal {
  position: fixed;
  inset: 0;
  z-index: 2000;
  background: rgba(8, 14, 28, 0.85);
  backdrop-filter: blur(8px);
  display: none;
  align-items: center;
  justify-content: center;
  padding: 20px;
}
.nord-modal.active {
  display: flex;
}
.modal-content {
  background: var(--nord-navy-surface);
  border: 1px solid var(--nord-border);
  border-radius: var(--radius-lg);
  width: 100%;
  max-width: 680px;
  max-height: 85vh;
  overflow-y: auto;
  box-shadow: var(--shadow-lg);
  padding: 32px;
}
.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 20px;
}
.modal-close-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 1.5rem;
  cursor: pointer;
  line-height: 1;
}
.modal-close-btn:hover {
  color: var(--text-white);
}

/* Toast */
.nord-toast {
  position: fixed;
  bottom: 24px;
  right: 24px;
  background: #122146;
  border: 1px solid var(--nord-blue);
  color: #FFFFFF;
  padding: 12px 20px;
  border-radius: var(--radius-md);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.6);
  z-index: 3000;
  display: none;
  font-size: 0.92rem;
}
.nord-toast.show {
  display: block;
  animation: fadeIn 0.25s ease;
}

/* ==============================================================================
   Footer
   ============================================================================== */
.nord-footer {
  background: var(--nord-navy-deep);
  border-top: 1px solid var(--nord-border);
  padding: 64px 0 32px;
  margin-top: auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.5fr repeat(3, 1fr);
  gap: 40px;
  margin-bottom: 48px;
}

.footer-col h4 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-white);
  margin-bottom: 18px;
  letter-spacing: 0.02em;
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.footer-links a {
  color: var(--text-muted);
  font-size: 0.9rem;
}
.footer-links a:hover {
  color: var(--nord-blue);
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  padding-top: 28px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
  font-size: 0.85rem;
  color: var(--text-muted);
}
.footer-bottom-links {
  list-style: none;
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
}
.footer-bottom-links a {
  color: var(--text-muted);
}
.footer-bottom-links a:hover {
  color: var(--nord-cyan);
}

/* ==============================================================================
   Responsive Queries
   ============================================================================== */
@media (max-width: 960px) {
  .nav-links {
    display: none;
  }
  .nav-links.mobile-open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 72px;
    left: 0;
    right: 0;
    background: var(--nord-navy-surface);
    padding: 24px 32px;
    border-bottom: 2px solid var(--nord-blue);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.5);
    gap: 16px;
    z-index: 999;
  }
  .mobile-nav-toggle {
    display: flex;
  }
  .hero-grid {
    grid-template-columns: 1fr;
    text-align: center;
  }
  .hero-desc {
    margin-left: auto;
    margin-right: auto;
  }
  .hero-metrics-bar {
    grid-template-columns: repeat(2, 1fr);
  }
  .footer-grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 640px) {
  .hero-title {
    font-size: 2.15rem;
  }
  .hero-metrics-bar {
    grid-template-columns: 1fr;
  }
  .footer-grid {
    grid-template-columns: 1fr;
  }
  .bypass-banner {
    flex-direction: column;
    text-align: center;
  }
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}