:root {
  --primary-color: #0066cc;
  --secondary-color: #004499;
  --text-color: #333;
  --light-bg: #f5f5f5;
  --border-color: #e0e0e0;
  --card-bg: #ffffff;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

main {
  flex: 1;
  padding: 2rem 0;
}

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

.hero {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: 3rem 0;
  text-align: center;
}

.hero h1 {
  font-size: 2rem;
  margin-bottom: 1rem;
  line-height: 1.4;
}

.hero .intro {
  font-size: 1.1rem;
  opacity: 0.95;
  max-width: 800px;
  margin: 0 auto;
}

section {
  margin-bottom: 3rem;
}

section h2 {
  font-size: 1.75rem;
  margin-bottom: 1.5rem;
  color: var(--text-color);
  border-left: 4px solid var(--primary-color);
  padding-left: 1rem;
}

.site-intro {
  background: var(--card-bg);
  padding: 2rem 0;
}

.site-intro p {
  line-height: 1.8;
  font-size: 1rem;
  color: #555;
}

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

.video-card {
  background: var(--card-bg);
  border-radius: 8px;
  padding: 1.5rem;
  box-shadow: var(--shadow);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.video-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
}

.video-card h3 {
  font-size: 1.1rem;
  margin-bottom: 0.75rem;
  line-height: 1.4;
}

.video-card h3 a {
  color: var(--text-color);
}

.video-card h3 a:hover {
  color: var(--primary-color);
}

.video-card .meta {
  font-size: 0.875rem;
  color: #666;
  margin-bottom: 0.5rem;
}

.video-card .one-line {
  font-size: 0.9rem;
  color: #555;
  line-height: 1.5;
}

.video-card .tags {
  font-size: 0.85rem;
  color: #888;
  margin-top: 0.5rem;
}

.video-card .summary {
  font-size: 0.875rem;
  color: #666;
  line-height: 1.6;
  margin-top: 0.5rem;
}

.video-card.full {
  padding: 2rem;
}

.video-card .card-header {
  margin-bottom: 1rem;
}

.video-card .category {
  display: inline-block;
  background: #f0f0f0;
  padding: 0.25rem 0.75rem;
  border-radius: 4px;
  font-size: 0.8rem;
  color: #666;
}

.video-card.topic .topic-badge {
  display: inline-block;
  background: var(--primary-color);
  color: white;
  padding: 0.25rem 0.75rem;
  border-radius: 4px;
  font-size: 0.8rem;
  margin-bottom: 0.75rem;
}

.video-card.latest .date-badge {
  display: inline-block;
  background: #ff6b6b;
  color: white;
  padding: 0.25rem 0.75rem;
  border-radius: 4px;
  font-size: 0.8rem;
  margin-bottom: 0.75rem;
}

.video-list {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.list-item {
  background: var(--card-bg);
  border-radius: 8px;
  padding: 1.5rem;
  box-shadow: var(--shadow);
  display: flex;
  gap: 1rem;
  align-items: flex-start;
  transition: transform 0.3s ease;
}

.list-item:hover {
  transform: translateX(4px);
}

.list-item .rank {
  font-size: 1.5rem;
  font-weight: bold;
  color: #999;
  min-width: 40px;
  text-align: center;
}

.list-item.ranked .rank-badge {
  font-size: 1.25rem;
  font-weight: bold;
  min-width: 40px;
  text-align: center;
  color: #999;
}

.list-item.ranked .rank-badge.top-three {
  color: #ff6b6b;
}

.list-item .item-content {
  flex: 1;
}

.list-item h3 {
  font-size: 1.1rem;
  margin-bottom: 0.5rem;
}

.list-item h3 a {
  color: var(--text-color);
}

.list-item h3 a:hover {
  color: var(--primary-color);
}

.list-item .meta {
  font-size: 0.875rem;
  color: #666;
  margin-bottom: 0.25rem;
}

.list-item .one-line {
  font-size: 0.9rem;
  color: #555;
  line-height: 1.5;
}

.more-link {
  text-align: center;
  margin-top: 2rem;
}

.more-link a {
  display: inline-block;
  padding: 0.75rem 2rem;
  background: var(--primary-color);
  color: white;
  border-radius: 4px;
  font-weight: 500;
  transition: background 0.3s ease;
}

.more-link a:hover {
  background: var(--secondary-color);
}

.page-header {
  background: var(--card-bg);
  padding: 2rem 0;
  margin-bottom: 2rem;
  border-bottom: 2px solid var(--border-color);
}

.page-header h1 {
  font-size: 2rem;
  margin-bottom: 0.75rem;
  color: var(--text-color);
}

.page-intro {
  font-size: 1rem;
  line-height: 1.7;
  color: #555;
  max-width: 900px;
}

.detail-page {
  background: var(--card-bg);
  border-radius: 8px;
  padding: 2rem;
  box-shadow: var(--shadow);
}

.detail-header {
  border-bottom: 2px solid var(--border-color);
  padding-bottom: 1.5rem;
  margin-bottom: 2rem;
}

.detail-header h1 {
  font-size: 2.25rem;
  margin-bottom: 0.5rem;
  color: var(--text-color);
}

.detail-header .subtitle {
  font-size: 1rem;
  color: #666;
}

.detail-page section {
  margin-bottom: 2rem;
}

.detail-page h2 {
  font-size: 1.5rem;
  margin-bottom: 1rem;
  color: var(--text-color);
  border-left: 4px solid var(--primary-color);
  padding-left: 1rem;
}

.info-list {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.75rem 1rem;
  font-size: 1rem;
  line-height: 1.6;
}

.info-list dt {
  font-weight: 600;
  color: #555;
}

.info-list dd {
  color: #333;
}

.highlight {
  font-size: 1.1rem;
  line-height: 1.7;
  color: var(--primary-color);
  font-weight: 500;
  background: #f8f9fa;
  padding: 1rem;
  border-left: 4px solid var(--primary-color);
  border-radius: 4px;
}

.detail-summary p,
.detail-review p {
  font-size: 1rem;
  line-height: 1.8;
  color: #333;
}

footer {
  background: #2c3e50;
  color: white;
  padding: 2rem 0;
  margin-top: auto;
  text-align: center;
}

footer p {
  font-size: 0.9rem;
  opacity: 0.9;
}

@media (max-width: 768px) {
  .hero h1 {
    font-size: 1.5rem;
  }

  .hero .intro {
    font-size: 1rem;
  }

  section h2 {
    font-size: 1.5rem;
  }

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

  .detail-header h1 {
    font-size: 1.75rem;
  }

  .info-list {
    grid-template-columns: 1fr;
    gap: 0.5rem;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 0.75rem;
  }

  .hero {
    padding: 2rem 0;
  }

  main {
    padding: 1rem 0;
  }

  .video-card,
  .list-item {
    padding: 1rem;
  }
}