/* ===== CSS Variables ===== */
:root {
    /* Colors - Dark Theme (Default) */
    --bg-primary: #0a1628;
    --bg-secondary: #122036;
    --bg-card: #1a2d4a;
    --bg-card-hover: #223654;
    --text-primary: #ffffff;
    --text-secondary: #a0aec0;
    --text-muted: #718096;
    --accent-primary: #00d4aa;
    --accent-secondary: #00b894;
    --accent-gradient: linear-gradient(135deg, #00d4aa 0%, #00b894 100%);
    --border-color: #2d3748;
    --shadow-color: rgba(0, 0, 0, 0.3);
    --danger: #e53e3e;
    --warning: #ed8936;
    --success: #48bb78;
    --info: #4299e1;
    
    /* Spacing */
    --sidebar-width: 260px;
    --sidebar-collapsed: 70px;
    --header-height: 70px;
    --border-radius: 12px;
    --border-radius-sm: 8px;
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
}

/* Light Theme */
[data-theme="light"] {
    --bg-primary: #f7fafc;
    --bg-secondary: #ffffff;
    --bg-card: #ffffff;
    --bg-card-hover: #f0f4f8;
    --text-primary: #1a202c;
    --text-secondary: #4a5568;
    --text-muted: #718096;
    --border-color: #e2e8f0;
    --shadow-color: rgba(0, 0, 0, 0.1);
}

/* ===== Reset & Base ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
}

a {
    color: var(--accent-primary);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--accent-secondary);
}

/* ===== Sidebar ===== */
.sidebar {
    position: fixed;
    left: 0;
    top: 0;
    width: var(--sidebar-width);
    height: 100vh;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    z-index: 1000;
    transition: width var(--transition-normal);
    display: flex;
    flex-direction: column;
}

.sidebar.collapsed {
    width: var(--sidebar-collapsed);
}

.sidebar-header {
    padding: 20px;
    display: flex;
    align-items: center;
    gap: 12px;
    border-bottom: 1px solid var(--border-color);
    min-height: var(--header-height);
}

.sidebar-header i {
    font-size: 28px;
    color: var(--accent-primary);
}

.sidebar-header span {
    font-size: 20px;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    white-space: nowrap;
}

.sidebar.collapsed .sidebar-header span {
    display: none;
}

.sidebar-menu {
    list-style: none;
    padding: 15px 10px;
    flex: 1;
}

.sidebar-menu li {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 16px;
    margin-bottom: 5px;
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
    color: var(--text-secondary);
}

.sidebar-menu li:hover {
    background: var(--bg-card);
    color: var(--text-primary);
}

.sidebar-menu li.active {
    background: var(--accent-gradient);
    color: white;
}

.sidebar-menu li i {
    font-size: 18px;
    width: 24px;
    text-align: center;
}

.sidebar.collapsed .sidebar-menu li span {
    display: none;
}

/* ===== Main Content ===== */
.main-content {
    margin-left: var(--sidebar-width);
    min-height: 100vh;
    transition: margin-left var(--transition-normal);
}

.sidebar.collapsed + .main-content {
    margin-left: var(--sidebar-collapsed);
}

/* ===== Header ===== */
.header {
    position: sticky;
    top: 0;
    height: var(--header-height);
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    padding: 0 30px;
    gap: 20px;
    z-index: 100;
}

.menu-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--text-primary);
    font-size: 20px;
    cursor: pointer;
    padding: 8px;
}

.search-container {
    flex: 1;
    display: flex;
    gap: 12px;
    max-width: 700px;
}

.search-container input {
    flex: 1;
    padding: 12px 20px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 50px;
    color: var(--text-primary);
    font-size: 15px;
    transition: all var(--transition-fast);
}

.search-container input:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(0, 212, 170, 0.1);
}

.search-container input::placeholder {
    color: var(--text-muted);
}

.header-spacer {
    flex: 1;
}

.theme-toggle {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    width: 44px;
    height: 44px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    transition: all var(--transition-fast);
}

.theme-toggle:hover {
    background: var(--bg-card-hover);
    transform: rotate(15deg);
}

/* ===== Buttons ===== */
.btn-primary {
    padding: 12px 24px;
    background: var(--accent-gradient);
    border: none;
    border-radius: 50px;
    color: white;
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 20px rgba(0, 212, 170, 0.4);
}

