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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  line-height: 1.6;
  color: #2c3e50;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  background-attachment: fixed;
  min-height: 100vh;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
}

header {
  background: rgba(255, 255, 255, 0.98);
  box-shadow: 0 2px 15px rgba(0, 0, 0, 0.1);
  position: sticky;
  top: 0;
  z-index: 1000;
  backdrop-filter: blur(10px);
}

.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 15px 0;
}

.logo {
  font-size: 26px;
  font-weight: 700;
  color: #667eea;
  text-decoration: none;
  letter-spacing: 1px;
  transition: color 0.3s ease;
}

.logo:hover {
  color: #764ba2;
}

nav ul {
  list-style: none;
  display: flex;
  flex-wrap: nowrap;
  gap: 8px;
  align-items: center;
}

nav ul li a {
  color: #34495e;
  text-decoration: none;
  padding: 10px 16px;
  border-radius: 6px;
  transition: all 0.3s ease;
  font-weight: 500;
  white-space: nowrap;
  display: block;
}

nav ul li a:hover {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  transform: translateY(-2px);
}

main {
  background: white;
  margin: 30px auto;
  padding: 40px;
  border-radius: 15px;
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.15);
  min-height: 500px;
}

h1 {
  font-size: 32px;
  color: #2c3e50;
  margin-bottom: 25px;
  padding-bottom: 15px;
  border-bottom: 3px solid #667eea;
  line-height: 1.3;
}

h2 {
  font-size: 24px;
  color: #34495e;
  margin: 30px 0 20px;
  line-height: 1.3;
}

h3 {
  font-size: 20px;
  color: #34495e;
  margin: 25px 0 15px;
  line-height: 1.3;
}

.intro-section {
  background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
  padding: 30px;
  border-radius: 10px;
  margin-bottom: 40px;
  line-height: 1.8;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.08);
}

.content-section {
  margin-bottom: 50px;
}

.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 25px;
  margin-top: 25px;
}

.video-card {
  background: white;
  border: 1px solid #e1e8ed;
  border-radius: 10px;
  padding: 20px;
  transition: all 0.3s ease;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05);
}

.video-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 25px rgba(102, 126, 234, 0.3);
  border-color: #667eea;
}

.video-card h3 {
  margin: 0 0 12px 0;
  font-size: 18px;
}

.video-card h3 a {
  color: #2c3e50;
  text-decoration: none;
  transition: color 0.3s ease;
}

.video-card h3 a:hover {
  color: #667eea;
}

.video-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 12px;
  font-size: 13px;
  color: #7f8c8d;
}

.video-meta span {
  background: #ecf0f1;
  padding: 3px 10px;
  border-radius: 4px;
}

.video-desc {
  color: #555;
  font-size: 14px;
  line-height: 1.6;
  margin-bottom: 12px;
}

.video-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 10px;
}

.tag {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: 4px 10px;
  border-radius: 15px;
  font-size: 12px;
  text-decoration: none;
  transition: transform 0.2s ease;
}

.tag:hover {
  transform: scale(1.05);
}

.video-list {
  list-style: none;
  padding: 0;
}

.video-list-item {
  background: #f8f9fa;
  margin-bottom: 20px;
  padding: 25px;
  border-radius: 10px;
  border-left: 4px solid #667eea;
  transition: all 0.3s ease;
}

.video-list-item:hover {
  background: #fff;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
  transform: translateX(5px);
}

.video-list-item h3 {
  margin: 0 0 12px 0;
}

.video-list-item h3 a {
  color: #2c3e50;
  text-decoration: none;
  font-size: 20px;
}

.video-list-item h3 a:hover {
  color: #667eea;
}

.detail-meta {
  background: #f8f9fa;
  padding: 25px;
  border-radius: 10px;
  margin: 30px 0;
}

.detail-meta dl {
  display: grid;
  grid-template-columns: 120px 1fr;
  gap: 15px;
  margin: 0;
}

.detail-meta dt {
  font-weight: 600;
  color: #34495e;
}

.detail-meta dd {
  margin: 0;
  color: #555;
}

.summary-box {
  background: linear-gradient(135deg, #fff5f5 0%, #ffeef0 100%);
  padding: 25px;
  border-radius: 10px;
  margin: 25px 0;
  border-left: 4px solid #764ba2;
  line-height: 1.8;
}

