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

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  line-height: 1.6;
  color: #333;
  background: #f5f5f5;
}

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

header {
  background: linear-gradient(135deg, #1e3c72 0%, #2a5298 100%);
  color: white;
  padding: 1rem 0;
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.logo {
  font-size: 1.8rem;
  font-weight: bold;
  color: white;
  text-decoration: none;
  display: inline-block;
  margin-bottom: 0.5rem;
}

nav {
  display: flex;
  flex-wrap: nowrap;
  justify-content: space-between;
  align-items: center;
  gap: 0.5rem;
}

nav a {
  color: white;
  text-decoration: none;
  padding: 0.5rem 1rem;
  border-radius: 4px;
  transition: background 0.3s;
  flex: 1 1 0;
  min-width: 0;
  text-align: center;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  font-size: 0.95rem;
}

nav a:hover {
  background: rgba(255,255,255,0.2);
}

@media (max-width: 768px) {
  nav {
    flex-wrap: nowrap;
    overflow-x: visible;
  }
  nav a {
    padding: 0.4rem 0.5rem;
    font-size: 0.85rem;
  }
}

main {
  padding: 2rem 0;
  min-height: calc(100vh - 200px);
}

h1 {
  font-size: 2rem;
  margin-bottom: 1rem;
  color: #1e3c72;
}

h2 {
  font-size: 1.5rem;
  margin: 2rem 0 1rem;
  color: #2a5298;
}

section {
  background: white;
  padding: 2rem;
  margin-bottom: 2rem;
  border-radius: 8px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.1);
}

.intro {
  font-size: 1.1rem;
  line-height: 1.8;
  color: #555;
}

.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.5rem;
  margin-top: 1.5rem;
}

.video-card {
  background: white;
  border-radius: 8px;
  padding: 1.5rem;
  transition: transform 0.3s, box-shadow 0.3s;
  border: 1px solid #e0e0e0;
}

.video-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 5px 20px rgba(0,0,0,0.15);
}

.video-card h3 {
  font-size: 1.2rem;
  margin-bottom: 0.5rem;
  color: #1e3c72;
}

.video-card a {
  color: #1e3c72;
  text-decoration: none;
  font-weight: bold;
}

.video-card a:hover {
  color: #2a5298;
  text-decoration: underline;
}

.video-meta {
  color: #666;
  font-size: 0.9rem;
  margin: 0.5rem 0;
}

.video-desc {
  color: #555;
  line-height: 1.6;
  margin-top: 0.5rem;
}

.detail-info {
  background: #f9f9f9;
  padding: 1.5rem;
  border-radius: 6px;
  margin-bottom: 2rem;
}

.detail-info p {
  margin: 0.5rem 0;
}

.detail-info strong {
  color: #1e3c72;
  min-width: 80px;
  display: inline-block;
}

.tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.5rem;
}

.tag {
  background: #e3f2fd;
  color: #1e3c72;
  padding: 0.25rem 0.75rem;
  border-radius: 4px;
  font-size: 0.85rem;
}

footer {
  background: #1e3c72;
  color: white;
  text-align: center;
  padding: 2rem 0;
  margin-top: 3rem;
}

.rank-number {
  display: inline-block;
  background: #1e3c72;
  color: white;
  width: 30px;
  height: 30px;
  line-height: 30px;
  text-align: center;
  border-radius: 50%;
  margin-right: 0.5rem;
  font-weight: bold;
}