.btn-primary:active {
    transform: translateY(0);
}

.btn-secondary {
    padding: 10px 20px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    color: var(--text-primary);
    font-size: 14px;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: all var(--transition-fast);
    width: 100%;
    justify-content: center;
    margin-bottom: 10px;
}

.btn-secondary:hover {
    background: var(--bg-card-hover);
    border-color: var(--accent-primary);
}

.btn-danger {
    padding: 12px 24px;
    background: var(--danger);
    border: none;
    border-radius: var(--border-radius-sm);
    color: white;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: all var(--transition-fast);
}

.btn-danger:hover {
    background: #c53030;
}

/* ===== Pages ===== */
.page {
    display: none;
    padding: 30px;
    animation: fadeIn 0.3s ease;
}

.page.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ===== Hero Section ===== */
.hero-section {
    text-align: center;
    padding: 60px 20px;
    max-width: 1000px;
    margin: 0 auto;
}

.hero-section h1 {
    font-size: 48px;
    margin-bottom: 20px;
    font-weight: 700;
}

.gradient-text {
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-section > p {
    font-size: 18px;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 40px;
}

/* ===== Topic Suggestions ===== */
.topic-suggestions {
    margin-bottom: 50px;
}

.topic-suggestions h3 {
    margin-bottom: 15px;
    color: var(--text-secondary);
    font-weight: 500;
}

.suggestion-chips {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 10px;
}

.chip {
    padding: 10px 20px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 50px;
    color: var(--text-primary);
    font-size: 14px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.chip:hover {
    border-color: var(--accent-primary);
    background: var(--bg-card-hover);
    transform: translateY(-2px);
}

/* ===== Features Grid ===== */
.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 20px;
    margin-top: 40px;
}

.feature-card {
    background: var(--bg-card);
    padding: 30px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    transition: all var(--transition-fast);
}

.feature-card:hover {
    transform: translateY(-5px);
    border-color: var(--accent-primary);
    box-shadow: 0 10px 40px var(--shadow-color);
}

.feature-card i {
    font-size: 40px;
    color: var(--accent-primary);
    margin-bottom: 15px;
}

.feature-card h3 {
    font-size: 18px;
    margin-bottom: 10px;
}

.feature-card p {
    color: var(--text-secondary);
    font-size: 14px;
}

/* ===== Course Header ===== */
.course-header {
    background: var(--bg-secondary);
    padding: 30px;
    border-radius: var(--border-radius);
    margin-bottom: 30px;
    border: 1px solid var(--border-color);
}

.course-title-section h1 {
    font-size: 28px;
    margin-bottom: 20px;
}

.progress-container {
    display: flex;
    align-items: center;
    gap: 15px;
}

.progress-bar {
    flex: 1;
    height: 12px;
    background: var(--bg-card);
    border-radius: 50px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--accent-gradient);
    border-radius: 50px;
    transition: width 0.5s ease;
    width: 0%;
}

.progress-text {
    font-weight: 600;
    color: var(--accent-primary);
    min-width: 50px;
}

/* ===== Course Content Layout ===== */
.course-content {
    display: grid;
    grid-template-columns: 1fr 320px;
    gap: 30px;
}

.course-main {
    min-width: 0;
}

/* ===== Course Sections ===== */
.course-section {
    background: var(--bg-card);
    padding: 30px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    margin-bottom: 25px;
}

.section-title {
    font-size: 22px;
    color: var(--accent-primary);
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.section-content {
    color: var(--text-secondary);
    line-height: 1.8;
}

/* ===== Lesson Cards ===== */
.lesson-card {
    background: var(--bg-card);
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    margin-bottom: 25px;
    overflow: hidden;
}

.lesson-header {
    padding: 20px 25px;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.lesson-header h3 {
    color: var(--accent-primary);
    font-size: 18px;
}

.lesson-header i {
    color: var(--text-muted);
    transition: transform var(--transition-fast);
}

.lesson-card.expanded .lesson-header i {
    transform: rotate(180deg);
}

.lesson-content {
    padding: 25px;
    display: none;
}

.lesson-card.expanded .lesson-content {
    display: block;
}

.lesson-text {
    color: var(--text-secondary);
    margin-bottom: 25px;
    line-height: 1.8;
}

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

.video-card {
    background: var(--bg-secondary);
    border-radius: var(--border-radius-sm);
    overflow: hidden;
    border: 1px solid var(--border-color);
    transition: all var(--transition-fast);
}

.video-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 10px 30px var(--shadow-color);
}

