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

:root {
  /* Modern Color Palette */
  --primary-color: #2563eb;
  --primary-dark: #1d4ed8;
  --secondary-color: #10b981;
  --accent-color: #f59e0b;
  --background-primary: #0f172a;
  --background-secondary: #1e293b;
  --background-light: #f8fafc;
  --text-primary: #0f172a;
  --text-secondary: #64748b;
  --text-light: #f1f5f9;
  --border-color: #e2e8f0;
  --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);
  --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --gradient-secondary: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
  --gradient-tech: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
}

body {
  font-family: 'Inter', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  line-height: 1.6;
  color: var(--text-primary);
  background: var(--background-light);
  overflow-x: hidden;
}

/* Modern Header Styling */
h1 {
  background: var(--gradient-primary);
  background-clip: text;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  font-weight: 800;
  font-size: 2.5rem;
  text-align: center;
  padding: 2rem 0;
  position: relative;
  animation: fadeInDown 0.8s ease-out;
}

h1::after {
  content: '';
  position: absolute;
  bottom: 1rem;
  left: 50%;
  transform: translateX(-50%);
  width: 100px;
  height: 4px;
  background: var(--gradient-tech);
  border-radius: 2px;
}

/* Modern Navigation */
ul {
  list-style: none;
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  background: rgba(15, 23, 42, 0.95);
  backdrop-filter: blur(10px);
  border-radius: 15px;
  padding: 1rem;
  margin: 0 2rem 2rem;
  box-shadow: var(--shadow-lg);
  position: sticky;
  top: 20px;
  z-index: 100;
  animation: slideInUp 0.8s ease-out 0.2s both;
}

li {
  margin: 0 0.5rem;
}

li a {
  display: block;
  color: var(--text-light);
  text-decoration: none;
  padding: 0.75rem 1.5rem;
  border-radius: 10px;
  font-weight: 500;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  position: relative;
  overflow: hidden;
}

li a::before {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: var(--gradient-tech);
  transition: left 0.3s ease;
  z-index: -1;
}

li a:hover::before {
  left: 0;
}

li a:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

/* Modern Typography */
h2, h3, h4 {
  color: var(--text-primary);
  font-weight: 700;
  margin-bottom: 1rem;
}

h2 {
  font-size: 2rem;
  text-align: center;
  position: relative;
  padding-bottom: 1rem;
}

h2::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 60px;
  height: 3px;
  background: var(--gradient-secondary);
  border-radius: 2px;
}

h3 {
  font-size: 1.5rem;
  color: var(--primary-color);
  font-family: 'Inter', sans-serif;
}

h4 {
  font-size: 1.25rem;
  color: var(--text-secondary);
}

p {
  font-family: 'Inter', sans-serif;
  font-size: 1rem;
  line-height: 1.7;
  color: var(--text-secondary);
  margin-bottom: 1rem;
}

/* Modern Card Design */
.video-item, .content-card {
  background: white;
  border-radius: 20px;
  padding: 2rem;
  margin: 2rem auto;
  max-width: 1200px;
  box-shadow: var(--shadow-md);
  border: 1px solid var(--border-color);
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  position: relative;
  overflow: hidden;
}

.video-item::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--gradient-tech);
}

.video-item:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-lg);
}

/* Modern Tables */
table {
  width: 100%;
  border-collapse: collapse;
  background: white;
  border-radius: 15px;
  overflow: hidden;
  box-shadow: var(--shadow-md);
  margin: 2rem 0;
}

th, td {
  padding: 1rem;
  text-align: left;
  border-bottom: 1px solid var(--border-color);
}

th {
  background: var(--gradient-primary);
  color: white;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  font-size: 0.875rem;
}

tr:hover {
  background: #f8fafc;
  transform: scale(1.01);
  transition: all 0.2s ease;
}

td a {
  color: var(--primary-color);
  text-decoration: none;
  font-weight: 500;
  padding: 0.5rem 1rem;
  border-radius: 8px;
  transition: all 0.3s ease;
  display: inline-block;
}

td a:hover {
  background: var(--primary-color);
  color: white;
  transform: translateY(-1px);
}

/* Modern Code Blocks */
pre {
  background: var(--background-primary);
  color: #e2e8f0;
  border-radius: 15px;
  padding: 2rem;
  margin: 1.5rem 0;
  overflow-x: auto;
  font-family: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;
  font-size: 0.875rem;
  line-height: 1.7;
  border-left: 4px solid var(--accent-color);
  box-shadow: var(--shadow-md);
  position: relative;
}

pre::before {
  content: '{ }';
  position: absolute;
  top: 1rem;
  right: 1rem;
  color: var(--accent-color);
  font-weight: bold;
}

