:root {
    --primary-color: #4a6fa5;
    --primary-light: #6b8cb8;
    --primary-dark: #345689;
    --secondary-color: #ff7e5f;
    --secondary-light: #ff9a85;
    --secondary-dark: #e65c3e;
    --accent-color: #5cb85c;
    --accent-light: #78c578;
    --accent-dark: #449d44;
    --text-color: #333;
    --text-light: #666;
    --text-dark: #111;
    --background-color: #f8f9fa;
    --background-light: #ffffff;
    --background-dark: #e9ecef;
    --border-color: #dee2e6;
    --border-radius: 8px;
    --box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s ease;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    margin: 0;
    padding: 0;
    line-height: 1.6;
}

/* Header Styles */
.header {
    background-color: var(--accent-color);
    padding: 15px 30px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
}

.logo img {
    height: 40px;
    width: auto;
}

.logo h1 {
    color: white;
    margin: 0;
    font-size: 1.5rem;
}

.nav ul {
    display: flex;
    list-style: none;
    margin: 0;
    padding: 0;
    gap: 20px;
}

.nav-link {
    color: white;
    text-decoration: none;
    font-weight: 500;
    padding: 5px 10px;
    border-radius: var(--border-radius);
    transition: var(--transition);
}

.nav-link:hover {
    background-color: rgba(255, 255, 255, 0.2);
}

.nav-link.active {
    background-color: white;
    color: var(--accent-color);
}

/* Learning Container Layout */
.learning-container {
    display: flex;
    max-width: 1400px;
    margin: 20px auto;
    background-color: var(--background-light);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    overflow: hidden;
}

/* Sidebar Styles */
.sidebar {
    width: 280px;
    background-color: var(--primary-dark);
    color: white;
    padding: 20px;
    flex-shrink: 0;
}

.course-levels, .categories {
    margin-bottom: 30px;
}

.sidebar h3 {
    font-size: 1.2rem;
    margin-bottom: 15px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.2);
    padding-bottom: 10px;
}

.level-list, .category-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.level, .category {
    padding: 10px 15px;
    margin-bottom: 8px;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: var(--transition);
    background-color: rgba(255, 255, 255, 0.1);
}

.level:hover, .category:hover {
    background-color: rgba(255, 255, 255, 0.2);
}

.level.active, .category.active {
    background-color: var(--secondary-color);
    font-weight: 500;
}

.progress-bar {
    height: 6px;
    background-color: rgba(255, 255, 255, 0.2);
    border-radius: 3px;
    margin-top: 8px;
    overflow: hidden;
}

.progress {
    height: 100%;
    background-color: var(--accent-color);
    border-radius: 3px;
}

/* Content Area Styles */
.content-area {
    flex-grow: 1;
    padding: 30px;
    overflow-y: auto;
}

.level-content {
    display: none;
}

.level-content.active {
    display: block;
    animation: fadeIn 0.5s ease;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.level-header {
    margin-bottom: 30px;
}

.level-header h2 {
    font-size: 2rem;
    color: var(--primary-dark);
    margin-bottom: 10px;
}

.level-header p {
    color: var(--text-light);
    font-size: 1.1rem;
}

/* Lessons Grid */
.lessons-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 25px;
}

/* Lesson Card Styles */
.lesson-card {
    display: flex;
    flex-direction: column;
    background-color: var(--background-light);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    transition: var(--transition);
    border: 1px solid var(--border-color);
}

.lesson-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 15px rgba(0, 0, 0, 0.1);
}

.lesson-thumbnail {
    position: relative;
    height: 160px;
    overflow: hidden;
}

.lesson-thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: var(--transition);
}

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

.completion-badge {
    position: absolute;
    top: 10px;
    right: 10px;
    background-color: var(--accent-color);
    color: white;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
}

.progress-indicator {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    background-color: rgba(0, 0, 0, 0.7);
    color: white;
    text-align: center;
    padding: 5px;
    font-size: 14px;
    font-weight: 500;
}

.lock-indicator {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 24px;
}

.lesson-info {
    padding: 20px;
    flex-grow: 1;
    display: flex;
    flex-direction: column;
}

.lesson-info h3 {
    margin: 0 0 10px 0;
    font-size: 1.2rem;
    color: var(--primary-dark);
}

.lesson-info p {
    margin: 0 0 15px 0;
    color: var(--text-light);
    font-size: 0.95rem;
}

.lesson-meta {
    display: flex;
    justify-content: space-between;
    margin-bottom: 15px;
    color: var(--text-light);
    font-size: 0.85rem;
}

/* Button Styles */
.btn {
    display: inline-block;
    padding: 8px 16px;
    border-radius: var(--border-radius);
    font-weight: 500;
    text-align: center;
    cursor: pointer;
    transition: var(--transition);
    border: none;
    text-decoration: none;
    margin-top: auto;
}

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

.btn-primary:hover {
    background-color: var(--primary-dark);
}

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

.btn-secondary:hover {
    background-color: var(--secondary-dark);
}

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

.btn-accent:hover {
    background-color: var(--accent-dark);
}

.btn-disabled {
    background-color: var(--border-color);
    color: var(--text-light);
    cursor: not-allowed;
}

/* Status-specific styles */
.lesson-card.completed .lesson-info h3 {
    color: var(--accent-color);
}

.lesson-card.in-progress .lesson-info h3 {
    color: var(--secondary-color);
}

.lesson-card.locked {
    opacity: 0.8;
}

.lesson-card.locked .lesson-info h3 {
    color: var(--text-light);
}

/* Responsive Design */
@media (max-width: 992px) {
    .learning-container {
        flex-direction: column;
        margin: 10px;
    }
    
    .sidebar {
        width: 100%;
        padding: 15px;
    }
    
    .content-area {
        padding: 20px;
    }
    
    .lessons-grid {
        grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
        gap: 15px;
    }
}

@media (max-width: 576px) {
    .lessons-grid {
        grid-template-columns: 1fr;
    }
    
    .level-header h2 {
        font-size: 1.5rem;
    }
    
    .level-header p {
        font-size: 1rem;
    }
}