.video-thumbnail {
    position: relative;
    aspect-ratio: 16/9;
    overflow: hidden;
}

.video-thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.video-overlay {
    position: absolute;
    inset: 0;
    background: rgba(0, 0, 0, 0.4);
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: opacity var(--transition-fast);
}

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

.video-overlay i {
    font-size: 50px;
    color: white;
}

.video-info {
    padding: 15px;
}

.video-info h4 {
    font-size: 14px;
    margin-bottom: 8px;
    line-height: 1.4;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.video-meta {
    display: flex;
    gap: 10px;
    color: var(--text-muted);
    font-size: 12px;
}

.video-completed {
    position: absolute;
    top: 10px;
    right: 10px;
    background: var(--success);
    color: white;
    padding: 5px 10px;
    border-radius: 50px;
    font-size: 11px;
    font-weight: 600;
}

/* ===== Course Sidebar ===== */
.course-sidebar {
    position: sticky;
    top: calc(var(--header-height) + 30px);
    height: fit-content;
}

.sidebar-card {
    background: var(--bg-card);
    padding: 20px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    margin-bottom: 20px;
}

.sidebar-title {
    font-size: 16px;
    color: var(--accent-primary);
    margin-bottom: 15px;
    padding-bottom: 10px;
    border-bottom: 1px solid var(--border-color);
}

/* ===== Progress Checklist ===== */
.progress-checklist {
    list-style: none;
}

.progress-checklist li {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 10px 0;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 14px;
}

.progress-checklist li:last-child {
    border-bottom: none;
}

.progress-checklist li.completed {
    color: var(--success);
}

.progress-checklist li.completed i {
    color: var(--success);
}

.check-box {
    width: 20px;
    height: 20px;
    border: 2px solid var(--border-color);
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.check-box.checked {
    background: var(--accent-gradient);
    border-color: var(--accent-primary);
}

.check-box.checked::after {
    content: '✓';
    color: white;
    font-size: 12px;
    font-weight: bold;
}

/* ===== Share Buttons ===== */
.share-buttons {
    display: flex;
    gap: 10px;
}

.share-btn {
    flex: 1;
    padding: 12px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    color: var(--text-primary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.share-btn:hover {
    background: var(--bg-card-hover);
    transform: translateY(-2px);
}

/* ===== Quiz Section ===== */
.quiz-container {
    display: flex;
    flex-direction: column;
    gap: 25px;
}

.quiz-question {
    background: var(--bg-secondary);
    padding: 20px;
    border-radius: var(--border-radius-sm);
    border: 1px solid var(--border-color);
}

.quiz-question h4 {
    margin-bottom: 15px;
    font-size: 16px;
}

.quiz-options {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.quiz-option {
    padding: 12px 16px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    gap: 10px;
}

.quiz-option:hover {
    border-color: var(--accent-primary);
}

.quiz-option.selected {
    border-color: var(--accent-primary);
    background: rgba(0, 212, 170, 0.1);
}

.quiz-option.correct {
    border-color: var(--success);
    background: rgba(72, 187, 120, 0.1);
}

.quiz-option.incorrect {
    border-color: var(--danger);
    background: rgba(229, 62, 62, 0.1);
}

.quiz-option input {
    display: none;
}

.option-marker {
    width: 20px;
    height: 20px;
    border: 2px solid var(--border-color);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 12px;
    font-weight: 600;
}

.quiz-option.selected .option-marker {
    border-color: var(--accent-primary);
    background: var(--accent-primary);
    color: white;
}

.quiz-submit {
    margin-top: 20px;
}

.quiz-results {
    text-align: center;
    padding: 30px;
}

.quiz-results h3 {
    margin-bottom: 20px;
}

.score-display {
    font-size: 48px;
    font-weight: 700;
    color: var(--accent-primary);
    margin-bottom: 20px;
}

/* ===== Resources Grid ===== */
.resources-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: 15px;
}

.resource-card {
    background: var(--bg-secondary);
    padding: 20px;
    border-radius: var(--border-radius-sm);
    border: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 15px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.resource-card:hover {
    border-color: var(--accent-primary);
    transform: translateY(-2px);
}

.resource-card i {
    font-size: 24px;
    color: var(--accent-primary);
}

.resource-info h4 {
    font-size: 14px;
    margin-bottom: 4px;
}

.resource-info span {
    font-size: 12px;
    color: var(--text-muted);
}

/* ===== My Courses Page ===== */
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 25px;
}