.review-box {
  background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
  padding: 25px;
  border-radius: 10px;
  margin: 25px 0;
  border-left: 4px solid #667eea;
  line-height: 1.8;
}

.related-section {
  margin-top: 50px;
  padding-top: 30px;
  border-top: 2px solid #e1e8ed;
}

.rank-number {
  display: inline-block;
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  text-align: center;
  line-height: 36px;
  border-radius: 50%;
  font-weight: 700;
  margin-right: 12px;
  font-size: 16px;
}

.date-badge {
  display: inline-block;
  background: #e74c3c;
  color: white;
  padding: 4px 12px;
  border-radius: 4px;
  font-size: 13px;
  margin-right: 12px;
  font-weight: 500;
}

.group-section {
  margin-bottom: 45px;
}

.group-section h2 {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: 12px 20px;
  border-radius: 8px;
  margin-bottom: 20px;
}

.quick-links {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 20px;
  margin: 30px 0;
}

.quick-link-card {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: 30px;
  border-radius: 10px;
  text-align: center;
  text-decoration: none;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(102, 126, 234, 0.3);
}

.quick-link-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 25px rgba(102, 126, 234, 0.5);
}

.quick-link-card h3 {
  color: white;
  margin: 0 0 10px 0;
}

.quick-link-card p {
  color: rgba(255, 255, 255, 0.9);
  font-size: 14px;
  margin: 0;
}

footer {
  background: rgba(255, 255, 255, 0.95);
  padding: 30px 0;
  margin-top: 50px;
  border-top: 1px solid #e1e8ed;
}

.footer-content {
  text-align: center;
}

.footer-nav {
  list-style: none;
  display: flex;
  justify-content: center;
  flex-wrap: nowrap;
  gap: 8px;
  margin-bottom: 15px;
}

.footer-nav li a {
  color: #34495e;
  text-decoration: none;
  padding: 8px 14px;
  border-radius: 4px;
  transition: all 0.3s ease;
  white-space: nowrap;
  display: block;
}

.footer-nav li a:hover {
  color: #667eea;
  background: #f5f7fa;
}

.copyright {
  color: #7f8c8d;
  font-size: 14px;
}

.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  width: 50px;
  height: 50px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
  z-index: 999;
}

.back-to-top.visible {
  opacity: 1;
}

.back-to-top:hover {
  transform: translateY(-5px);
  box-shadow: 0 6px 20px rgba(102, 126, 234, 0.6);
}

@media (max-width: 768px) {
  body {
    font-size: 15px;
  }

  .header-content {
    flex-direction: column;
    gap: 12px;
    padding: 12px 0;
  }

  .logo {
    font-size: 22px;
  }

  nav ul {
    width: 100%;
    justify-content: space-between;
    gap: 4px;
    flex-wrap: nowrap;
  }

  nav ul li {
    flex: 1 1 0;
    min-width: 0;
  }

  nav ul li a {
    padding: 8px 6px;
    font-size: 13px;
    text-align: center;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
  }

  main {
    padding: 25px 20px;
    margin: 20px auto;
  }

  h1 {
    font-size: 24px;
  }

  h2 {
    font-size: 20px;
  }

  h3 {
    font-size: 18px;
  }

  .video-grid {
    grid-template-columns: 1fr;
    gap: 20px;
  }

  .detail-meta dl {
    grid-template-columns: 100px 1fr;
    gap: 10px;
  }

  .quick-links {
    grid-template-columns: 1fr;
  }

  .footer-nav {
    flex-wrap: nowrap;
    gap: 4px;
  }

  .footer-nav li {
    flex: 1 1 0;
    min-width: 0;
  }

  .footer-nav li a {
    padding: 8px 4px;
    font-size: 13px;
    text-align: center;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
  }

  .back-to-top {
    bottom: 20px;
    right: 20px;
    width: 45px;
    height: 45px;
  }
}

@media (max-width: 480px) {
  nav ul li a {
    font-size: 12px;
    padding: 8px 4px;
  }

  .footer-nav li a {
    font-size: 12px;
    padding: 6px 2px;
  }
}