/* Modern Buttons and Links */
.btn, .bookmark-btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  border-radius: 10px;
  text-decoration: none;
  font-weight: 600;
  text-align: center;
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  border: none;
  cursor: pointer;
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.btn-primary {
  background: var(--gradient-primary);
  color: white;
}

.btn-secondary {
  background: var(--gradient-secondary);
  color: white;
}

.btn-tech {
  background: var(--gradient-tech);
  color: white;
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

/* Modern Slideshow */
.slideshow-container {
  max-width: 1000px;
  position: relative;
  margin: 2rem auto;
  border-radius: 20px;
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.mySlides1, .mySlides2, .mySlides3, .mySlides4 {
  display: none;
  position: relative;
}

.mySlides1 img, .mySlides2 img, .mySlides3 img, .mySlides4 img {
  width: 100%;
  height: auto;
  border-radius: 15px;
}

.prev, .next {
  cursor: pointer;
  position: absolute;
  top: 50%;
  width: 50px;
  height: 50px;
  margin-top: -25px;
  color: white;
  font-weight: bold;
  font-size: 18px;
  background: rgba(0, 0, 0, 0.5);
  border: none;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.3s ease;
  backdrop-filter: blur(10px);
}

.next {
  right: 15px;
}

.prev {
  left: 15px;
}

.prev:hover, .next:hover {
  background: var(--primary-color);
  transform: scale(1.1);
}

/* Modern Images */
img.one {
  border: 3px solid var(--primary-color);
  border-radius: 15px;
  transition: all 0.3s ease;
}

img.one:hover {
  transform: rotate(5deg) scale(1.05);
  box-shadow: var(--shadow-lg);
}

.center {
  display: block;
  margin: 2rem auto;
  max-width: 100%;
  border-radius: 15px;
  box-shadow: var(--shadow-md);
}

/* Modern Iframes */
iframe {
  border-radius: 15px;
  box-shadow: var(--shadow-lg);
  border: none;
  transition: all 0.3s ease;
}

iframe:hover {
  transform: scale(1.02);
  box-shadow: var(--shadow-lg);
}

/* Loading Animations */
@keyframes fadeInDown {
  from {
    opacity: 0;
    transform: translateY(-30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes slideInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes pulse {
  0%, 100% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.05);
  }
}

/* Modern Scroll Bar */
::-webkit-scrollbar {
  width: 8px;
}

::-webkit-scrollbar-track {
  background: var(--background-light);
}

::-webkit-scrollbar-thumb {
  background: var(--gradient-primary);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--primary-dark);
}

/* Flash Messages */
.flash-messages {
    margin: 20px auto;
    max-width: 800px;
}

.alert {
    padding: 15px;
    margin-bottom: 10px;
    border-radius: 15px;
    background: linear-gradient(135deg, #d4edda 0%, #c3e6cb 100%);
    color: #155724;
    border: 1px solid #c3e6cb;
    text-align: center;
    font-weight: 500;
    box-shadow: var(--shadow-sm);
    animation: slideInUp 0.5s ease-out;
}

.alert.error {
    background: linear-gradient(135deg, #f8d7da 0%, #f5c6cb 100%);
    color: #721c24;
    border-color: #f5c6cb;
}

/* Modern Footer Styles */
footer {
    background: linear-gradient(135deg, var(--background-primary) 0%, var(--background-secondary) 100%);
    color: var(--text-light);
    padding: 40px 20px 20px;
    margin-top: 50px;
    border-top: 3px solid var(--primary-color);
    position: relative;
}

footer::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--gradient-tech);
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin-bottom: 30px;
}

.footer-section h3 {
    color: var(--primary-color);
    margin-bottom: 15px;
    font-size: 18px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    position: relative;
}

.footer-section h3::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 30px;
    height: 2px;
    background: var(--gradient-tech);
    border-radius: 1px;
}

.footer-section ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

.footer-section ul li {
    margin-bottom: 8px;
    float: none;
}

.footer-section ul li a {
    color: #bdc3c7;
    text-decoration: none;
    transition: all 0.3s ease;
    display: inline-block;
    padding: 5px 0;
    font-weight: 400;
    position: relative;
}

.footer-section ul li a::before {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: width 0.3s ease;
}

