/* Layout Variables */
:root {
  --max-width: 1200px;
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
}

/* Typography */
body {
  font-size: 16px;
  line-height: 1.6;
}

h1 { font-size: 2rem; line-height: 1.2; margin-bottom: var(--spacing-md); font-weight: 700; }
h2 { font-size: 1.5rem; line-height: 1.2; margin: var(--spacing-lg) 0 var(--spacing-md); font-weight: 600; }
h3 { font-size: 1.25rem; line-height: 1.3; margin: var(--spacing-md) 0 var(--spacing-sm); font-weight: 600; }
h4 { font-size: 1.1rem; line-height: 1.3; margin: var(--spacing-sm) 0; font-weight: 600; }

p { margin-bottom: var(--spacing-sm); }

/* Header */
header {
  background: #fff;
  border-bottom: 2px solid #0066cc;
  padding: var(--spacing-md) 0;
}

.logo {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

.logo a {
  font-size: 1.75rem;
  font-weight: 700;
  color: #0066cc;
  text-decoration: none;
}

.logo a:hover {
  color: #0052a3;
}

/* Navigation enhancements */
nav {
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

nav a.active {
  background: #e6f2ff;
  color: #0066cc;
  font-weight: 600;
}

/* Main content */
main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--spacing-lg) var(--spacing-md);
  background: #fff;
  min-height: 60vh;
}

/* Hero section */
.hero {
  text-align: center;
  padding: var(--spacing-xl) 0 var(--spacing-lg);
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: #fff;
  margin: calc(var(--spacing-lg) * -1) calc(var(--spacing-md) * -1) var(--spacing-lg);
  padding-left: var(--spacing-md);
  padding-right: var(--spacing-md);
}

.hero h1 {
  margin-bottom: var(--spacing-sm);
  color: #fff;
}

.hero .subtitle {
  font-size: 1.1rem;
  opacity: 0.95;
}

/* Intro section */
.intro {
  background: #f8f9fa;
  padding: var(--spacing-lg);
  border-radius: 8px;
  margin-bottom: var(--spacing-lg);
  line-height: 1.8;
}

/* Video grid */
.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--spacing-md);
  margin: var(--spacing-md) 0;
}

.video-card {
  background: #fff;
  border: 1px solid #e0e0e0;
  border-radius: 8px;
  padding: var(--spacing-md);
  transition: all 0.3s ease;
}

.video-card:hover {
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
  transform: translateY(-2px);
}

.video-card h3,
.video-card h4 {
  margin-top: 0;
}

.video-card .meta {
  color: #666;
  font-size: 0.9rem;
  margin: var(--spacing-xs) 0;
}

.video-card .one-line {
  color: #555;
  font-size: 0.95rem;
  margin: var(--spacing-sm) 0;
  line-height: 1.5;
}

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

.video-card .link {
  display: inline-block;
  margin-top: var(--spacing-sm);
  color: #0066cc;
  font-weight: 500;
}

/* Video list */
.video-list {
  list-style: none;
}

.video-list li {
  padding: var(--spacing-sm) 0;
  border-bottom: 1px solid #f0f0f0;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--spacing-xs);
}

.video-list li:last-child {
  border-bottom: none;
}

.video-list a {
  font-weight: 500;
  flex: 1;
}

.video-list .meta {
  color: #888;
  font-size: 0.9rem;
}

/* Sections */
.hot-list,
.latest-list,
.quick-links {
  margin: var(--spacing-xl) 0;
}

.more-link {
  text-align: center;
  margin-top: var(--spacing-md);
}

.more-link a {
  font-size: 1.05rem;
  font-weight: 500;
}

/* Quick links */
.link-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-md);
  margin-top: var(--spacing-md);
}

.quick-link-card {
  background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
  padding: var(--spacing-lg);
  border-radius: 8px;
  display: block;
  text-decoration: none;
  color: #333;
  transition: all 0.3s ease;
}

.quick-link-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 16px rgba(0,0,0,0.15);
  text-decoration: none;
}

.quick-link-card h3 {
  color: #0066cc;
  margin: 0 0 var(--spacing-xs);
}

.quick-link-card p {
  margin: 0;
  color: #555;
}

/* List pages */
.page-header {
  text-align: center;
  margin-bottom: var(--spacing-xl);
  padding-bottom: var(--spacing-lg);
  border-bottom: 2px solid #f0f0f0;
}

.page-desc {
  color: #666;
  font-size: 1.05rem;
  line-height: 1.8;
  max-width: 800px;
  margin: 0 auto;
}

