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

:root {
  --primary: #1a73e8;
  --primary-dark: #1557b0;
  --secondary: #5f6368;
  --success: #1e8e3e;
  --border: #dadce0;
  --bg-light: #f8f9fa;
  --bg-white: #ffffff;
  --text-dark: #202124;
  --text-gray: #5f6368;
  --shadow-sm: 0 1px 2px 0 rgba(60,64,67,0.3), 0 1px 3px 1px rgba(60,64,67,0.15);
  --shadow-md: 0 1px 3px 0 rgba(60,64,67,0.3), 0 4px 8px 3px rgba(60,64,67,0.15);
  --shadow-lg: 0 2px 6px 2px rgba(60,64,67,0.15), 0 8px 24px 4px rgba(60,64,67,0.15);
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  line-height: 1.6;
  color: var(--text-dark);
  background: var(--bg-white);
}

/* Navigation */
.nav-bar {
  background: var(--bg-white);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-sm);
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 20px;
  font-weight: 600;
  color: var(--text-dark);
  text-decoration: none;
}

.nav-links {
  display: flex;
  gap: 8px;
  list-style: none;
}

.nav-links a {
  display: block;
  padding: 8px 16px;
  color: var(--text-gray);
  text-decoration: none;
  border-radius: 8px;
  transition: all 0.2s;
  font-size: 14px;
  font-weight: 500;
}

.nav-links a:hover {
  background: var(--bg-light);
  color: var(--text-dark);
}

.nav-links a.active {
  background: var(--primary);
  color: white;
}

/* Hero Section */
.hero {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: 80px 24px;
  text-align: center;
}

.hero-content {
  max-width: 800px;
  margin: 0 auto;
}

.hero h1 {
  font-size: 48px;
  font-weight: 700;
  margin-bottom: 16px;
  line-height: 1.2;
}

.hero-subtitle {
  font-size: 20px;
  opacity: 0.95;
  margin-bottom: 32px;
  line-height: 1.5;
}

.hero-cta {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 32px;
  background: white;
  color: var(--primary);
  border: none;
  border-radius: 24px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  box-shadow: var(--shadow-md);
  transition: all 0.2s;
}

.hero-cta:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.hero-cta:disabled {
  opacity: 0.7;
  cursor: not-allowed;
}

/* Container */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

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

.section-title {
  font-size: 36px;
  font-weight: 700;
  text-align: center;
  margin-bottom: 16px;
  color: var(--text-dark);
}

.section-subtitle {
  font-size: 18px;
  text-align: center;
  color: var(--text-gray);
  margin-bottom: 48px;
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
}

/* Feature Grid */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 32px;
  margin-top: 48px;
}

.feature-card {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 32px;
  transition: all 0.3s;
}

.feature-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-4px);
}

.feature-icon {
  width: 48px;
  height: 48px;
  margin-bottom: 16px;
  color: var(--primary);
}

.feature-card h3 {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 12px;
  color: var(--text-dark);
}

.feature-card p {
  color: var(--text-gray);
  line-height: 1.6;
}

/* Platform Cards */
.platform-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 24px;
  margin-top: 48px;
}

.platform-card {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 32px;
  text-align: center;
  transition: all 0.3s;
}

.platform-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--primary);
}

.platform-card.featured {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  border: none;
}

.platform-card.featured h3,
.platform-card.featured p {
  color: white;
}

.platform-icon {
  width: 64px;
  height: 64px;
  margin: 0 auto 16px;
}

.platform-card h3 {
  font-size: 22px;
  font-weight: 600;
  margin-bottom: 8px;
}

.platform-card p {
  color: var(--text-gray);
  margin-bottom: 20px;
  font-size: 14px;
}

.btn-download {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  background: var(--primary);
  color: white;
  border: none;
  border-radius: 8px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  width: 100%;
  justify-content: center;
}

.btn-download:hover:not(:disabled) {
  background: var(--primary-dark);
}

.btn-download:disabled {
  opacity: 0.7;
  cursor: not-allowed;
}

.platform-card.featured .btn-download {
  background: white;
  color: var(--primary);
}

.platform-card.featured .btn-download:hover:not(:disabled) {
  background: var(--bg-light);
}

/* Reviews */
.reviews-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 24px;
  margin-top: 48px;
}

.review-card {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 24px;
}

.review-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 16px;
}

.review-avatar {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-weight: 600;
  font-size: 18px;
}

.review-author h4 {
  font-size: 16px;
  font-weight: 600;
  color: var(--text-dark);
}

.review-stars {
  color: #fbbc04;
  font-size: 14px;
}

.review-card p {
  color: var(--text-gray);
  line-height: 1.6;
  font-style: italic;
}

/* FAQ */
.faq-container {
  max-width: 800px;
  margin: 48px auto 0;
}

.faq-item {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: 8px;
  margin-bottom: 16px;
  overflow: hidden;
}

.faq-question {
  width: 100%;
  text-align: left;
  padding: 20px 24px;
  background: none;
  border: none;
  font-size: 16px;
  font-weight: 600;
  color: var(--text-dark);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: background 0.2s;
}

.faq-question:hover {
  background: var(--bg-light);
}

.faq-icon {
  width: 20px;
  height: 20px;
  transition: transform 0.3s;
  flex-shrink: 0;
}

.faq-item.active .faq-icon {
  transform: rotate(180deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
}

