:root {
  --primary-color: #3498db;
  --secondary-color: #2c3e50;
  --accent-color: #e74c3c;
  --bg-color: #f5f5f5;
  --card-bg: #ffffff;
  --text-color: #333;
  --border-color: #ddd;
  --shadow: 0 2px 8px rgba(0,0,0,0.1);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
  background: var(--bg-color);
  color: var(--text-color);
  line-height: 1.7;
}

header {
  background: var(--secondary-color);
  color: white;
  padding: 1.5rem 1rem;
  box-shadow: var(--shadow);
  position: sticky;
  top: 0;
  z-index: 1000;
}

header nav {
  max-width: 1200px;
  margin: 0 auto;
}

header h2 {
  margin-bottom: 0.75rem;
  font-size: 1.5rem;
}

header ul {
  list-style: none;
  display: flex;
  flex-wrap: nowrap;
  justify-content: space-between;
  align-items: center;
  gap: 0.75rem;
}

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

header a {
  color: white;
  text-decoration: none;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  display: block;
  padding: 0.6rem 0.5rem;
  border-radius: 4px;
  transition: background-color 0.3s, opacity 0.3s;
}

header a:hover {
  background-color: rgba(255,255,255,0.1);
  opacity: 0.9;
}

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

h1 {
  font-size: 2rem;
  margin-bottom: 1.5rem;
  color: var(--secondary-color);
  border-left: 4px solid var(--primary-color);
  padding-left: 1rem;
}

h2 {
  font-size: 1.5rem;
  margin: 2rem 0 1rem;
  color: var(--secondary-color);
}

h3 {
  font-size: 1.2rem;
  margin: 1rem 0 0.5rem;
}

.intro, .site-intro {
  background: var(--card-bg);
  padding: 1.5rem;
  border-radius: 8px;
  margin-bottom: 2rem;
  box-shadow: var(--shadow);
  line-height: 1.8;
}

.intro a, .site-intro a {
  color: var(--primary-color);
  text-decoration: none;
  border-bottom: 1px solid var(--primary-color);
}

.intro a:hover, .site-intro a:hover {
  opacity: 0.8;
}

.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2rem;
}

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

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

.video-card h3 a {
  color: var(--secondary-color);
  text-decoration: none;
  font-size: 1.1rem;
}

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

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

.video-card .intro {
  margin: 0;
  padding: 0;
  background: none;
  box-shadow: none;
  font-size: 0.95rem;
  color: #555;
  line-height: 1.6;
}

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

.video-item {
  background: var(--card-bg);
  padding: 1.25rem;
  border-radius: 8px;
  box-shadow: var(--shadow);
  transition: box-shadow 0.3s;
}

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

.video-item h3 {
  margin-top: 0;
}

.video-item h3 a {
  color: var(--secondary-color);
  text-decoration: none;
}

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

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

.video-item p {
  color: #555;
  margin: 0.5rem 0 0;
}

.entrance-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.entrance-card {
  background: var(--card-bg);
  padding: 2rem;
  border-radius: 8px;
  box-shadow: var(--shadow);
  transition: transform 0.3s, box-shadow 0.3s;
  text-align: center;
}

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

.entrance-card h3 a {
  color: var(--primary-color);
  text-decoration: none;
  font-size: 1.3rem;
}

.entrance-card p {
  color: #666;
  margin-top: 0.75rem;
  line-height: 1.6;
}

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

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

.detail-page .basic-info ul {
  list-style: none;
  padding: 0;
}

.detail-page .basic-info li {
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--border-color);
}

.detail-page .basic-info li:last-child {
  border-bottom: none;
}

.related-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}

.related-item {
  background: var(--bg-color);
  padding: 1rem;
  border-radius: 6px;
  border: 1px solid var(--border-color);
}

.related-item h3 {
  font-size: 1rem;
  margin-top: 0;
}

.related-item h3 a {
  color: var(--secondary-color);
  text-decoration: none;
}

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

.related-item p {
  font-size: 0.9rem;
  color: #666;
  margin: 0.5rem 0 0;
}

.year-group {
  margin-bottom: 2.5rem;
}

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

.video-item-simple {
  background: var(--card-bg);
  padding: 1rem;
  border-radius: 6px;
  border: 1px solid var(--border-color);
}

.video-item-simple h3 {
  font-size: 1rem;
  margin: 0 0 0.5rem;
}

.video-item-simple h3 a {
  color: var(--secondary-color);
  text-decoration: none;
}

