:root {
  --primary-color: #00d2ff;
  --secondary-color: #3a7bd5;
  --text-dark: #1f2937;
  --text-light: #6b7280;
  --text-white: #ffffff;
  --bg-color: #f9fafb;
  --card-bg: #ffffff;
  --border-color: #e5e7eb;
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --border-radius: 12px;
  --transition: all 0.3s ease;
}

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

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

a {
  text-decoration: none;
  color: inherit;
}

ul {
  list-style: none;
}

/* Container */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 12px 28px;
  border-radius: 50px;
  font-weight: 600;
  text-align: center;
  cursor: pointer;
  transition: var(--transition);
  border: none;
  font-size: 1rem;
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: var(--text-white);
  box-shadow: 0 4px 15px rgba(58, 123, 213, 0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(58, 123, 213, 0.4);
}

/* Header */
.header {
  background-color: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 100;
  border-bottom: 1px solid var(--border-color);
}

.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 70px;
}

.nav-links {
  display: none;
  gap: 30px;
}

.nav-links a {
  font-weight: 600;
  color: var(--text-dark);
  transition: var(--transition);
}

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

@media (min-width: 768px) {
  .nav-links {
    display: flex;
  }
}

.logo {
  font-size: 1.5rem;
  font-weight: 800;
  background: linear-gradient(to right, var(--primary-color), var(--secondary-color));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  display: flex;
  align-items: center;
  gap: 8px;
}

/* Hero Section */
.hero {
  padding: 80px 0 100px;
  background: linear-gradient(180deg, #f0f7ff 0%, #ffffff 100%);
  overflow: hidden;
}

.hero-content {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 40px;
  text-align: center;
}

.hero-text {
  flex: 1;
}

.hero-graphic {
  flex: 1;
  display: flex;
  justify-content: center;
  width: 100%;
}

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

@keyframes wobble {
  0% { transform: translateX(0) scaleX(1); }
  25% { transform: translateX(-5px) scaleX(1.05); }
  50% { transform: translateX(0) scaleX(1); }
  75% { transform: translateX(5px) scaleX(0.95); }
  100% { transform: translateX(0) scaleX(1); }
}

.tornado-svg {
  width: 100%;
  max-width: 350px;
  animation: sway 4s ease-in-out infinite;
}

.tornado-spin ellipse:nth-child(1) { animation: wobble 2s infinite ease-in-out; animation-delay: 0.1s; }
.tornado-spin ellipse:nth-child(2) { animation: wobble 2s infinite ease-in-out; animation-delay: 0.2s; }
.tornado-spin ellipse:nth-child(3) { animation: wobble 2s infinite ease-in-out; animation-delay: 0.3s; }
.tornado-spin ellipse:nth-child(4) { animation: wobble 2s infinite ease-in-out; animation-delay: 0.4s; }
.tornado-spin ellipse:nth-child(5) { animation: wobble 2s infinite ease-in-out; animation-delay: 0.5s; }
.tornado-spin ellipse:nth-child(6) { animation: wobble 2s infinite ease-in-out; animation-delay: 0.6s; }
.tornado-spin ellipse:nth-child(7) { animation: wobble 2s infinite ease-in-out; animation-delay: 0.7s; }
.tornado-spin ellipse:nth-child(8) { animation: wobble 2s infinite ease-in-out; animation-delay: 0.8s; }

.hero h1 {
  font-size: 2.5rem;
  font-weight: 800;
  margin-bottom: 20px;
  line-height: 1.2;
}

.hero p {
  font-size: 1.125rem;
  color: var(--text-light);
  margin-bottom: 40px;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

/* Section Titles */
.section-title {
  text-align: center;
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 50px;
}

/* Features Section */
.features {
  padding: 80px 0;
  background-color: var(--bg-color);
}

.features-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 30px;
}

.feature-card {
  background-color: var(--card-bg);
  padding: 40px 30px;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-sm);
  text-align: center;
  transition: var(--transition);
  border: 1px solid var(--border-color);
}

.feature-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-md);
}

.feature-icon {
  width: 64px;
  height: 64px;
  margin: 0 auto 20px;
  background: linear-gradient(135deg, rgba(0, 210, 255, 0.1), rgba(58, 123, 213, 0.1));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--secondary-color);
}

