/* Optimized CSS Variables */
:root {
  /* Core Colors */
  --primary: #4285f4;
  --primary-container: #d1e4ff;
  --on-primary: #ffffff;
  --on-primary-container: #001d36;
  
  --surface: #fefbff;
  --on-surface: #1a1c1e;
  --surface-variant: #e1e2ec;
  --on-surface-variant: #44474f;
  --surface-container: #f3f3f3;
  --surface-container-high: #e6e6e6;
  
  --outline: #74777f;
  --outline-variant: #c4c7cf;
  
  /* Elevation */
  --elevation-1: 0 2px 1px -1px rgba(0,0,0,0.2), 0 1px 1px 0 rgba(0,0,0,0.14), 0 1px 3px 0 rgba(0,0,0,0.12);
  --elevation-2: 0 3px 1px -2px rgba(0,0,0,0.2), 0 2px 2px 0 rgba(0,0,0,0.14), 0 1px 5px 0 rgba(0,0,0,0.12);
  --elevation-3: 0 3px 3px -2px rgba(0,0,0,0.2), 0 3px 4px 0 rgba(0,0,0,0.14), 0 1px 8px 0 rgba(0,0,0,0.12);
  --elevation-4: 0 2px 4px -1px rgba(0,0,0,0.2), 0 4px 5px 0 rgba(0,0,0,0.14), 0 1px 10px 0 rgba(0,0,0,0.12);
  
  /* Border Radius */
  --border-radius-sm: 8px;
  --border-radius-md: 12px;
  --border-radius-lg: 16px;
  
  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.2, 0, 0, 1);
  --transition-standard: 250ms cubic-bezier(0.2, 0, 0, 1);
  --transition-emphasized: 400ms cubic-bezier(0.05, 0.7, 0.1, 1);
}

/* Reset and Base Styles */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  height: 100%;
}

body {
  font-family: 'Google Sans', 'Roboto', system-ui, -apple-system, sans-serif;
  background-color: var(--surface);
  color: var(--on-surface);
  line-height: 1.5;
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* App Container */
#app {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header */
.app-header {
  background-color: var(--surface);
  border-bottom: 1px solid var(--outline-variant);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--elevation-1);
  backdrop-filter: blur(8px);
}

.header-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 1200px;
  margin: 0 auto;
  padding: 8px 24px;
  height: 64px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 8px;
  text-decoration: none;
}

.logo-text {
  font-size: 22px;
  font-weight: 400;
  font-family: 'Google Sans', sans-serif;
  color: var(--primary);
}

.nav-menu {
  display: flex;
  gap: 4px;
}

.nav-item {
  background: none;
  border: none;
  padding: 8px 16px;
  border-radius: var(--border-radius-md);
  font-family: inherit;
  font-size: 14px;
  font-weight: 500;
  color: var(--on-surface-variant);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.nav-item:hover {
  background-color: var(--surface-container);
}

.nav-item.active {
  background-color: var(--primary-container);
  color: var(--on-primary-container);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 8px;
}

.icon-button {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: none;
  background: none;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: background-color var(--transition-fast);
  color: var(--on-surface-variant);
}

.icon-button:hover {
  background-color: var(--surface-container);
}

.avatar-button {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  border: none;
  background: none;
  padding: 0;
  cursor: pointer;
  overflow: hidden;
}

.avatar-button img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* Main Content */
.main-content {
  flex: 1;
  background-color: var(--surface);
}

.content-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 24px;
}

/* Video Hero Section */
.video-hero {
  margin-bottom: 32px;
}

.video-container {
  display: grid;
  gap: 24px;
  grid-template-columns: 1fr;
}

.video-player {
  position: relative;
  aspect-ratio: 16/9;
  background-color: #000;
  border-radius: var(--border-radius-lg);
  overflow: hidden;
  box-shadow: var(--elevation-2);
}