.course-card {
    background: var(--bg-card);
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    overflow: hidden;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 15px 40px var(--shadow-color);
}

.course-card-header {
    padding: 20px;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
}

.course-card-header h3 {
    font-size: 18px;
    margin-bottom: 5px;
}

.course-card-header span {
    color: var(--text-muted);
    font-size: 13px;
}

.course-card-body {
    padding: 20px;
}

.course-card-progress {
    margin-bottom: 15px;
}

.course-card-progress .progress-bar {
    height: 8px;
    margin-bottom: 5px;
}

.course-card-progress span {
    font-size: 13px;
    color: var(--text-secondary);
}

.course-card-actions {
    display: flex;
    gap: 10px;
}

.course-card-actions button {
    flex: 1;
    padding: 10px;
    border-radius: var(--border-radius-sm);
    font-size: 13px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

/* ===== Badges Page ===== */
.badges-container {
    max-width: 1000px;
    margin: 0 auto;
}

.badges-stats {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
    margin-bottom: 40px;
}

.stat-card {
    background: var(--bg-card);
    padding: 30px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    text-align: center;
}

.stat-card i {
    font-size: 36px;
    color: var(--accent-primary);
    margin-bottom: 15px;
}

.stat-number {
    display: block;
    font-size: 36px;
    font-weight: 700;
    margin-bottom: 5px;
}

.stat-label {
    color: var(--text-secondary);
}

.badges-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 20px;
}

.badge-card {
    background: var(--bg-card);
    padding: 30px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    text-align: center;
    transition: all var(--transition-fast);
}

.badge-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px var(--shadow-color);
}

.badge-card.locked {
    opacity: 0.5;
}

.badge-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 15px;
    background: var(--accent-gradient);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.badge-icon i {
    font-size: 36px;
    color: white;
}

.badge-card.locked .badge-icon {
    background: var(--bg-secondary);
}

.badge-card.locked .badge-icon i {
    color: var(--text-muted);
}

.badge-card h4 {
    font-size: 16px;
    margin-bottom: 5px;
}

.badge-card p {
    font-size: 13px;
    color: var(--text-secondary);
}

/* ===== Settings Page ===== */
.settings-container {
    max-width: 600px;
}

.settings-section {
    background: var(--bg-card);
    padding: 25px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    margin-bottom: 20px;
}

.settings-section h3 {
    margin-bottom: 10px;
}

.settings-description {
    color: var(--text-secondary);
    font-size: 14px;
    margin-bottom: 20px;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
}

.form-group input[type="text"],
.form-group input[type="password"] {
    width: 100%;
    padding: 12px 16px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    color: var(--text-primary);
    font-size: 14px;
}

.form-group input:focus {
    outline: none;
    border-color: var(--accent-primary);
}

.help-link {
    font-size: 12px;
    display: inline-block;
    margin-top: 5px;
}

.toggle-group {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.toggle {
    position: relative;
    width: 50px;
    height: 26px;
}

.toggle input {
    opacity: 0;
    width: 0;
    height: 0;
}

.toggle-slider {
    position: absolute;
    cursor: pointer;
    inset: 0;
    background: var(--bg-secondary);
    border-radius: 26px;
    transition: var(--transition-fast);
}

.toggle-slider::before {
    content: '';
    position: absolute;
    width: 20px;
    height: 20px;
    left: 3px;
    bottom: 3px;
    background: white;
    border-radius: 50%;
    transition: var(--transition-fast);
}

.toggle input:checked + .toggle-slider {
    background: var(--accent-primary);
}

.toggle input:checked + .toggle-slider::before {
    transform: translateX(24px);
}

.danger-zone {
    border-color: var(--danger);
}

.danger-zone h3 {
    color: var(--danger);
}

/* ===== Modal ===== */
.modal {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.7);
    z-index: 2000;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.modal.active {
    display: flex;
}

.modal-content {
    background: var(--bg-card);
    border-radius: var(--border-radius);
    max-width: 500px;
    width: 100%;
    max-height: 80vh;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.modal-content.large {
    max-width: 800px;
}

.modal-header {
    padding: 20px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.modal-header h2 {
    font-size: 20px;
}

.modal-close {
    background: none;
    border: none;
    color: var(--text-primary);
    font-size: 28px;
    cursor: pointer;
    line-height: 1;
}

.modal-body {
    padding: 20px;
    overflow-y: auto;
    color: var(--text-secondary);
    line-height: 1.8;
}

