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

:root {
  --primary: #2b77e5;
  --primary-dark: #1a5fc4;
  --accent: #e8463a;
  --text: #333;
  --text-light: #666;
  --bg: #f5f7fa;
  --white: #fff;
  --border: #e8ecf0;
  --shadow: 0 4px 20px rgba(0,0,0,.08);
  --radius: 12px;
}

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  color: var(--text);
  line-height: 1.7;
  background: var(--bg);
}

a { color: var(--primary); text-decoration: none; transition: color .2s; }
a:hover { color: var(--primary-dark); }

img { max-width: 100%; height: auto; }

.container { max-width: 1140px; margin: 0 auto; padding: 0 20px; }

/* Header */
.site-header {
  background: var(--white);
  box-shadow: 0 1px 6px rgba(0,0,0,.06);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 22px;
  font-weight: 700;
  color: var(--primary);
}

.logo-icon {
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, var(--primary), #5a9cf5);
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--white);
  font-size: 18px;
  font-weight: bold;
}

.main-nav { display: flex; gap: 28px; list-style: none; }
.main-nav a { color: var(--text); font-size: 15px; font-weight: 500; }
.main-nav a:hover, .main-nav a.active { color: var(--primary); }

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 24px;
  border-radius: 8px;
  font-size: 15px;
  font-weight: 600;
  border: none;
  cursor: pointer;
  transition: all .2s;
}

.btn-primary {
  background: var(--accent);
  color: var(--white);
}
.btn-primary:hover { background: #d03830; color: var(--white); transform: translateY(-1px); }

.btn-outline {
  background: transparent;
  color: var(--primary);
  border: 2px solid var(--primary);
}
.btn-outline:hover { background: var(--primary); color: var(--white); }

.btn-lg { padding: 14px 36px; font-size: 16px; }

/* Hero */
.hero {
  background: linear-gradient(135deg, #1a5fc4 0%, #2b77e5 50%, #4a90e8 100%);
  color: var(--white);
  padding: 80px 0 100px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  top: -50%;
  right: -20%;
  width: 600px;
  height: 600px;
  background: rgba(255,255,255,.06);
  border-radius: 50%;
}

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

.hero-sub {
  font-size: 18px;
  opacity: .92;
  max-width: 640px;
  margin: 0 auto 36px;
  position: relative;
}

.hero-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
  position: relative;
}

.hero .btn-outline {
  border-color: var(--white);
  color: var(--white);
}
.hero .btn-outline:hover { background: var(--white); color: var(--primary); }

/* Features */
.section { padding: 72px 0; }
.section-title {
  text-align: center;
  font-size: 32px;
  font-weight: 700;
  margin-bottom: 12px;
}
.section-desc {
  text-align: center;
  color: var(--text-light);
  max-width: 560px;
  margin: 0 auto 48px;
  font-size: 16px;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 28px;
}

.feature-card {
  background: var(--white);
  border-radius: var(--radius);
  padding: 32px 28px;
  box-shadow: var(--shadow);
  transition: transform .2s;
}
.feature-card:hover { transform: translateY(-4px); }

.feature-icon {
  width: 52px;
  height: 52px;
  background: linear-gradient(135deg, #e8f0fe, #d4e4fc);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;
  margin-bottom: 18px;
}

.feature-card h3 { font-size: 18px; margin-bottom: 10px; }
.feature-card p { color: var(--text-light); font-size: 14px; }

/* Stats */
.stats-bar {
  background: var(--white);
  padding: 48px 0;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

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

.stat-num {
  font-size: 36px;
  font-weight: 700;
  color: var(--primary);
}
.stat-label { color: var(--text-light); font-size: 14px; margin-top: 4px; }

/* Articles preview */
.articles-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 28px;
}

.article-card {
  background: var(--white);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
  transition: transform .2s;
}
.article-card:hover { transform: translateY(-3px); }

