:root {
  --primary-color: #667eea;
  --secondary-color: #764ba2;
  --text-color: #333;
  --text-light: #666;
  --bg-color: #f5f5f5;
  --card-bg: #fff;
  --border-color: #e0e0e0;
  --hover-color: #f0f0f0;
  --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  --shadow-hover: 0 4px 16px rgba(0, 0, 0, 0.15);
  --radius: 8px;
  --spacing: 1rem;
}

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

.main-content {
  flex: 1;
  padding: 2rem 0;
}

.hero-section {
  text-align: center;
  padding: 3rem 0;
  background: linear-gradient(135deg, rgba(102, 126, 234, 0.1) 0%, rgba(118, 75, 162, 0.1) 100%);
  border-radius: var(--radius);
  margin-bottom: 3rem;
}

.page-title {
  font-size: 2rem;
  color: var(--text-color);
  margin-bottom: 1rem;
  line-height: 1.4;
}

.intro-text,
.page-intro {
  font-size: 1.1rem;
  color: var(--text-light);
  line-height: 1.8;
  max-width: 900px;
  margin: 0 auto;
}

.section-title {
  font-size: 1.5rem;
  margin-bottom: 1.5rem;
  padding-bottom: 0.5rem;
  border-bottom: 3px solid var(--primary-color);
  display: inline-block;
}

.featured-section,
.ranking-section,
.latest-section {
  margin-bottom: 3rem;
}

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

.video-grid.large {
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 2rem;
}

.video-card {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow);
  transition: all 0.3s ease;
  position: relative;
}

.video-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-hover);
}

.rank-badge {
  position: absolute;
  top: -10px;
  right: -10px;
  width: 40px;
  height: 40px;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: bold;
  font-size: 1.1rem;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
}

.video-title {
  font-size: 1.2rem;
  margin-bottom: 0.8rem;
  color: var(--text-color);
}

.video-title a {
  color: inherit;
  transition: color 0.3s;
}

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

.video-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.8rem;
  margin-bottom: 1rem;
  font-size: 0.9rem;
  color: var(--text-light);
}

.meta-item {
  padding: 0.3rem 0.8rem;
  background: var(--hover-color);
  border-radius: 4px;
}

.video-desc {
  color: var(--text-light);
  line-height: 1.6;
  font-size: 0.95rem;
}

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

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

.ranking-item {
  display: flex;
  gap: 1.5rem;
  background: var(--card-bg);
  padding: 1.5rem;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  transition: all 0.3s ease;
}

.ranking-item:hover {
  transform: translateX(4px);
  box-shadow: var(--shadow-hover);
}

.rank-number {
  flex-shrink: 0;
  width: 50px;
  height: 50px;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: #fff;
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  font-weight: bold;
}

.ranking-content {
  flex: 1;
}

.topic-container {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 2rem;
}

.topic-card {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow);
  transition: all 0.3s ease;
}

.topic-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-hover);
}

.topic-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.topic-tag {
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: #fff;
  padding: 0.4rem 1rem;
  border-radius: 20px;
  font-size: 0.9rem;
}

.topic-year {
  color: var(--text-light);
  font-size: 0.9rem;
}

.topic-desc {
  color: var(--text-light);
  line-height: 1.6;
  margin-bottom: 1rem;
}

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.tag {
  padding: 0.3rem 0.8rem;
  background: var(--hover-color);
  border-radius: 4px;
  font-size: 0.85rem;
  color: var(--text-light);
}

.latest-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 2rem;
}

.latest-card {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 1.5rem;
  box-shadow: var(--shadow);
  transition: all 0.3s ease;
  position: relative;
}

.latest-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-hover);
}

.latest-badge {
  position: absolute;
  top: -10px;
  left: 1rem;
  background: #ff6b6b;
  color: #fff;
  padding: 0.4rem 1rem;
  border-radius: 20px;
  font-size: 0.85rem;
  font-weight: bold;
}

.review-snippet {
  margin-top: 1rem;
  padding: 1rem;
  background: var(--hover-color);
  border-left: 4px solid var(--primary-color);
  font-style: italic;
  color: var(--text-light);
  font-size: 0.9rem;
}

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

.btn-more {
  display: inline-block;
  padding: 0.8rem 2rem;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: #fff;
  border-radius: 25px;
  font-weight: 500;
  transition: all 0.3s ease;
  margin: 0 0.5rem;
}

.btn-more:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.4);
}

.detail-page {
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 2.5rem;
  box-shadow: var(--shadow);
}

.detail-title {
  font-size: 2rem;
  margin-bottom: 2rem;
  padding-bottom: 1rem;
  border-bottom: 3px solid var(--primary-color);
}

.detail-section {
  margin-bottom: 2.5rem;
}

.detail-info {
  margin-bottom: 2.5rem;
}

.info-list {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 1rem;
  line-height: 1.8;
}

.info-list dt {
  font-weight: 600;
  color: var(--text-color);
}

.info-list dd {
  color: var(--text-light);
}

.highlight-text {
  font-size: 1.2rem;
  line-height: 1.8;
  color: var(--primary-color);
  font-weight: 500;
  padding: 1.5rem;
  background: linear-gradient(135deg, rgba(102, 126, 234, 0.1), rgba(118, 75, 162, 0.1));
  border-radius: var(--radius);
}

.summary-text {
  font-size: 1.05rem;
  line-height: 1.9;
  color: var(--text-color);
  text-align: justify;
}

.review-text {
  font-size: 1rem;
  line-height: 1.8;
  color: var(--text-light);
  font-style: italic;
  padding: 1.5rem;
  background: var(--hover-color);
  border-left: 4px solid var(--primary-color);
  margin: 0;
}

.related-section {
  padding-top: 2rem;
  border-top: 2px solid var(--border-color);
}

.site-footer {
  background: #2c3e50;
  color: #ecf0f1;
  text-align: center;
  padding: 2rem 0;
  margin-top: 3rem;
}

.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 50px;
  height: 50px;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: #fff;
  border: none;
  border-radius: 50%;
  font-size: 1.5rem;
  cursor: pointer;
  box-shadow: var(--shadow-hover);
  opacity: 0;
  visibility: hidden;
  transition: all 0.3s ease;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  transform: translateY(-4px);
}

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

  .intro-text,
  .page-intro {
    font-size: 1rem;
  }

  .section-title {
    font-size: 1.3rem;
  }

  .video-grid,
  .video-grid.large,
  .topic-container,
  .latest-grid {
    grid-template-columns: 1fr;
    gap: 1rem;
  }

  .detail-page {
    padding: 1.5rem;
  }

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

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

  .back-to-top {
    width: 45px;
    height: 45px;
    bottom: 1rem;
    right: 1rem;
  }

  .btn-more {
    display: block;
    margin: 0.5rem 0;
  }
}

@media (max-width: 480px) {
  .hero-section {
    padding: 2rem 1rem;
  }

  .main-content {
    padding: 1rem 0;
  }

  .video-card,
  .topic-card,
  .latest-card {
    padding: 1rem;
  }

  .rank-badge {
    width: 35px;
    height: 35px;
    font-size: 1rem;
  }

  .highlight-text {
    font-size: 1.1rem;
    padding: 1rem;
  }
}