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

.video-item-simple .meta {
  font-size: 0.85rem;
  color: #666;
  margin-bottom: 0.5rem;
}

.video-item-simple .desc {
  font-size: 0.9rem;
  color: #555;
  margin: 0;
}

.top-list {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.top-item {
  background: var(--card-bg);
  padding: 1.5rem;
  border-radius: 8px;
  box-shadow: var(--shadow);
  display: flex;
  gap: 1.5rem;
  align-items: flex-start;
}

.rank-num {
  font-size: 2rem;
  font-weight: bold;
  color: var(--primary-color);
  min-width: 50px;
  text-align: center;
  background: var(--bg-color);
  padding: 0.5rem;
  border-radius: 6px;
}

.top-content {
  flex: 1;
}

.top-content h2 {
  margin: 0 0 0.5rem;
  font-size: 1.3rem;
}

.top-content h2 a {
  color: var(--secondary-color);
  text-decoration: none;
}

.top-content h2 a:hover {
  color: var(--primary-color);
}

.top-content .meta,
.top-content .tags {
  font-size: 0.9rem;
  color: #666;
  margin: 0.3rem 0;
}

.top-content .recommend {
  margin-top: 0.75rem;
  color: #555;
  line-height: 1.7;
}

.topic-intro {
  padding: 2rem;
  font-size: 1rem;
  line-height: 1.9;
}

.topic-list {
  display: flex;
  flex-direction: column;
  gap: 2rem;
}

.topic-item {
  background: var(--card-bg);
  padding: 1.75rem;
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.topic-item h2 {
  margin: 0 0 0.5rem;
  font-size: 1.3rem;
}

.topic-item h2 a {
  color: var(--secondary-color);
  text-decoration: none;
}

.topic-item h2 a:hover {
  color: var(--primary-color);
}

.topic-item .meta {
  font-size: 0.9rem;
  color: #666;
  margin-bottom: 1rem;
}

.topic-desc p {
  margin-bottom: 0.75rem;
  color: #555;
  line-height: 1.8;
}

.topic-desc .why-in-topic {
  color: #666;
  font-style: italic;
  border-left: 3px solid var(--primary-color);
  padding-left: 1rem;
  margin-top: 1rem;
}

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

.latest-item {
  background: var(--card-bg);
  padding: 1.25rem;
  border-radius: 8px;
  box-shadow: var(--shadow);
  display: flex;
  gap: 1.25rem;
  align-items: flex-start;
}

.date-badge {
  background: var(--primary-color);
  color: white;
  padding: 0.5rem 0.75rem;
  border-radius: 6px;
  font-size: 0.85rem;
  font-weight: bold;
  white-space: nowrap;
  min-width: 100px;
  text-align: center;
}

.latest-content {
  flex: 1;
}

.latest-content h2 {
  margin: 0 0 0.5rem;
  font-size: 1.2rem;
}

.latest-content h2 a {
  color: var(--secondary-color);
  text-decoration: none;
}

.latest-content h2 a:hover {
  color: var(--primary-color);
}

.latest-content .meta {
  font-size: 0.85rem;
  color: #666;
  margin-bottom: 0.5rem;
}

.latest-content .brief {
  color: #555;
  font-size: 0.95rem;
  margin: 0;
}

footer {
  background: var(--secondary-color);
  color: white;
  padding: 2rem 1rem;
  margin-top: 3rem;
  text-align: center;
}

footer nav {
  margin-bottom: 1rem;
}

footer a {
  color: white;
  text-decoration: none;
  margin: 0 1rem;
  transition: opacity 0.3s;
}

footer a:hover {
  opacity: 0.8;
}

@media (max-width: 768px) {
  header h2 {
    font-size: 1.2rem;
  }

  header ul {
    gap: 0.4rem;
  }

  header a {
    font-size: 0.85rem;
    padding: 0.5rem 0.3rem;
  }

  h1 {
    font-size: 1.5rem;
  }

  h2 {
    font-size: 1.3rem;
  }

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

  .top-item {
    flex-direction: column;
    align-items: center;
    text-align: center;
  }

  .latest-item {
    flex-direction: column;
    align-items: stretch;
  }

  .date-badge {
    align-self: flex-start;
  }

  footer a {
    display: block;
    margin: 0.5rem 0;
  }
}

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

  main {
    padding: 0 0.75rem;
  }

  .intro, .site-intro, .detail-page .video-detail {
    padding: 1rem;
  }
}