/*==================== CSS RESET & VARIABLES ====================*/
:root {
  /* Colors */
  --primary-color: #2563eb;
  --text-primary: #1f2937;
  --text-secondary: #6b7280;
  --text-muted: #9ca3af;
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --border-color: #e2e8f0;

  /* Typography */
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;

  /* Spacing */
  --space-4: 1rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;

  /* Layout */
  --max-width: 960px;
  --content-padding: 100px;
  --mobile-padding: 16px;

  /* Effects */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
  --radius-md: 0.375rem;
  --radius-lg: 0.5rem;
  --radius-xl: 0.75rem;
}

/*==================== BASE STYLES ====================*/
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-size-base);
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.2;
  color: var(--text-primary);
}

a {
  text-decoration: none;
  color: inherit;
}

img, video {
  max-width: 100%;
  height: auto;
  display: block;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
}

/*==================== LAYOUT ====================*/
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--content-padding);
}

@media (max-width: 768px) {
  .container {
    padding: 0 var(--mobile-padding);
  }
}

/*==================== NAVIGATION ====================*/
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  z-index: 100;
  backdrop-filter: blur(10px);
}

.nav-container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--content-padding);
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 60px;
}

.nav-brand {
  font-size: var(--font-size-lg);
  font-weight: 600;
  color: var(--text-primary);
}

.nav-links {
  display: flex;
  gap: var(--space-8);
}

.nav-link {
  font-size: var(--font-size-sm);
  color: var(--text-secondary);
  transition: color 0.2s ease;
}

.nav-link:hover {
  color: var(--primary-color);
}

@media (max-width: 768px) {
  .nav-container {
    padding: 0 var(--mobile-padding);
  }

  .nav-links {
    gap: var(--space-4);
  }
}

/*==================== HERO SECTION ====================*/
.hero {
  padding: 120px 0 var(--space-20) 0;
  text-align: center;
  background: var(--bg-secondary);
}

.hero-container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--content-padding);
}

.hero-name {
  font-size: 3.5rem;
  font-weight: 800;
  color: var(--primary-color);
  margin-bottom: var(--space-2);
  letter-spacing: -0.02em;
}

.hero-title {
  font-size: var(--font-size-2xl);
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: var(--space-4);
}

.hero-subtitle {
  font-size: var(--font-size-lg);
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
}

@media (max-width: 768px) {
  .hero {
    padding: 100px 0 var(--space-16) 0;
  }

  .hero-container {
    padding: 0 var(--mobile-padding);
  }

  .hero-name {
    font-size: 2.5rem;
  }

  .hero-title {
    font-size: var(--font-size-xl);
  }
}

/*==================== MAIN CONTENT ====================*/
.main-content {
  padding: var(--space-20) 0;
}

.section {
  margin-bottom: var(--space-20);
}

.section-title {
  font-size: var(--font-size-2xl);
  font-weight: 600;
  color: var(--text-primary);
  text-align: center;
  margin-bottom: var(--space-16);
}

/*==================== CONTENT GRID ====================*/


/* 视频区域 - 2列布局 */
#videos .content-grid {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: flex-start;
  gap: 30px;
  max-width: 1700px;
  margin: 0 auto;
  padding: 0 20px;
}






/*==================== VIDEO STYLES ====================*/
.video-container {
  background: var(--bg-primary);
  border-radius: var(--radius-xl);
  box-shadow: 0 8px 25px rgba(0, 0, 0, 0.1);
  border: 2px solid var(--border-color);
  overflow: hidden;
  transition: all 0.3s ease;
  position: relative;
  width: 810px;
  height: 610px;
  display: flex;
  flex-direction: column;
}

.video-container::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, #ef4444, #f97316);
  opacity: 0;
  transition: opacity 0.3s ease;
}

.video-container:hover {
  box-shadow: 0 12px 35px rgba(0, 0, 0, 0.15);
  transform: translateY(-4px);
  border-color: #ef4444;
}

.video-container:hover::before {
  opacity: 1;
}

.video-header {
  padding: 20px;
  border-bottom: 1px solid var(--border-color);
  background: linear-gradient(135deg, #fef2f2 0%, #fef7f7 100%);
  flex-shrink: 0;
}

.video-title {
  font-size: var(--font-size-xl);
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--space-2);
}

.video-description {
  color: var(--text-secondary);
  font-size: var(--font-size-base);
}

.video-player {
  position: relative;
  width: 100%;
  height: 450px;
  background: #000;
  border-radius: 0;
  flex: 1;
}

.video-player video {
  width: 100%;
  height: 100%;
  object-fit: contain;
  border-radius: 0;
}

.video-controls {
  padding: 15px 20px;
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-shrink: 0;
}

.video-duration {
  font-size: var(--font-size-sm);
  color: var(--text-muted);
  font-weight: 500;
}

/*==================== RESPONSIVE DESIGN ====================*/
@media (max-width: 1800px) {
  /* 大屏幕调整 */
  #videos .content-grid {
    max-width: 1620px;
  }
}

@media (max-width: 1400px) {
  /* 中等屏幕：视频1列 */
  #videos .content-grid {
    max-width: 900px;
  }

  .video-container {
    width: 100%;
    max-width: 810px;
  }
}

@media (max-width: 768px) {
  /* 移动端：全部单列 */
  #videos .content-grid {
    flex-direction: column;
    align-items: center;
    gap: 20px;
  }

  .video-container {
    width: 100%;
    max-width: 500px;
    height: auto;
  }

  .video-player {
    height: 300px;
  }

  .video-header {
    padding: var(--space-4);
  }

  .video-title {
    font-size: var(--font-size-lg);
  }

  .video-controls {
    padding: var(--space-3) var(--space-4);
  }

  .section-title {
    font-size: var(--font-size-xl);
  }
}

/*==================== UTILITY CLASSES ====================*/
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}