:root {
  --primary-color: #2c5f7f;
  --secondary-color: #4a8bad;
  --accent-color: #f39c12;
  --text-primary: #2c3e50;
  --text-secondary: #7f8c8d;
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fa;
  --border-color: #e1e8ed;
  --hover-bg: #ecf0f1;
  --shadow-sm: 0 2px 4px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.12);
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", "微软雅黑", sans-serif;
  line-height: 1.6;
  color: var(--text-primary);
  background: var(--bg-secondary);
}

a {
  color: var(--primary-color);
  text-decoration: none;
  transition: color 0.3s ease;
}

a:hover {
  color: var(--secondary-color);
}

header {
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: 0;
  z-index: 1000;
}

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

.logo {
  font-size: 24px;
  font-weight: 700;
  color: var(--primary-color);
  padding: 15px 0;
  display: inline-block;
}

nav {
  border-top: 1px solid var(--border-color);
}

.nav-list {
  display: flex;
  flex-wrap: nowrap;
  justify-content: space-between;
  align-items: center;
  list-style: none;
  padding: 0;
  margin: 0;
}

.nav-list li {
  flex: 1 1 0;
  min-width: 0;
  text-align: center;
}

.nav-list a {
  display: block;
  padding: 12px 8px;
  color: var(--text-primary);
  font-size: 15px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  transition: background 0.3s ease, color 0.3s ease;
}

.nav-list a:hover {
  background: var(--hover-bg);
  color: var(--primary-color);
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 30px 20px;
}

h1 {
  font-size: 28px;
  line-height: 1.3;
  margin-bottom: 20px;
  color: var(--text-primary);
}

h2 {
  font-size: 22px;
  line-height: 1.4;
  margin: 30px 0 15px;
  color: var(--text-primary);
  border-left: 4px solid var(--primary-color);
  padding-left: 12px;
}

h3 {
  font-size: 18px;
  line-height: 1.4;
  margin: 20px 0 10px;
  color: var(--text-primary);
}

p {
  margin-bottom: 15px;
  line-height: 1.8;
}

section {
  background: var(--bg-primary);
  border-radius: 8px;
  padding: 25px;
  margin-bottom: 25px;
  box-shadow: var(--shadow-sm);
}

.intro-section {
  border-left: 4px solid var(--accent-color);
}

.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
  margin-top: 20px;
}

.video-card {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 18px;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.video-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.video-card h3 {
  margin: 0 0 10px;
  font-size: 18px;
}

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

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

.video-meta {
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 8px;
}

.video-meta span {
  margin-right: 12px;
}

.video-desc {
  font-size: 14px;
  line-height: 1.6;
  color: var(--text-secondary);
  margin-top: 10px;
}

.video-list {
  list-style: none;
}

.video-list li {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 15px;
  margin-bottom: 12px;
  transition: background 0.3s ease;
}

.video-list li:hover {
  background: var(--hover-bg);
}

.video-list h3 {
  margin: 0 0 8px;
  font-size: 17px;
}

.detail-header {
  margin-bottom: 25px;
}

.info-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 15px;
  margin: 20px 0;
}

.info-item {
  padding: 12px;
  background: var(--bg-secondary);
  border-radius: 6px;
}

.info-item strong {
  color: var(--primary-color);
  display: block;
  margin-bottom: 5px;
}

.tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 8px;
}

.tag {
  display: inline-block;
  padding: 4px 12px;
  background: var(--bg-secondary);
  border-radius: 4px;
  font-size: 13px;
  color: var(--text-secondary);
}

.summary-section, .review-section {
  margin-top: 25px;
}

.rank-number {
  display: inline-block;
  width: 30px;
  height: 30px;
  line-height: 30px;
  text-align: center;
  background: var(--primary-color);
  color: white;
  border-radius: 4px;
  font-weight: 700;
  margin-right: 10px;
}

.rank-number.top3 {
  background: var(--accent-color);
}

.date-label {
  display: inline-block;
  padding: 3px 8px;
  background: var(--bg-secondary);
  border-radius: 3px;
  font-size: 12px;
  color: var(--text-secondary);
  margin-left: 8px;
}

footer {
  background: var(--bg-primary);
  border-top: 1px solid var(--border-color);
  padding: 25px 20px;
  text-align: center;
  color: var(--text-secondary);
  font-size: 14px;
  margin-top: 40px;
}

@media (max-width: 768px) {
  .container {
    padding: 20px 15px;
  }

  h1 {
    font-size: 24px;
  }

  h2 {
    font-size: 20px;
  }

  .logo {
    font-size: 20px;
    padding: 12px 0;
  }

  .nav-list a {
    padding: 10px 4px;
    font-size: 13px;
  }

  .video-grid {
    grid-template-columns: 1fr;
    gap: 15px;
  }

  section {
    padding: 18px;
    margin-bottom: 18px;
  }
}

@media (max-width: 480px) {
  .header-container {
    padding: 0 12px;
  }

  .logo {
    font-size: 18px;
  }

  .nav-list a {
    padding: 8px 2px;
    font-size: 12px;
  }

  h1 {
    font-size: 20px;
  }

  h2 {
    font-size: 18px;
  }
}