.feature-icon svg {
  width: 32px;
  height: 32px;
}

.feature-card h3 {
  font-size: 1.25rem;
  margin-bottom: 15px;
}

.feature-card p {
  color: var(--text-light);
  font-size: 0.95rem;
}

/* Pricing Section */
.pricing {
  padding: 80px 0;
  background-color: #ffffff;
}

.pricing-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 30px;
}

.pricing-card {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: 40px 30px;
  text-align: center;
  transition: var(--transition);
  position: relative;
}

.pricing-card.popular {
  border-color: var(--secondary-color);
  box-shadow: var(--shadow-lg);
  transform: scale(1.02);
}

.popular-badge {
  position: absolute;
  top: -15px;
  left: 50%;
  transform: translateX(-50%);
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: var(--text-white);
  padding: 5px 15px;
  border-radius: 20px;
  font-size: 0.85rem;
  font-weight: 600;
}

.pricing-card h3 {
  font-size: 1.5rem;
  margin-bottom: 15px;
}

.price {
  font-size: 3rem;
  font-weight: 800;
  color: var(--text-dark);
  margin-bottom: 20px;
  display: flex;
  justify-content: center;
  align-items: baseline;
}

.price span {
  font-size: 1rem;
  color: var(--text-light);
  font-weight: normal;
  margin-left: 5px;
}

.pricing-features {
  margin: 30px 0;
  text-align: left;
}

.pricing-features li {
  margin-bottom: 15px;
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text-light);
}

.pricing-features li svg {
  color: #10b981;
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}

/* FAQ Section */
.faq {
  padding: 80px 0;
  background-color: var(--bg-color);
}

.faq-list {
  max-width: 800px;
  margin: 0 auto;
}

details {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  margin-bottom: 15px;
  overflow: hidden;
}

summary {
  padding: 20px;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  list-style: none;
}

summary::-webkit-details-marker {
  display: none;
}

summary::after {
  content: '+';
  font-size: 1.5rem;
  color: var(--text-light);
  transition: transform 0.3s ease;
}

details[open] summary::after {
  content: '−';
}

details p {
  padding: 0 20px 20px;
  color: var(--text-light);
  border-top: 1px solid #f3f4f6;
  margin-top: -5px;
  padding-top: 20px;
}

/* Footer */
.footer {
  background-color: #111827;
  color: #9ca3af;
  padding: 60px 0 30px;
  text-align: center;
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 20px;
  margin-bottom: 30px;
}

.footer-links a {
  color: #d1d5db;
  transition: var(--transition);
}

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

.copyright {
  font-size: 0.9rem;
  border-top: 1px solid #374151;
  padding-top: 30px;
}

/* Auxiliary Pages Content */
.page-header {
  padding: 60px 0;
  text-align: center;
  background: linear-gradient(180deg, #f0f7ff 0%, #ffffff 100%);
  border-bottom: 1px solid var(--border-color);
}

.page-header h1 {
  font-size: 2rem;
  font-weight: 700;
}

.page-content {
  padding: 60px 0;
  background-color: var(--card-bg);
}

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

.content-wrapper h2 {
  font-size: 1.5rem;
  margin-top: 30px;
  margin-bottom: 15px;
  color: var(--text-dark);
}

.content-wrapper p {
  margin-bottom: 15px;
  color: var(--text-light);
  line-height: 1.8;
}

.content-wrapper ul {
  list-style: disc;
  padding-left: 20px;
  margin-bottom: 20px;
  color: var(--text-light);
}

.content-wrapper ul li {
  margin-bottom: 10px;
}

/* Responsive Media Queries */
@media (min-width: 768px) {
  .hero-content {
    flex-direction: row;
    text-align: left;
  }
  
  .hero p {
    margin-left: 0;
  }

  .hero h1 {
    font-size: 3.5rem;
  }
  
  .hero p {
    font-size: 1.25rem;
  }
  
  .features-grid {
    grid-template-columns: repeat(3, 1fr);
  }
  
  .pricing-grid {
    grid-template-columns: repeat(3, 1fr);
    align-items: center;
  }
}