.video-player iframe {
  width: 100%;
  height: 100%;
  border: none;
}

.video-overlay {
  position: absolute;
  inset: 0;
  background: rgba(0, 0, 0, 0.3);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: opacity var(--transition-standard);
  pointer-events: none;
}

.video-player:hover .video-overlay {
  opacity: 1;
}

.play-button {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  border: none;
  background-color: var(--primary);
  color: var(--on-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  box-shadow: var(--elevation-3);
  transition: all var(--transition-emphasized);
  pointer-events: auto;
}

.play-button:hover {
  transform: scale(1.1);
  box-shadow: var(--elevation-4);
}

.play-button .material-icons {
  font-size: 32px;
  margin-left: 4px;
}

.video-info {
  padding: 0 4px;
}

.video-title {
  font-size: 28px;
  font-weight: 500;
  color: var(--md-sys-color-on-surface);
  margin-bottom: 8px;
  line-height: 1.3;
}

.video-meta {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 16px;
  font-size: 14px;
  color: var(--md-sys-color-on-surface-variant);
}

.separator {
  opacity: 0.6;
}

.channel-name {
  font-weight: 500;
  color: var(--md-sys-color-on-surface);
}

.video-actions {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.action-button {
  background: none;
  border: none;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  border-radius: var(--md-sys-shape-corner-medium);
  font-family: inherit;
  font-size: 14px;
  font-weight: 500;
  color: var(--md-sys-color-on-surface-variant);
  cursor: pointer;
  transition: background-color var(--md-sys-motion-duration-short4) var(--md-sys-motion-easing-standard);
}

.action-button:hover {
  background-color: var(--md-sys-color-surface-container);
}

/* Carousel Section */
.carousel-section {
  margin-top: 48px;
}

.carousel-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 24px;
}

.carousel-title {
  font-size: 22px;
  font-weight: 500;
  color: var(--md-sys-color-on-surface);
}

.autoplay-toggle {
  display: flex;
  align-items: center;
  gap: 8px;
  background: none;
  border: none;
  font-family: inherit;
  font-size: 14px;
  color: var(--md-sys-color-on-surface-variant);
  cursor: pointer;
  padding: 8px;
  border-radius: var(--md-sys-shape-corner-medium);
  transition: background-color var(--md-sys-motion-duration-short4) var(--md-sys-motion-easing-standard);
}

.autoplay-toggle:hover {
  background-color: var(--md-sys-color-surface-container);
}

.toggle-switch {
  width: 36px;
  height: 20px;
  margin-left: 8px;
}

.toggle-track {
  width: 100%;
  height: 100%;
  background-color: var(--md-sys-color-outline);
  border-radius: 10px;
  position: relative;
  transition: background-color var(--md-sys-motion-duration-short4) var(--md-sys-motion-easing-standard);
}

.toggle-thumb {
  width: 16px;
  height: 16px;
  background-color: var(--md-sys-color-surface);
  border-radius: 50%;
  position: absolute;
  top: 2px;
  left: 2px;
  transition: transform var(--md-sys-motion-duration-short4) var(--md-sys-motion-easing-standard);
  box-shadow: var(--md-sys-elevation-level1);
}

.autoplay-toggle.active .toggle-track {
  background-color: var(--md-sys-color-primary);
}

.autoplay-toggle.active .toggle-thumb {
  transform: translateX(16px);
}

/* Carousel Container */
.carousel-container {
  position: relative;
  display: flex;
  align-items: center;
  gap: 16px;
}

.carousel-nav {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  border: none;
  background-color: var(--md-sys-color-surface-container-high);
  color: var(--md-sys-color-on-surface);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all var(--md-sys-motion-duration-short4) var(--md-sys-motion-easing-standard);
  box-shadow: var(--md-sys-elevation-level2);
  z-index: 10;
  flex-shrink: 0;
}

.carousel-nav:hover {
  background-color: var(--md-sys-color-surface-container-highest);
  box-shadow: var(--md-sys-elevation-level3);
}

