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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  line-height: 1.6;
  color: #333;
  background: #f5f5f5;
}

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

header {
  background: #fff;
  box-shadow: 0 2px 4px rgba(0,0,0,0.1);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 15px 20px;
}

.logo {
  font-size: 24px;
  font-weight: bold;
  color: #2c3e50;
  text-decoration: none;
}

nav ul {
  display: flex;
  list-style: none;
  gap: 30px;
  flex-wrap: nowrap;
}

nav a {
  color: #555;
  text-decoration: none;
  transition: color 0.3s;
  white-space: nowrap;
}

nav a:hover {
  color: #3498db;
}

main {
  padding: 40px 0;
}

h1 {
  font-size: 32px;
  margin-bottom: 20px;
  color: #2c3e50;
  line-height: 1.3;
}

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

.intro {
  background: #fff;
  padding: 30px;
  border-radius: 8px;
  margin-bottom: 40px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 24px;
  margin-bottom: 40px;
}

.video-card {
  background: #fff;
  border-radius: 8px;
  padding: 20px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.05);
  transition: transform 0.3s, box-shadow 0.3s;
}

.video-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 4px 16px rgba(0,0,0,0.1);
}

.video-card h3 {
  font-size: 18px;
  margin-bottom: 10px;
  color: #2c3e50;
}

.video-card .meta {
  font-size: 14px;
  color: #7f8c8d;
  margin-bottom: 10px;
}

.video-card .desc {
  font-size: 14px;
  color: #666;
  line-height: 1.5;
  margin-bottom: 15px;
}

.video-card a {
  display: inline-block;
  padding: 8px 16px;
  background: #3498db;
  color: #fff;
  text-decoration: none;
  border-radius: 4px;
  font-size: 14px;
  transition: background 0.3s;
}

.video-card a:hover {
  background: #2980b9;
}

.detail-content {
  background: #fff;
  padding: 40px;
  border-radius: 8px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.05);
  margin-bottom: 40px;
}

.detail-meta {
  background: #f8f9fa;
  padding: 20px;
  border-radius: 6px;
  margin: 20px 0;
}

.detail-meta p {
  margin: 8px 0;
  font-size: 15px;
}

.detail-meta strong {
  color: #2c3e50;
  display: inline-block;
  min-width: 80px;
}

.section {
  margin: 30px 0;
}

.section h2 {
  font-size: 22px;
  margin-bottom: 15px;
  padding-bottom: 10px;
  border-bottom: 2px solid #3498db;
}

.related-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 20px;
  margin-top: 20px;
}

.related-item {
  background: #f8f9fa;
  padding: 15px;
  border-radius: 6px;
  transition: background 0.3s;
}

.related-item:hover {
  background: #e9ecef;
}

.related-item h4 {
  font-size: 16px;
  margin-bottom: 8px;
  color: #2c3e50;
}

.related-item p {
  font-size: 13px;
  color: #666;
  margin-bottom: 10px;
}

.related-item a {
  color: #3498db;
  text-decoration: none;
  font-size: 14px;
}

footer {
  background: #2c3e50;
  color: #ecf0f1;
  text-align: center;
  padding: 20px 0;
  margin-top: 60px;
}

@media (max-width: 768px) {
  .header-content {
    flex-direction: column;
    gap: 15px;
  }

  nav ul {
    width: 100%;
    justify-content: space-between;
    gap: 0;
    padding: 0;
  }

  nav li {
    flex: 1 1 0;
    min-width: 0;
    text-align: center;
  }

  nav a {
    display: block;
    padding: 8px 4px;
    font-size: 13px;
    overflow: hidden;
    text-overflow: ellipsis;
  }

  .logo {
    font-size: 20px;
  }

  h1 {
    font-size: 24px;
  }

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

  .detail-content {
    padding: 20px;
  }
}