.footer-section ul li a:hover::before {
    width: 100%;
}

.footer-section ul li a:hover {
    color: var(--primary-color);
    transform: translateX(5px);
}

.social-links {
    display: flex;
    gap: 15px;
    margin-top: 10px;
    flex-wrap: wrap;
}

.social-links a {
    display: flex;
    align-items: center;
    gap: 8px;
    color: #bdc3c7;
    text-decoration: none;
    transition: all 0.3s ease;
    padding: 8px 12px;
    border-radius: 10px;
    background: rgba(255, 255, 255, 0.05);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.social-links a:hover {
    color: white;
    background: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.social-links img {
    width: 24px;
    height: 24px;
    border-radius: 6px;
    transition: all 0.3s ease;
}

.social-links a:hover img {
    transform: scale(1.1);
}

.footer-bottom {
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    padding-top: 20px;
    text-align: center;
}

.footer-bottom p {
    margin: 5px 0;
    color: #95a5a6;
    font-size: 0.9rem;
    line-height: 1.6;
}

.development-notice {
    background: linear-gradient(135deg, var(--gradient-primary));
    color: white;
    padding: 20px;
    border-radius: 15px;
    margin-bottom: 30px;
    text-align: center;
    box-shadow: var(--shadow-lg);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.development-notice h3 {
    margin-bottom: 10px;
    font-size: 1.2rem;
}

.development-notice p {
    margin: 0;
    opacity: 0.9;
}

/* Video Library Specific Styles */
.user-welcome {
    background: linear-gradient(135deg, #d4edda 0%, #c3e6cb 100%);
    padding: 15px;
    border-radius: 15px;
    margin: 20px 0;
    text-align: center;
    border: 1px solid #c3e6cb;
}

.auth-prompt {
    background: linear-gradient(135deg, #d1ecf1 0%, #bee5eb 100%);
    padding: 15px;
    border-radius: 15px;
    margin: 20px 0;
    text-align: center;
    border: 1px solid #bee5eb;
}

/* Contents Section */
.contents-section {
    background: white;
    border-radius: 20px;
    padding: 2rem;
    margin: 2rem 0;
    box-shadow: var(--shadow-md);
    border-left: 4px solid var(--primary-color);
}

.contents-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    margin-top: 1rem;
}

.contents-column h4 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-size: 1.2rem;
}

.contents-links {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.content-link {
    color: var(--text-secondary);
    text-decoration: none;
    padding: 0.5rem;
    border-radius: 8px;
    transition: all 0.3s ease;
    font-size: 0.9rem;
    border-left: 3px solid transparent;
}

.content-link:hover {
    background: var(--background-light);
    border-left-color: var(--primary-color);
    transform: translateX(5px);
    color: var(--primary-color);
}

/* Video Items */
.video-item {
    background: white;
    border-radius: 20px;
    padding: 2rem;
    margin: 3rem 0;
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
}

.video-item::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--gradient-tech);
}

.video-item:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.video-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.video-header h3 {
    color: var(--text-primary);
    margin: 0;
    flex: 1;
    min-width: 300px;
}

.video-meta {
    display: flex;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
}

/* Category Badges */
.category-badge {
    background: var(--gradient-primary);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.category-python-basics { background: var(--gradient-primary); }
.category-gui-programming { background: var(--gradient-secondary); }
.category-data-analysis { background: var(--gradient-tech); }
.category-short-tutorials { background: linear-gradient(135deg, #ff9a9e 0%, #fecfef 100%); }
.category-ai-humor { background: linear-gradient(135deg, #a8edea 0%, #fed6e3 100%); }
.category-web-development { background: linear-gradient(135deg, #ff8a80 0%, #ea4335 100%); }

/* Bookmark Button */
.bookmark-btn {
    background: var(--gradient-secondary);
    color: white;
    padding: 0.75rem 1.5rem;
    border-radius: 25px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s ease;
    font-size: 0.9rem;
    border: none;
    cursor: pointer;
}

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

.bookmark-btn.bookmarked {
    background: var(--gradient-tech);
    animation: pulse 1s ease-in-out;
}

/* Video Container */
.video-container {
    position: relative;
    width: 100%;
    height: 0;
    padding-bottom: 56.25%; /* 16:9 aspect ratio */
    margin: 1.5rem 0;
    border-radius: 15px;
    overflow: hidden;
    box-shadow: var(--shadow-md);
}

.video-container iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
    border-radius: 15px;
}

