/* ═══════════════════════════════════════
   咕嘟科技 Gudu Tech — 设计系统
   ═══════════════════════════════════════ */

:root {
  --primary: #2563EB;
  --primary-dark: #1D4ED8;
  --primary-light: #DBEAFE;
  --accent: #F59E0B;
  --accent-dark: #D97706;
  --success: #10B981;
  --success-light: #D1FAE5;
  --danger: #EF4444;
  --text: #1F2937;
  --text-secondary: #6B7280;
  --text-light: #9CA3AF;
  --bg: #FFFFFF;
  --bg-alt: #F8FAFC;
  --bg-dark: #111827;
  --border: #E5E7EB;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -2px rgba(0,0,0,0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -4px rgba(0,0,0,0.1);
  --shadow-xl: 0 20px 25px -5px rgba(0,0,0,0.1), 0 8px 10px -6px rgba(0,0,0,0.1);
  --radius: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;
}

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

html { scroll-behavior: smooth; font-size: 16px; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

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

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

/* ═══ 容器 ═══ */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}
.container-sm { max-width: 800px; }
.container-lg { max-width: 1400px; }

/* ═══ 导航栏 ═══ */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255,255,255,0.95);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  padding: 0 24px;
}
.nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}
.nav-logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text);
  display: flex;
  align-items: center;
  gap: 8px;
}
.nav-logo span { color: var(--primary); }
.nav-links {
  display: flex;
  align-items: center;
  gap: 32px;
  list-style: none;
}
.nav-links a {
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  transition: color 0.2s;
}
.nav-links a:hover, .nav-links a.active { color: var(--primary); }
.nav-cta {
  background: var(--primary);
  color: #FFF !important;
  padding: 8px 20px;
  border-radius: var(--radius);
  font-weight: 600;
  transition: background 0.2s;
}
.nav-cta:hover { background: var(--primary-dark); }

/* ═══ 按钮 ═══ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 28px;
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: var(--radius);
  border: 2px solid transparent;
  cursor: pointer;
  transition: all 0.2s;
  text-decoration: none;
  line-height: 1.4;
}
.btn-primary {
  background: var(--primary);
  color: #FFF;
  border-color: var(--primary);
}
.btn-primary:hover {
  background: var(--primary-dark);
  border-color: var(--primary-dark);
  color: #FFF;
}
.btn-accent {
  background: var(--accent);
  color: #FFF;
  border-color: var(--accent);
}
.btn-accent:hover {
  background: var(--accent-dark);
  border-color: var(--accent-dark);
  color: #FFF;
}
.btn-outline {
  background: transparent;
  color: var(--primary);
  border-color: var(--primary);
}
.btn-outline:hover {
  background: var(--primary);
  color: #FFF;
}
.btn-lg { padding: 16px 36px; font-size: 1.05rem; border-radius: var(--radius-lg); }
.btn-sm { padding: 8px 18px; font-size: 0.85rem; }

/* ═══ Footer ═══ */
.footer {
  background: var(--bg-dark);
  color: #D1D5DB;
  padding: 64px 0 32px;
}
.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}
.footer-brand h3 { color: #FFF; font-size: 1.25rem; margin-bottom: 12px; }
.footer-brand p { font-size: 0.9rem; line-height: 1.7; }
.footer-col h4 { color: #FFF; font-size: 0.95rem; margin-bottom: 16px; }
.footer-col ul { list-style: none; }
.footer-col li { margin-bottom: 10px; }
.footer-col a { color: #9CA3AF; font-size: 0.9rem; transition: color 0.2s; }
.footer-col a:hover { color: #FFF; }
.footer-bottom {
  border-top: 1px solid #374151;
  padding-top: 24px;
  text-align: center;
  font-size: 0.85rem;
  color: #6B7280;
}

/* ═══ Section 通用 ═══ */
.section { padding: 80px 0; }
.section-alt { background: var(--bg-alt); }
.section-dark { background: var(--bg-dark); color: #FFF; }
.section-header { text-align: center; margin-bottom: 56px; }
.section-header h2 {
  font-size: 2.25rem;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 12px;
}
.section-header p {
  font-size: 1.1rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
}
.section-dark .section-header h2 { color: #FFF; }
.section-dark .section-header p { color: #9CA3AF; }

/* ═══ 标签 ═══ */
.badge {
  display: inline-block;
  padding: 4px 12px;
  font-size: 0.8rem;
  font-weight: 600;
  border-radius: 100px;
  background: var(--primary-light);
  color: var(--primary);
  margin-bottom: 16px;
}

/* ═══ 卡片 ═══ */
.card {
  background: #FFF;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
  transition: box-shadow 0.3s, transform 0.3s;
}
.card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

/* ═══ 定价卡片 ═══ */
.pricing-card {
  background: #FFF;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 40px 32px;
  text-align: center;
  transition: all 0.3s;
  position: relative;
}
.pricing-card.featured {
  border-color: var(--primary);
  box-shadow: var(--shadow-lg);
  transform: scale(1.05);
}
.pricing-card.featured::before {
  content: '推荐';
  position: absolute;
  top: -12px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--primary);
  color: #FFF;
  padding: 4px 16px;
  border-radius: 100px;
  font-size: 0.8rem;
  font-weight: 600;
}
.pricing-name { font-size: 1.1rem; font-weight: 700; margin-bottom: 8px; }
.pricing-desc { color: var(--text-secondary); font-size: 0.9rem; margin-bottom: 24px; }
.pricing-price { font-size: 2.5rem; font-weight: 800; color: var(--text); }
.pricing-price span { font-size: 1rem; font-weight: 500; color: var(--text-secondary); }
.pricing-features { list-style: none; text-align: left; margin: 32px 0; }
.pricing-features li {
  padding: 8px 0;
  font-size: 0.9rem;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 10px;
}
.pricing-features li::before {
  content: '\2713';
  color: var(--success);
  font-weight: 700;
  font-size: 1rem;
}

/* ═══ 响应式 ═══ */
@media (max-width: 768px) {
  .section { padding: 48px 0; }
  .section-header h2 { font-size: 1.75rem; }
  .footer-grid { grid-template-columns: 1fr 1fr; gap: 32px; }
  .nav-links { display: none; }
  .pricing-card.featured { transform: none; }
}