* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
  background: #f5f5f5;
  color: #333;
  line-height: 1.6;
}

a {
  color: #007bff;
  text-decoration: none;
  transition: color 0.2s;
}

a:hover {
  color: #0056b3;
  text-decoration: underline;
}

.header {
  background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
  color: white;
  padding: 1rem 0;
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: 0 2px 8px rgba(0,0,0,0.15);
}

.header-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-size: 1.5rem;
  font-weight: bold;
  color: white;
  text-decoration: none;
  letter-spacing: 1px;
}

.logo:hover {
  color: #ecf0f1;
  text-decoration: none;
}

.nav {
  display: flex;
  flex-wrap: nowrap;
  gap: 1.5rem;
  align-items: center;
}

.nav a {
  color: white;
  white-space: nowrap;
  padding: 0.5rem 1rem;
  border-radius: 4px;
  transition: background 0.2s;
}

.nav a:hover {
  background: rgba(255,255,255,0.1);
  text-decoration: none;
}

.container {
  max-width: 1200px;
  margin: 2rem auto;
  padding: 0 1rem;
}

.section {
  background: white;
  border-radius: 8px;
  padding: 2rem;
  margin-bottom: 2rem;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}

.section-title {
  font-size: 1.8rem;
  font-weight: bold;
  margin-bottom: 1rem;
  color: #2c3e50;
  border-left: 4px solid #007bff;
  padding-left: 1rem;
}

.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.5rem;
  margin-top: 1.5rem;
}

.video-card {
  background: white;
  border-radius: 8px;
  padding: 1.5rem;
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
  transition: transform 0.2s, box-shadow 0.2s;
  border: 1px solid #e9ecef;
}

.video-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 4px 16px rgba(0,0,0,0.12);
}

.video-title {
  font-size: 1.2rem;
  font-weight: bold;
  margin-bottom: 0.5rem;
  color: #2c3e50;
}

.video-title a {
  color: #2c3e50;
}

.video-title a:hover {
  color: #007bff;
}

.video-meta {
  font-size: 0.9rem;
  color: #6c757d;
  margin-bottom: 0.75rem;
}

.video-desc {
  font-size: 0.95rem;
  color: #555;
  line-height: 1.6;
}

.footer {
  background: linear-gradient(135deg, #2c3e50 0%, #34495e 100%);
  color: white;
  text-align: center;
  padding: 2rem 0;
  margin-top: 3rem;
}

@media (max-width: 768px) {
  .header-content {
    flex-direction: column;
    gap: 1rem;
  }

  .nav {
    width: 100%;
    justify-content: space-between;
    gap: 0;
    flex-wrap: nowrap;
    overflow: hidden;
  }

  .nav a {
    flex: 1 1 0;
    min-width: 0;
    text-align: center;
    font-size: 0.85rem;
    padding: 0.5rem 0.25rem;
    overflow: hidden;
    text-overflow: ellipsis;
  }

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

  .section {
    padding: 1.5rem;
  }

  .section-title {
    font-size: 1.5rem;
  }
}

@media (max-width: 480px) {
  .nav a {
    font-size: 0.75rem;
    padding: 0.4rem 0.2rem;
  }
}