.video-description {
    background: var(--background-light);
    padding: 1.5rem;
    border-radius: 15px;
    margin-top: 1rem;
    border-left: 4px solid var(--accent-color);
}

.video-description p {
    margin: 0;
    line-height: 1.7;
    color: var(--text-secondary);
}

/* Playlists Section */
.playlists-section {
    margin: 4rem 0;
    padding: 2rem 0;
}

.playlist-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

.playlist-item {
    background: white;
    border-radius: 20px;
    padding: 2rem;
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

.playlist-item:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.playlist-item h4 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    font-size: 1.3rem;
}

.playlist-item iframe {
    width: 100%;
    height: 250px;
    border-radius: 15px;
    margin-bottom: 1rem;
}

.playlist-item p {
    color: var(--text-secondary);
    margin: 0;
    font-style: italic;
}

/* Back to Top Button */
.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 50px;
    height: 50px;
    background: var(--gradient-primary);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    font-size: 1.5rem;
    font-weight: bold;
    box-shadow: var(--shadow-lg);
    transition: all 0.3s ease;
    z-index: 1000;
}

.back-to-top:hover {
    transform: scale(1.1);
    background: var(--gradient-tech);
}

/* No Content State */
.no-content {
    text-align: center;
    padding: 4rem 2rem;
    background: var(--background-light);
    border-radius: 20px;
    margin: 2rem 0;
}

.no-content h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.no-content p {
    color: var(--text-secondary);
    margin-bottom: 2rem;
    max-width: 500px;
    margin-left: auto;
    margin-right: auto;
}

/* Admin Styles */
.admin-header {
    text-align: center;
    margin-bottom: 2rem;
}

.admin-nav {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin: 2rem 0;
    flex-wrap: wrap;
}

.admin-nav-item {
    background: var(--background-secondary);
    color: var(--text-light);
    padding: 1rem 1.5rem;
    border-radius: 15px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s ease;
    border: 2px solid transparent;
}

.admin-nav-item:hover, .admin-nav-item.active {
    background: var(--gradient-primary);
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin: 2rem 0;
}

.stat-card {
    background: white;
    border-radius: 20px;
    padding: 2rem;
    box-shadow: var(--shadow-md);
    border-left: 4px solid var(--primary-color);
    display: flex;
    align-items: center;
    gap: 1rem;
    transition: all 0.3s ease;
}

.stat-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.stat-icon {
    font-size: 2.5rem;
    background: var(--gradient-primary);
    background-clip: text;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.stat-info h3 {
    font-size: 2rem;
    margin: 0;
    color: var(--primary-color);
}

.stat-info p {
    margin: 0;
    color: var(--text-secondary);
    font-weight: 500;
}

.admin-section {
    background: white;
    border-radius: 20px;
    padding: 2rem;
    margin: 2rem 0;
    box-shadow: var(--shadow-md);
}

.quick-actions {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
    margin-top: 1rem;
}

.action-card {
    background: var(--background-light);
    border-radius: 15px;
    padding: 2rem;
    text-decoration: none;
    text-align: center;
    transition: all 0.3s ease;
    border: 2px solid var(--border-color);
}

.action-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.action-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
    background: var(--gradient-tech);
    background-clip: text;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.action-card h4 {
    color: var(--primary-color);
    margin: 0.5rem 0;
}

.action-card p {
    color: var(--text-secondary);
    margin: 0;
}

/* Form Styles */
.form-container {
    max-width: 800px;
    margin: 0 auto;
}

.video-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.form-group {
    display: flex;
    flex-direction: column;
}

.form-group label {
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.form-group input,
.form-group select,
.form-group textarea {
    padding: 1rem;
    border: 2px solid var(--border-color);
    border-radius: 10px;
    font-size: 1rem;
    transition: all 0.3s ease;
    font-family: inherit;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-group small {
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin-top: 0.25rem;
}

.form-actions {
    display: flex;
    gap: 1rem;
    margin-top: 1rem;
}

.admin-table {
    width: 100%;
    border-collapse: collapse;
    margin: 1rem 0;
}

.admin-table th,
.admin-table td {
    padding: 1rem;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}

.admin-table th {
    background: var(--gradient-primary);
    color: white;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    font-size: 0.875rem;
}

.admin-table tr:hover {
    background: var(--background-light);
}

.badge {
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.badge-admin {
    background: var(--gradient-secondary);
    color: white;
}