.faq-answer-content {
  padding: 0 24px 20px;
  color: var(--text-gray);
  line-height: 1.6;
}

.faq-item.active .faq-answer {
  max-height: 500px;
}

/* Stats */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 32px;
  margin: 48px 0;
  text-align: center;
}

.stat-item h3 {
  font-size: 48px;
  font-weight: 700;
  color: var(--primary);
  margin-bottom: 8px;
}

.stat-item p {
  color: var(--text-gray);
  font-size: 16px;
}

/* Footer */
.footer {
  background: var(--bg-light);
  border-top: 1px solid var(--border);
  padding: 48px 24px;
  margin-top: 80px;
}

.footer-content {
  max-width: 1200px;
  margin: 0 auto;
  text-align: center;
}

.footer-security {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  color: var(--success);
  font-weight: 600;
  margin-bottom: 16px;
  font-size: 15px;
}

.footer-security svg {
  width: 20px;
  height: 20px;
}

.footer-text {
  color: var(--text-gray);
  font-size: 14px;
  line-height: 1.6;
}

/* Comparison Table */
.comparison-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 48px;
  background: var(--bg-white);
  border-radius: 12px;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

.comparison-table th,
.comparison-table td {
  padding: 16px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

.comparison-table th {
  background: var(--bg-light);
  font-weight: 600;
  color: var(--text-dark);
}

.comparison-table tr:last-child td {
  border-bottom: none;
}

.comparison-table tr:hover {
  background: var(--bg-light);
}

/* Steps */
.steps-container {
  max-width: 900px;
  margin: 48px auto 0;
}

.step-item {
  display: flex;
  gap: 24px;
  margin-bottom: 32px;
  padding: 24px;
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: 12px;
  transition: all 0.3s;
}

.step-item:hover {
  box-shadow: var(--shadow-md);
}

.step-number {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--primary);
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  font-weight: 700;
  flex-shrink: 0;
}

.step-content h3 {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--text-dark);
}

.step-content p {
  color: var(--text-gray);
  line-height: 1.6;
}

/* Article Layout (zh-cn.html) */
.article-hero {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: 60px 24px;
  text-align: center;
}

.article-hero h1 {
  font-size: 42px;
  font-weight: 700;
  margin-bottom: 16px;
}

.article-hero p {
  font-size: 18px;
  opacity: 0.95;
}

.article-layout {
  display: grid;
  grid-template-columns: 1fr 280px;
  gap: 48px;
  max-width: 1200px;
  margin: 48px auto;
  padding: 0 24px;
}

.article-content {
  min-width: 0;
}

.article-content h2 {
  font-size: 28px;
  font-weight: 700;
  margin: 48px 0 16px;
  color: var(--text-dark);
}

.article-content h3 {
  font-size: 22px;
  font-weight: 600;
  margin: 32px 0 12px;
  color: var(--text-dark);
}

.article-content p {
  color: var(--text-gray);
  line-height: 1.8;
  margin-bottom: 16px;
}

.article-content ul,
.article-content ol {
  margin: 16px 0;
  padding-left: 24px;
  color: var(--text-gray);
}

.article-content li {
  margin-bottom: 8px;
  line-height: 1.6;
}

.article-sidebar {
  position: sticky;
  top: 80px;
  height: fit-content;
}

.toc {
  background: var(--bg-light);
  border-radius: 12px;
  padding: 24px;
}

.toc h3 {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 16px;
  color: var(--text-dark);
}

.toc ul {
  list-style: none;
}

.toc li {
  margin-bottom: 8px;
}

.toc a {
  color: var(--text-gray);
  text-decoration: none;
  font-size: 14px;
  transition: color 0.2s;
}

.toc a:hover {
  color: var(--primary);
}

.cta-box {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: 48px;
  border-radius: 12px;
  text-align: center;
  margin: 48px 0;
}

.cta-box h2 {
  font-size: 32px;
  font-weight: 700;
  margin-bottom: 16px;
}

.cta-box p {
  font-size: 18px;
  margin-bottom: 24px;
  opacity: 0.95;
}

.cta-box a {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 32px;
  background: white;
  color: var(--primary);
  text-decoration: none;
  border-radius: 24px;
  font-size: 16px;
  font-weight: 600;
  transition: all 0.2s;
}

.cta-box a:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

/* Tabs */
.tabs {
  display: flex;
  gap: 8px;
  border-bottom: 2px solid var(--border);
  margin-bottom: 24px;
}

.tab-btn {
  padding: 12px 24px;
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  color: var(--text-gray);
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  margin-bottom: -2px;
}

.tab-btn:hover {
  color: var(--text-dark);
}

.tab-btn.active {
  color: var(--primary);
  border-bottom-color: var(--primary);
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

/* Spin Animation */
@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

/* Responsive */
@media (max-width: 768px) {
  .hero h1 {
    font-size: 36px;
  }
  
  .hero-subtitle {
    font-size: 18px;
  }
  
  .section-title {
    font-size: 28px;
  }
  
  .feature-grid,
  .platform-grid,
  .reviews-grid {
    grid-template-columns: 1fr;
  }
  
  .article-layout {
    grid-template-columns: 1fr;
  }
  
  .article-sidebar {
    position: static;
  }
  
  .nav-links {
    gap: 4px;
  }
  
  .nav-links a {
    padding: 6px 12px;
    font-size: 13px;
  }
}