.carousel-nav:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.carousel-wrapper {
  flex: 1;
  overflow: hidden;
  position: relative;
}

.carousel-track {
  display: flex;
  gap: 16px;
  transition: transform var(--md-sys-motion-duration-medium4) var(--md-sys-motion-easing-emphasized);
}

/* Video Card */
.video-card {
  flex: 0 0 280px;
  cursor: pointer;
  transition: transform var(--md-sys-motion-duration-short4) var(--md-sys-motion-easing-standard);
}

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

.video-thumbnail {
  position: relative;
  aspect-ratio: 16/9;
  background-color: var(--md-sys-color-surface-variant);
  border-radius: var(--md-sys-shape-corner-medium);
  overflow: hidden;
  margin-bottom: 12px;
  box-shadow: var(--md-sys-elevation-level1);
}

.video-thumbnail img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform var(--md-sys-motion-duration-medium2) var(--md-sys-motion-easing-standard);
}

.video-card:hover .video-thumbnail img {
  transform: scale(1.05);
}

.video-duration {
  position: absolute;
  bottom: 8px;
  right: 8px;
  background-color: rgba(0, 0, 0, 0.8);
  color: white;
  padding: 2px 6px;
  border-radius: var(--md-sys-shape-corner-extra-small);
  font-size: 12px;
  font-weight: 500;
}

.video-card-info {
  padding: 0 4px;
}

.video-card-title {
  font-size: 16px;
  font-weight: 500;
  color: var(--on-surface);
  margin-bottom: 4px;
  line-height: 1.3;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.video-card-meta {
  font-size: 14px;
  color: var(--md-sys-color-on-surface-variant);
  display: flex;
  align-items: center;
  gap: 4px;
}

.video-card-channel {
  font-weight: 400;
}

/* Carousel Pagination */
.carousel-pagination {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin-top: 24px;
}

.pagination-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: var(--md-sys-color-outline-variant);
  cursor: pointer;
  transition: all var(--md-sys-motion-duration-short4) var(--md-sys-motion-easing-standard);
}

.pagination-dot.active {
  background-color: var(--md-sys-color-primary);
  transform: scale(1.25);
}

/* Loading Overlay */
.loading-overlay {
  position: fixed;
  inset: 0;
  background-color: var(--md-sys-color-surface);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  transition: opacity var(--md-sys-motion-duration-medium3) var(--md-sys-motion-easing-standard);
}

.loading-overlay.hidden {
  opacity: 0;
  pointer-events: none;
}

.loading-spinner {
  width: 48px;
  height: 48px;
  margin-bottom: 24px;
}

.spinner-circle {
  width: 100%;
  height: 100%;
  border: 4px solid var(--md-sys-color-outline-variant);
  border-top-color: var(--md-sys-color-primary);
  border-radius: 50%;
  animation: spin 1s linear infinite;
}

.loading-text {
  font-size: 16px;
  color: var(--md-sys-color-on-surface-variant);
  font-weight: 400;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* Responsive Design - Optimized */
@media (max-width: 768px) {
  .header-content { padding: 8px 16px; }
  .nav-menu { display: none; }
  .content-container { padding: 16px; }
  .video-title { font-size: 24px; }
  .carousel-header { 
    flex-direction: column; 
    align-items: flex-start; 
    gap: 16px; 
  }
  .carousel-nav { display: none; }
  .carousel-container { gap: 0; }
  .video-card { flex: 0 0 240px; }
  .video-actions { justify-content: space-between; }
}

@media (max-width: 480px) {
  .content-container { padding: 12px; }
  .video-card { flex: 0 0 200px; }
  .carousel-track { gap: 12px; }
  .video-title { font-size: 20px; }
  .action-button span:not(.material-icons) { display: none; }
}

/* Performance optimizations */
* { 
  box-sizing: border-box; 
}

img { 
  max-width: 100%; 
  height: auto; 
}

/* Reduced motion for accessibility */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}