:root {
  /* 深色蓝调 */
  --primary: #2481CC;
  --primary-dark: #1976D2;
  --primary-light: #42A5F5;
  --gradient-start: #1E88E5;
  --gradient-end: #1565C0;
  
  --text: #212121;
  --text-light: #616161;
  --bg: #FAFAFA;
  --bg-white: #FFFFFF;
  --border: #E0E0E0;
  --shadow: rgba(36, 129, 204, 0.12);
  
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 20px;
  
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.12);
  
  --transition-fast: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Helvetica Neue', sans-serif;
  color: var(--text);
  background-color: var(--bg);
  line-height: 1.6;
}

.container {
  width: 100%;
  padding: 0 20px;
  margin: 0 auto;
}

@media (min-width: 768px) {
  .container {
    max-width: 720px;
  }
}

@media (min-width: 1024px) {
  .container {
    max-width: 960px;
  }
}

@media (min-width: 1280px) {
  .container {
    max-width: 1200px;
  }
}

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

.navbar {
  padding: 12px 0;
}

.navbar .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--primary);
  font-weight: 700;
  font-size: 20px;
  transition: all var(--transition-fast);
}

.logo:hover {
  color: var(--primary-dark);
  transform: scale(1.05);
}

.logo-icon {
  color: var(--primary);
}

.logo-text {
  background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.nav-menu {
  display: flex;
  list-style: none;
  gap: 40px;
  margin: 0;
}

.nav-menu a {
  text-decoration: none;
  color: var(--text);
  font-weight: 500;
  transition: color var(--transition-fast);
}

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

.btn-nav-download {
  background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
  color: white;
  padding: 10px 24px;
  border-radius: 50px;
  text-decoration: none;
  font-weight: 600;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.btn-nav-download:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px var(--shadow);
}

@media (max-width: 768px) {
  .nav-menu {
    display: none;
  }
}

.hero {
  padding: 100px 0;
  text-align: center;
  background: linear-gradient(135deg, rgba(30, 136, 229, 0.1), rgba(21, 101, 192, 0.05));
}

.hero h1 {
  font-size: clamp(32px, 8vw, 56px);
  font-weight: 700;
  margin-bottom: 20px;
  background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 20px;
  color: var(--text-light);
  margin-bottom: 40px;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.btn-download-solid {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  padding: 16px 48px;
  background: var(--primary);
  color: #fff;
  border-radius: 50px;
  font-size: 17px;
  font-weight: 600;
  text-decoration: none;
  border: none;
  transition: all var(--transition-base);
  cursor: pointer;
}

.btn-download-solid:hover {
  background: var(--primary-dark);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.15);
}

.intro-section {
  padding: 60px 0;
  background: var(--bg-white);
}

.intro-card {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 40px;
  margin-bottom: 40px;
  transition: all var(--transition-base);
}

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

.intro-card h2 {
  font-size: 28px;
  margin-bottom: 20px;
  color: var(--text);
}

.intro-card p {
  color: var(--text-light);
  font-size: 16px;
  line-height: 1.8;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
  padding: 60px 0;
}

.feature-card {
  background: var(--bg-white);
  border-radius: var(--radius-lg);
  padding: 32px;
  text-align: center;
  transition: all var(--transition-base);
  border: 1px solid var(--border);
}

.feature-card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-lg);
  border-color: var(--primary);
}

.feature-icon {
  font-size: 48px;
  margin-bottom: 20px;
}

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

.feature-card p {
  color: var(--text-light);
  font-size: 15px;
  line-height: 1.6;
}

.section-title {
  text-align: center;
  font-size: 36px;
  margin-bottom: 50px;
  color: var(--text);
}

.section-white {
  padding: 60px 0;
  background: var(--bg-white);
}

.section-gray {
  padding: 60px 0;
  background: var(--bg);
}

.two-column {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
  margin: 60px 0;
}

.two-column h3 {
  font-size: 24px;
  margin-bottom: 20px;
  color: var(--text);
}

.two-column ul {
  list-style: none;
}

.two-column ul li {
  padding: 12px 0;
  color: var(--text-light);
  font-size: 16px;
  display: flex;
  align-items: center;
  gap: 12px;
}

.two-column ul li:before {
  content: "✓";
  color: var(--primary);
  font-weight: bold;
  font-size: 18px;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 40px;
  text-align: center;
  margin: 60px 0;
}

.stat-item {
  padding: 20px;
}

.stat-number {
  font-size: 48px;
  font-weight: 700;
  background: linear-gradient(135deg, var(--gradient-start), var(--gradient-end));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 12px;
}

.stat-label {
  font-size: 16px;
  color: var(--text-light);
}

.faq-item {
  max-width: 800px;
  margin: 0 auto 20px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  background: var(--bg-white);
  overflow: hidden;
}

.faq-question {
  padding: 20px;
  background: var(--bg);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-weight: 600;
  user-select: none;
  transition: background var(--transition-fast);
}

.faq-question:hover {
  background: linear-gradient(135deg, rgba(30, 136, 229, 0.1), rgba(21, 101, 192, 0.05));
}

.faq-toggle {
  font-size: 20px;
  transition: transform var(--transition-base);
}

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

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition-base);
}

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

.faq-answer-content {
  padding: 20px;
  color: var(--text-light);
  line-height: 1.8;
}

.footer {
  background: var(--text);
  color: rgba(255, 255, 255, 0.8);
  padding: 60px 0 20px;
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 40px;
  margin-bottom: 40px;
}

.footer-col h4 {
  color: white;
  margin-bottom: 16px;
  font-size: 16px;
}

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

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

.footer-col a {
  color: rgba(255, 255, 255, 0.6);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.footer-col a:hover {
  color: var(--primary-light);
}

.footer-logo {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 20px;
  font-weight: 700;
  color: white;
  margin-bottom: 12px;
}

.footer-logo svg {
  color: var(--primary-light);
}

.footer-desc {
  color: rgba(255, 255, 255, 0.6);
  font-size: 15px;
  line-height: 1.6;
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  padding-top: 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 20px;
}

.footer-links {
  display: flex;
  gap: 32px;
}

.footer-links a {
  color: rgba(255, 255, 255, 0.6);
  text-decoration: none;
  transition: color var(--transition-fast);
}

.footer-links a:hover {
  color: var(--primary-light);
}

@media (max-width: 768px) {
  .hero {
    padding: 50px 0;
  }
  
  .hero h1 {
    font-size: 28px;
  }
  
  .two-column {
    grid-template-columns: 1fr;
    gap: 40px;
  }
  
  .footer-bottom {
    flex-direction: column;
    align-items: flex-start;
  }
}

@keyframes float {
  0%, 100% {
    transform: translateY(0);
  }
  50% {
    transform: translateY(-10px);
  }
}

.plane-icon {
  animation: float 3s ease-in-out infinite;
}

@keyframes slideInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.feature-card {
  animation: slideInUp 0.5s ease-out forwards;
}