.list-group,
.topic-group {
  margin-bottom: var(--spacing-xl);
}

.group-title,
.topic-title {
  background: #f8f9fa;
  padding: var(--spacing-sm) var(--spacing-md);
  border-left: 4px solid #0066cc;
  margin-bottom: var(--spacing-md);
}

.ranked-list {
  list-style: none;
  counter-reset: rank;
}

.ranked-list li {
  display: flex;
  gap: var(--spacing-md);
  padding: var(--spacing-md);
  margin-bottom: var(--spacing-md);
  background: #fff;
  border: 1px solid #e0e0e0;
  border-radius: 8px;
  counter-increment: rank;
}

.ranked-list .rank {
  font-size: 1.5rem;
  font-weight: 700;
  color: #0066cc;
  min-width: 40px;
  text-align: center;
}

.ranked-list .rank::before {
  content: counter(rank);
}

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

.ranked-list h3 {
  margin-top: 0;
}

.latest-item {
  display: flex;
  gap: var(--spacing-md);
  padding: var(--spacing-md);
  margin-bottom: var(--spacing-md);
  border: 1px solid #e0e0e0;
  border-radius: 8px;
  background: #fff;
}

.latest-item .date {
  font-size: 1.25rem;
  font-weight: 700;
  color: #0066cc;
  min-width: 60px;
  text-align: center;
}

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

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

.latest-item .summary {
  color: #666;
  font-size: 0.95rem;
  line-height: 1.6;
}

/* Detail page */
.video-detail {
  max-width: 900px;
  margin: 0 auto;
}

.detail-header {
  text-align: center;
  margin-bottom: var(--spacing-xl);
  padding-bottom: var(--spacing-lg);
  border-bottom: 2px solid #f0f0f0;
}

.detail-header .subtitle {
  color: #888;
  font-size: 1.05rem;
}

.basic-info dl {
  display: grid;
  grid-template-columns: 120px 1fr;
  gap: var(--spacing-sm) var(--spacing-md);
  background: #f8f9fa;
  padding: var(--spacing-lg);
  border-radius: 8px;
}

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

.basic-info dd {
  margin: 0;
  color: #333;
}

.one-line,
.summary,
.review,
.related {
  margin-top: var(--spacing-xl);
}

.one-line p {
  font-size: 1.1rem;
  line-height: 1.8;
  color: #444;
  background: #fff9e6;
  padding: var(--spacing-md);
  border-left: 4px solid #ffcc00;
  border-radius: 4px;
}

.summary p,
.review p {
  line-height: 1.8;
  color: #444;
  text-indent: 2em;
}

/* Footer */
footer {
  background: #333;
  color: #fff;
  text-align: center;
  padding: var(--spacing-lg);
  margin-top: var(--spacing-xl);
}

footer p {
  margin: 0;
}

/* Responsive */
@media (max-width: 768px) {
  :root {
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
  }

  h1 { font-size: 1.5rem; }
  h2 { font-size: 1.25rem; }

  .logo a { font-size: 1.5rem; }

  .hero {
    padding-top: var(--spacing-lg);
    padding-bottom: var(--spacing-md);
  }

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

  .basic-info dl {
    grid-template-columns: 100px 1fr;
    gap: var(--spacing-xs) var(--spacing-sm);
  }

  .ranked-list li,
  .latest-item {
    flex-direction: column;
    gap: var(--spacing-sm);
  }

  .ranked-list .rank,
  .latest-item .date {
    min-width: auto;
    text-align: left;
  }
}

/* UI Style variations */
.ui-style-0 { --primary-color: #0066cc; }
.ui-style-1 { --primary-color: #2c3e50; }
.ui-style-2 { --primary-color: #27ae60; }
.ui-style-3 { --primary-color: #e74c3c; }
.ui-style-4 { --primary-color: #9b59b6; }
.ui-style-5 { --primary-color: #f39c12; }
.ui-style-6 { --primary-color: #1abc9c; }
.ui-style-7 { --primary-color: #34495e; }
.ui-style-8 { --primary-color: #16a085; }
.ui-style-9 { --primary-color: #c0392b; }
.ui-style-10 { --primary-color: #8e44ad; }
.ui-style-11 { --primary-color: #d35400; }
.ui-style-12 { --primary-color: #2980b9; }
.ui-style-13 { --primary-color: #7f8c8d; }
.ui-style-14 { --primary-color: #c2185b; }
.ui-style-15 { --primary-color: #00897b; }