.article-card-body { padding: 24px; }
.article-card .tag {
  display: inline-block;
  background: #e8f0fe;
  color: var(--primary);
  font-size: 12px;
  padding: 3px 10px;
  border-radius: 4px;
  margin-bottom: 10px;
}
.article-card h3 { font-size: 17px; margin-bottom: 8px; line-height: 1.5; }
.article-card h3 a { color: var(--text); }
.article-card h3 a:hover { color: var(--primary); }
.article-card p { color: var(--text-light); font-size: 14px; margin-bottom: 12px; }
.article-meta { font-size: 12px; color: #999; }

/* FAQ */
.faq-list { max-width: 760px; margin: 0 auto; }
.faq-item {
  background: var(--white);
  border-radius: var(--radius);
  margin-bottom: 12px;
  box-shadow: var(--shadow);
  overflow: hidden;
}
.faq-q {
  padding: 20px 24px;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.faq-q::after { content: "+"; font-size: 20px; color: var(--primary); }
.faq-item.open .faq-q::after { content: "−"; }
.faq-a {
  padding: 0 24px 20px;
  color: var(--text-light);
  font-size: 14px;
  display: none;
}
.faq-item.open .faq-a { display: block; }

/* Download page */
.download-hero {
  background: linear-gradient(135deg, #1a5fc4, #2b77e5);
  color: var(--white);
  padding: 60px 0;
  text-align: center;
}

.download-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
  margin-top: -40px;
  position: relative;
  z-index: 2;
  padding-bottom: 60px;
}

.download-card {
  background: var(--white);
  border-radius: var(--radius);
  padding: 36px 28px;
  text-align: center;
  box-shadow: var(--shadow);
}

.download-card .platform-icon { font-size: 48px; margin-bottom: 16px; }
.download-card h3 { margin-bottom: 8px; }
.download-card p { color: var(--text-light); font-size: 14px; margin-bottom: 20px; }

/* Article page */
.article-header {
  background: var(--white);
  padding: 48px 0 32px;
  border-bottom: 1px solid var(--border);
}
.article-header h1 { font-size: 32px; margin-bottom: 12px; line-height: 1.4; }
.article-content {
  background: var(--white);
  padding: 40px 0 60px;
}
.article-body {
  max-width: 760px;
  margin: 0 auto;
  font-size: 16px;
}
.article-body h2 { font-size: 22px; margin: 32px 0 14px; color: var(--text); }
.article-body h3 { font-size: 18px; margin: 24px 0 10px; }
.article-body p { margin-bottom: 16px; color: #444; }
.article-body ul, .article-body ol { margin: 12px 0 16px 24px; color: #444; }
.article-body li { margin-bottom: 8px; }

.breadcrumb {
  font-size: 13px;
  color: var(--text-light);
  margin-bottom: 16px;
}
.breadcrumb a { color: var(--text-light); }
.breadcrumb a:hover { color: var(--primary); }

/* Footer */
.site-footer {
  background: #2c3e50;
  color: #bdc3c7;
  padding: 48px 0 24px;
}
.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 32px;
  margin-bottom: 32px;
}
.footer-col h4 { color: var(--white); margin-bottom: 14px; font-size: 15px; }
.footer-col ul { list-style: none; }
.footer-col li { margin-bottom: 8px; }
.footer-col a { color: #bdc3c7; font-size: 14px; }
.footer-col a:hover { color: var(--white); }
.footer-bottom {
  border-top: 1px solid #3d5166;
  padding-top: 20px;
  text-align: center;
  font-size: 13px;
}

/* Mobile */
.mobile-menu-btn { display: none; background: none; border: none; font-size: 24px; cursor: pointer; color: var(--text); }

@media (max-width: 768px) {
  .main-nav { display: none; }
  .main-nav.open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--white);
    padding: 16px 20px;
    box-shadow: var(--shadow);
    gap: 12px;
  }
  .mobile-menu-btn { display: block; }
  .hero h1 { font-size: 28px; }
  .hero { padding: 56px 0 72px; }
  .section-title { font-size: 24px; }
  .article-header h1 { font-size: 24px; }
}