/* Utilities added for SEO rebuild */
.btn-block { width: 100%; }
.btn-lg { padding: 15px 40px; font-size: 1.1rem; }
.cta-center { text-align: center; margin-top: 40px; }
.text-link { color: var(--secondary-color); text-decoration: underline; font-weight: 600; }
.text-link:hover { color: var(--primary-color); }

.breadcrumb { font-size: 0.9rem; color: var(--text-light); margin-bottom: 12px; }
.breadcrumb a { color: var(--secondary-color); }
.breadcrumb a:hover { text-decoration: underline; }
.page-meta { margin-top: 10px; font-size: 0.9rem; color: var(--text-light); }

/* Guide steps */
.guide { padding: 80px 0; background-color: #ffffff; }
.steps { list-style: none; display: grid; grid-template-columns: 1fr; gap: 30px; }
.step-card {
  background: var(--bg-color);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: 36px 28px 30px;
  text-align: center;
}
.step-num {
  display: inline-flex; align-items: center; justify-content: center;
  width: 44px; height: 44px; border-radius: 50%; margin-bottom: 16px;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: #fff; font-weight: 800; font-size: 1.2rem;
}
.step-card h3 { font-size: 1.2rem; margin-bottom: 10px; }
.step-card p { color: var(--text-light); font-size: 0.95rem; }
@media (min-width: 768px) { .steps { grid-template-columns: repeat(3, 1fr); } }

.friend-links { text-align: center; margin-top: 15px; font-size: 14px; color: #6b7280; }
.friend-links a { color: #9ca3af; margin: 0 8px; }
.friend-links a:hover { color: var(--primary-color); }

.navbar { gap: 16px; }
@media (max-width: 380px) { .logo { font-size: 1.25rem; } .navbar .btn { padding: 10px 18px; } }

@media (prefers-reduced-motion: reduce) {
  .tornado-svg, .tornado-spin ellipse { animation: none !important; }
}

/* Article components */
.summary-box {
  background: linear-gradient(135deg, rgba(0, 210, 255, 0.08), rgba(58, 123, 213, 0.08));
  border-left: 4px solid var(--secondary-color);
  border-radius: 8px;
  padding: 18px 20px 4px;
  margin-bottom: 28px;
}
.summary-box p { color: var(--text-dark); }
.content-wrapper h3 { font-size: 1.15rem; margin: 22px 0 10px; color: var(--text-dark); }
.content-wrapper ol { list-style: decimal; padding-left: 22px; margin-bottom: 20px; color: var(--text-light); }
.content-wrapper ol li { margin-bottom: 10px; }
.content-wrapper table { width: 100%; border-collapse: collapse; margin: 10px 0 24px; font-size: 0.95rem; display: block; overflow-x: auto; }
.content-wrapper th, .content-wrapper td { border: 1px solid var(--border-color); padding: 10px 12px; text-align: left; color: var(--text-light); white-space: nowrap; }
.content-wrapper th { background: var(--bg-color); color: var(--text-dark); font-weight: 700; }
@media (min-width: 768px) { .content-wrapper table { display: table; } .content-wrapper th, .content-wrapper td { white-space: normal; } }
.related { margin-top: 48px; padding-top: 24px; border-top: 1px solid var(--border-color); }
.related h2 { margin-top: 0; }
.related a { color: var(--secondary-color); font-weight: 600; }
.related a:hover { text-decoration: underline; }

/* Homepage article cards */
.articles { padding: 80px 0; background-color: #ffffff; }
.article-grid { display: grid; grid-template-columns: 1fr; gap: 20px; }
@media (min-width: 768px) { .article-grid { grid-template-columns: repeat(2, 1fr); } }
.article-card {
  display: block; padding: 26px 24px; border: 1px solid var(--border-color);
  border-radius: var(--border-radius); background: var(--bg-color); transition: var(--transition);
}
.article-card:hover { border-color: var(--secondary-color); box-shadow: var(--shadow-md); transform: translateY(-3px); }
.article-card h3 { font-size: 1.1rem; margin-bottom: 8px; color: var(--text-dark); }
.article-card p { color: var(--text-light); font-size: 0.95rem; }
.guide { background-color: var(--bg-color); }
.guide .step-card { background: #ffffff; }