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

body {
  font-family: 'Microsoft YaHei', 'PingFang SC', 'Helvetica Neue', Arial, sans-serif;
  background: #f5f5f5;
  color: #333;
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a {
  color: #1a73e8;
  text-decoration: none;
  transition: color 0.3s;
}

a:hover {
  color: #1557b0;
  text-decoration: underline;
}

/* Header Styles */
header {
  background: #ffffff;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  position: sticky;
  top: 0;
  z-index: 1000;
}

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

.header-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 60px;
}

.logo {
  font-size: 24px;
  font-weight: bold;
  color: #1a73e8;
  cursor: pointer;
  white-space: nowrap;
}

nav {
  display: flex;
  flex-wrap: nowrap;
  align-items: center;
  gap: 20px;
}

nav a {
  white-space: nowrap;
  font-size: 15px;
  padding: 8px 12px;
  border-radius: 4px;
  transition: background 0.3s;
}

nav a:hover {
  background: #e3f2fd;
  text-decoration: none;
}

/* Main Content */
main {
  flex: 1;
  padding: 30px 20px;
}

/* Hero Section */
.hero {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: #fff;
  padding: 60px 20px;
  text-align: center;
  border-radius: 8px;
  margin-bottom: 40px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
}

.hero h1 {
  font-size: 32px;
  margin-bottom: 15px;
  font-weight: 600;
}

.hero p {
  font-size: 16px;
  opacity: 0.95;
  max-width: 800px;
  margin: 0 auto;
  line-height: 1.8;
}

/* Section Styles */
section {
  background: #ffffff;
  border-radius: 8px;
  padding: 30px;
  margin-bottom: 30px;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

h1 {
  font-size: 28px;
  color: #1a73e8;
  margin-bottom: 20px;
  font-weight: 600;
}

h2 {
  font-size: 24px;
  color: #1a73e8;
  margin-bottom: 20px;
  padding-bottom: 10px;
  border-bottom: 2px solid #1a73e8;
  font-weight: 600;
}

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

.video-card {
  background: #ffffff;
  border: 1px solid #e0e0e0;
  border-radius: 6px;
  padding: 15px;
  transition: all 0.3s ease;
  cursor: pointer;
}

.video-card:hover {
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
  transform: translateY(-2px);
  border-color: #1a73e8;
}

.video-card h3 {
  font-size: 16px;
  margin-bottom: 10px;
  color: #333;
  font-weight: 600;
}

.video-card .meta {
  font-size: 12px;
  color: #999;
  margin-bottom: 8px;
}

.video-card p {
  font-size: 13px;
  color: #666;
  line-height: 1.6;
}

/* Tags */
.tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 15px 0;
}

.tag {
  background: #e3f2fd;
  color: #1976d2;
  padding: 5px 12px;
  border-radius: 20px;
  font-size: 13px;
  white-space: nowrap;
}

/* Buttons */
.link-btn {
  display: inline-block;
  background: #1a73e8;
  color: #fff;
  padding: 12px 24px;
  border-radius: 6px;
  font-size: 15px;
  transition: all 0.3s;
  text-decoration: none;
  font-weight: 500;
}

.link-btn:hover {
  background: #1557b0;
  text-decoration: none;
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(26, 115, 232, 0.3);
}

/* Footer */
footer {
  background: #333;
  color: #fff;
  text-align: center;
  padding: 20px;
  margin-top: 50px;
}

footer p {
  font-size: 14px;
  opacity: 0.9;
}

/* Responsive Design */
@media (max-width: 768px) {
  nav {
    gap: 5px;
    font-size: 13px;
  }

  nav a {
    flex: 1 1 0;
    min-width: 0;
    text-align: center;
    padding: 5px 3px;
    overflow: hidden;
    text-overflow: ellipsis;
  }

  .hero h1 {
    font-size: 24px;
  }

  .hero {
    padding: 40px 15px;
  }

  h1 {
    font-size: 22px;
  }

  h2 {
    font-size: 20px;
  }

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

  section {
    padding: 20px;
  }
}

/* UI Style Variations */
body.ui-style-5 {
  --primary-color: #1a73e8;
  --secondary-color: #667eea;
  --accent-color: #764ba2;
}

body.ui-style-5 .hero {
  background: linear-gradient(135deg, var(--secondary-color) 0%, var(--accent-color) 100%);
}

/* Smooth Scrolling */
html {
  scroll-behavior: smooth;
}

/* Selection */
::selection {
  background: #1a73e8;
  color: #fff;
}