/* ===== Video Modal ===== */
.video-modal-content {
    width: 90%;
    max-width: 900px;
    padding: 0;
}

.video-modal-content .modal-header {
    padding: 15px 20px;
    border-bottom: 1px solid var(--border-color);
}

.video-modal-content .modal-header h3 {
    font-size: 1rem;
    margin: 0;
    padding-right: 30px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.video-modal-content .close-btn {
    position: absolute;
    top: 10px;
    right: 15px;
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 24px;
    cursor: pointer;
    transition: color 0.2s;
}

.video-modal-content .close-btn:hover {
    color: var(--accent);
}

.video-embed-container {
    position: relative;
    padding-bottom: 56.25%;
    height: 0;
    overflow: hidden;
}

.video-embed-container iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

.video-modal-actions {
    display: flex;
    gap: 10px;
    padding: 15px 20px;
    border-top: 1px solid var(--border-color);
    justify-content: flex-end;
}

.video-modal-actions button {
    padding: 10px 20px;
    font-size: 0.9rem;
}

/* ===== Loading Overlay ===== */
.loading-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(10, 22, 40, 0.95);
    z-index: 3000;
    align-items: center;
    justify-content: center;
}

.loading-overlay.active {
    display: flex;
}

.loading-spinner {
    text-align: center;
}

.spinner {
    width: 60px;
    height: 60px;
    border: 4px solid var(--border-color);
    border-top-color: var(--accent-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 20px;
}

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

.loading-spinner p {
    font-size: 18px;
    margin-bottom: 30px;
}

.loading-steps {
    text-align: left;
    max-width: 300px;
    margin: 0 auto;
}

.loading-step {
    padding: 10px 0;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 12px;
}

.loading-step.active {
    color: var(--accent-primary);
}

.loading-step.completed {
    color: var(--success);
}

.loading-step i {
    width: 20px;
}

/* ===== Utilities ===== */
.hidden {
    display: none !important;
}

.empty-state {
    text-align: center;
    padding: 60px 20px;
    grid-column: 1 / -1;
}

.empty-state i {
    font-size: 60px;
    color: var(--text-muted);
    margin-bottom: 20px;
}

.empty-state h3 {
    margin-bottom: 10px;
    color: var(--text-secondary);
}

.empty-state p {
    color: var(--text-muted);
}

/* ===== Responsive Design ===== */
@media (max-width: 1200px) {
    .course-content {
        grid-template-columns: 1fr;
    }
    
    .course-sidebar {
        position: static;
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
        gap: 20px;
    }
    
    .sidebar-card {
        margin-bottom: 0;
    }
}

@media (max-width: 768px) {
    .sidebar {
        transform: translateX(-100%);
    }
    
    .sidebar.active {
        transform: translateX(0);
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .menu-toggle {
        display: block;
    }
    
    .header {
        padding: 0 15px;
    }
    
    .search-container {
        flex-direction: column;
    }
    
    .hero-section h1 {
        font-size: 32px;
    }
    
    .page {
        padding: 20px;
    }
    
    .course-header {
        padding: 20px;
    }
    
    .course-title-section h1 {
        font-size: 22px;
    }
    
    .video-grid {
        grid-template-columns: 1fr;
    }
    
    .badges-stats {
        grid-template-columns: 1fr;
    }
}

/* ===== User Profile Styles ===== */
.profile-container {
    position: relative;
}

.profile-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
    border-radius: 50%;
    transition: all var(--transition-fast);
}

.profile-btn:hover {
    background: var(--bg-card);
}

.profile-avatar {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--accent-gradient);
    color: white;
    font-weight: 600;
    font-size: 14px;
    overflow: hidden;
}

.profile-avatar.empty {
    background: var(--bg-card);
    border: 2px dashed var(--border-color);
    color: var(--text-muted);
}

.profile-avatar.guest {
    background: var(--bg-card);
    border: 2px solid var(--warning);
    color: var(--warning);
}

.profile-avatar.large {
    width: 56px;
    height: 56px;
    font-size: 18px;
}

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

.profile-initials {
    font-size: inherit;
}

.profile-dropdown {
    position: absolute;
    top: calc(100% + 10px);
    right: 0;
    width: 280px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    box-shadow: 0 10px 40px var(--shadow-color);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all var(--transition-fast);
    z-index: 1001;
}

.profile-dropdown.active {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.profile-info {
    padding: 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    border-bottom: 1px solid var(--border-color);
}