.badge-user {
    background: var(--gradient-tech);
    color: white;
}

.btn-sm {
    padding: 0.5rem 1rem;
    border-radius: 8px;
    text-decoration: none;
    font-size: 0.8rem;
    font-weight: 600;
    border: none;
    cursor: pointer;
    margin: 0 0.25rem;
    transition: all 0.3s ease;
}

.btn-primary { background: var(--primary-color); color: white; }
.btn-secondary { background: var(--text-secondary); color: white; }
.btn-success { background: var(--secondary-color); color: white; }
.btn-warning { background: var(--accent-color); color: white; }
.btn-danger { background: #dc3545; color: white; }

.btn-sm:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

.bookmark-count {
    background: var(--gradient-tech);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: 15px;
    font-weight: 600;
}

.table-container {
    overflow-x: auto;
}

@media (max-width: 768px) {
    .admin-nav {
        flex-direction: column;
        align-items: center;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .form-actions {
        flex-direction: column;
    }
    
    .admin-table {
        font-size: 0.875rem;
    }
    
    .admin-table th,
    .admin-table td {
        padding: 0.75rem 0.5rem;
    }
}

/* Center alignment for footer links on mobile */
@media (max-width: 768px) {
    .footer-section ul {
        text-align: center;
    }
    
    .footer-section ul li a:hover {
        transform: translateY(-2px);
    }
}

@media (max-width: 768px) {
    .contents-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
    }
    
    .video-header {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .video-meta {
        width: 100%;
        justify-content: space-between;
    }
    
    .playlist-grid {
        grid-template-columns: 1fr;
    }
    
    .video-container {
        padding-bottom: 75%; /* Adjust for mobile */
    }
    
    .back-to-top {
        bottom: 1rem;
        right: 1rem;
        width: 45px;
        height: 45px;
    }
}

@media (max-width: 480px) {
    .video-item, .contents-section {
        padding: 1rem;
        margin: 1rem 0;
    }
    
    .playlist-item {
        padding: 1rem;
    }
    
    .video-header h3 {
        font-size: 1.1rem;
    }
}

/* Admin Users and Navbar Links Styles */
.user-stats {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.stat-pill {
    background: var(--gradient-tech);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 600;
}

.current-user-badge {
    background: var(--gradient-secondary);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 15px;
    font-size: 0.8rem;
    font-weight: 600;
    margin-left: 0.5rem;
}

.inactive-row {
    opacity: 0.6;
    background: #f8f9fa;
}

.order-badge {
    background: var(--primary-color);
    color: white;
    padding: 0.5rem 0.75rem;
    border-radius: 50%;
    font-weight: bold;
    font-size: 0.9rem;
}

.url-display {
    background: var(--background-light);
    padding: 0.25rem 0.5rem;
    border-radius: 6px;
    font-size: 0.85rem;
    max-width: 200px;
    display: inline-block;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.external-link {
    margin-left: 0.5rem;
    text-decoration: none;
    color: var(--primary-color);
}

.badge-success {
    background: var(--secondary-color);
    color: white;
}

.badge-inactive {
    background: var(--text-secondary);
    color: white;
}

.link-examples {
    background: var(--background-light);
    padding: 1.5rem;
    border-radius: 15px;
    margin: 1rem 0;
}

.examples-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1rem;
    margin-top: 1rem;
}

.example-item {
    background: white;
    padding: 1rem;
    border-radius: 10px;
    border: 2px solid var(--border-color);
    cursor: pointer;
    transition: all 0.3s ease;
}

.example-item:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
}

.example-item strong {
    display: block;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.example-item code {
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.admin-info {
    background: var(--background-light);
    padding: 1.5rem;
    border-radius: 15px;
    margin-top: 2rem;
    border-left: 4px solid var(--accent-color);
}

.admin-info h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.admin-info ul {
    list-style: none;
    padding: 0;
}

.admin-info li {
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-color);
}

.admin-info li:last-child {
    border-bottom: none;
}

.admin-info strong {
    color: var(--primary-color);
}

.no-content {
    text-align: center;
    padding: 4rem 2rem;
    background: var(--background-light);
    border-radius: 20px;
    margin: 2rem 0;
}

.no-content h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.no-content p {
    color: var(--text-secondary);
    margin-bottom: 2rem;
    max-width: 500px;
    margin-left: auto;
    margin-right: auto;
}

@media (max-width: 768px) {
    .user-stats {
        flex-direction: column;
    }
    
    .examples-grid {
        grid-template-columns: 1fr;
    }
    
    .url-display {
        max-width: 150px;
    }
}