.profile-details {
    margin-top: 12px;
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.profile-name {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 16px;
}

.profile-email {
    font-size: 13px;
    color: var(--text-secondary);
}

.profile-badge {
    display: inline-block;
    padding: 4px 10px;
    background: var(--accent-primary);
    color: white;
    border-radius: 20px;
    font-size: 11px;
    font-weight: 600;
    margin-top: 6px;
}

.profile-badge.guest {
    background: var(--warning);
}

.profile-message {
    color: var(--text-secondary);
    font-size: 14px;
    line-height: 1.5;
}

.profile-warning {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 12px 16px;
    background: rgba(237, 137, 54, 0.1);
    color: var(--warning);
    font-size: 12px;
    border-bottom: 1px solid var(--border-color);
}

.profile-warning i {
    font-size: 14px;
}

.profile-action {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    width: 100%;
    padding: 14px 20px;
    background: none;
    border: none;
    border-top: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 14px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.profile-action:first-of-type {
    border-top: none;
}

.profile-action:hover {
    background: var(--bg-card);
    color: var(--text-primary);
}

.profile-action.primary {
    background: var(--accent-gradient);
    color: white;
    border-radius: 0 0 var(--border-radius) var(--border-radius);
}

.profile-action.primary:hover {
    opacity: 0.9;
}

/* ===== Auth Modal Styles ===== */
.auth-modal .modal-content {
    max-width: 420px;
}

.auth-modal .modal-header {
    text-align: center;
    padding-bottom: 10px;
}

.auth-modal .modal-header h2 {
    font-size: 24px;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.auth-subtitle {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 24px;
    font-size: 14px;
}

.auth-error {
    display: none;
    padding: 12px 16px;
    background: rgba(229, 62, 62, 0.1);
    border: 1px solid var(--danger);
    border-radius: var(--border-radius-sm);
    color: var(--danger);
    font-size: 13px;
    margin-bottom: 16px;
    text-align: center;
}

.auth-error.active {
    display: block;
}

.auth-buttons {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.auth-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    width: 100%;
    padding: 14px 20px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    background: var(--bg-card);
    color: var(--text-primary);
    font-size: 15px;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.auth-btn:hover {
    background: var(--bg-card-hover);
    border-color: var(--text-muted);
    transform: translateY(-1px);
}

.auth-btn.google:hover {
    border-color: #4285F4;
    box-shadow: 0 4px 12px rgba(66, 133, 244, 0.2);
}

.auth-btn.microsoft:hover {
    border-color: #00A4EF;
    box-shadow: 0 4px 12px rgba(0, 164, 239, 0.2);
}

.auth-btn.guest {
    background: transparent;
    border-style: dashed;
    color: var(--text-secondary);
}

.auth-btn.guest:hover {
    border-color: var(--accent-primary);
    color: var(--accent-primary);
}

.auth-btn svg,
.auth-btn i {
    flex-shrink: 0;
}

.auth-divider {
    display: flex;
    align-items: center;
    margin: 24px 0;
    color: var(--text-muted);
    font-size: 13px;
}

.auth-divider::before,
.auth-divider::after {
    content: '';
    flex: 1;
    height: 1px;
    background: var(--border-color);
}

.auth-divider span {
    padding: 0 16px;
}

.auth-guest-note {
    display: flex;
    align-items: flex-start;
    gap: 8px;
    margin-top: 16px;
    padding: 12px;
    background: rgba(237, 137, 54, 0.1);
    border-radius: var(--border-radius-sm);
    color: var(--warning);
    font-size: 12px;
    line-height: 1.5;
}

.auth-guest-note i {
    margin-top: 2px;
    flex-shrink: 0;
}

/* ===== Auth Notification ===== */
.auth-notification {
    position: fixed;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 14px 24px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    box-shadow: 0 10px 40px var(--shadow-color);
    color: var(--text-primary);
    font-size: 14px;
    z-index: 2000;
    opacity: 0;
    transition: all 0.3s ease;
}

.auth-notification.active {
    transform: translateX(-50%) translateY(0);
    opacity: 1;
}

.auth-notification.success i {
    color: var(--success);
}

.auth-notification.error i {
    color: var(--danger);
}

/* ===== Print Styles ===== */
@media print {
    .sidebar,
    .header,
    .course-sidebar,
    .video-grid,
    .quiz-section {
        display: none !important;
    }
    
    .main-content {
        margin-left: 0;
    }
    
    .course-content {
        display: block;
    }
}