/* ============================================
   CSS VARIABLES
   ============================================ */
:root {
    /* Brand Colors */
    --color-primary: #8b5cf6;
    --color-primary-dark: #7c3aed;
    --color-primary-light: #a78bfa;
    --color-success: #10b981;
    --color-error: #ef4444;
    --color-warning: #f59e0b;
    
    /* Text Colors */
    --text-primary: #2C3E50;
    --text-secondary: #64748b;
    --text-primary-dark: #e2e8f0;
    --text-secondary-dark: #94a3b8;
    
    /* Backgrounds */
    --bg-light: #f8fafc;
    --bg-dark: #1a1625;
    --bg-code-light: white;
    --bg-code-dark: #0f172a;
    
    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #8b5cf6 0%, #7c3aed 100%);
    --gradient-success: linear-gradient(135deg, #10b981 0%, #059669 100%);
    --gradient-background: linear-gradient(135deg, #f5f3ff 0%, #ede9fe 100%);
    --gradient-background-dark: linear-gradient(135deg, #1e1b4b 0%, #312e81 100%);
    
    /* Effects */
    --transition-standard: all 0.2s;
    --transition-slow: all 0.3s;
    --shadow-purple: 0 2px 8px rgba(139, 92, 246, 0.1);
    --shadow-purple-lg: 0 4px 12px rgba(139, 92, 246, 0.3);
    --shadow-dark: 0 4px 16px rgba(0, 0, 0, 0.3);
    
    /* Spacing */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
}


/* ============================================
   MAIN.CSS - Base Styles, Layout & Navigation
   ============================================ */

* { margin: 0; padding: 0; box-sizing: border-box; }

body { 
    font-family: 'Atkinson Hyperlegible', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    text-rendering: optimizeLegibility;
    background: var(--gradient-background);
    height: 100vh; 
    display: flex; 
    flex-direction: column; 
    overflow: hidden;
}

/* ============================================
   HEADER
   ============================================*/
.header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 70px;
    background: rgba(255, 255, 255, 0.95);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 var(--radius-xl);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05);
    z-index: 100;
    backdrop-filter: blur(4px);
    border-bottom: 1px solid #e2e8f0;
}

.title {
    font-size: 24px;
    font-weight: 700;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 15px;
}

.python-badge {
    display: inline-block;
    background: rgba(139, 92, 246, 0.1);
    color: var(--color-primary-dark);
    padding: 6px 14px;
    border-radius: var(--radius-lg);
    font-size: 14px;
    font-weight: 600;
    border: 1px solid rgba(139, 92, 246, 0.2);
}

.status-indicator {
    display: inline-block;
    padding: 6px 14px;
    border-radius: var(--radius-lg);
    font-size: 14px;
    font-weight: 600;
    margin-right: 10px;
}

.status-ready {
    background: rgba(16, 185, 129, 0.1);
    color: var(--color-success);
    border: 1px solid rgba(16, 185, 129, 0.2);
}

.status-loading {
    background: rgba(251, 191, 36, 0.1);
    color: var(--color-warning);
    border: 1px solid rgba(251, 191, 36, 0.2);
}

/* ============================================
   HAMBURGER MENU
   ============================================ */
.menu-btn {
    font-size: 24px;
    cursor: pointer;
    padding: 5px 10px;
    border-radius: 6px;
    background: #f1f5f9;
    color: var(--text-primary);
    transition: var(--transition-standard);
}

.menu-btn:hover {
    background: #e2e8f0;
    color: var(--color-primary);
}

.menu-panel {
    position: fixed;
    left: -320px;
    top: 0;
    width: 300px;
    height: 100vh;
    background: rgba(255, 255, 255, 0.98);
    backdrop-filter: blur(10px);
    box-shadow: 2px 0 20px rgba(139, 92, 246, 0.15);
    transition: left 0.3s ease;
    z-index: 1000;
    padding: 2rem;
}

.menu-panel.active {
    left: 0;
}

.menu-header {
    font-size: 22px;
    font-weight: 600;
    color: #5b21b6;
    margin-bottom: 1.5rem;
    padding-bottom: 1rem;
    border-bottom: 2px solid #ede9fe;
}

.menu-item {
    padding: 14px 18px;
    margin: 10px 0;
    border-radius: 10px;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 12px;
    color: var(--text-primary);
    text-decoration: none;
    transition: var(--transition-standard);
    font-size: 18px;
}

.menu-item:hover {
    background: #f5f3ff;
    color: var(--color-primary-dark);
}

.menu-item.active {
    background: rgba(139, 92, 246, 0.1);
    color: var(--color-primary);
    border-left: 4px solid var(--color-primary);
    padding-left: 14px; /* Adjust padding for border */
}

.menu-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.4);
    display: none;
    z-index: 999;
}

.menu-overlay.active {
    display: block;
}

/* ============================================
   LESSONS & CHALLENGES LAYOUT
   ============================================ */
/* ============================================
   PAGE LAYOUT SYSTEM
   ============================================
   Each page mode has a specific grid structure:
   - Challenges: 3 columns (sidebar, content, ads)
   - Lessons: 2 columns (content, ads)
   - IDE: 1 column (full width, internal 2-col grid)
   - AI Tutor: 2 columns (content, ads)
   - GCSE: 1 column (full width content)
   ============================================ */

/* Three-column layout: Sidebar + Content + Ads */
.challenges-page-grid {
    display: grid;
    grid-template-columns: 300px 1fr 300px;
    flex-grow: 1;
    padding-top: 70px;
    overflow: hidden;
}

/* Two-column layout: Content + Ads (no sidebar) */
.lessons-page-grid,
.ai-tutor-grid {
    display: grid;
    grid-template-columns: 1fr 300px;
    flex-grow: 1;
    padding-top: 70px;
    overflow: hidden;
}

/* Single-column layout: Full width */
.ide-page-grid,
.gcse-page-grid {
    display: grid;
    grid-template-columns: 1fr;
    flex-grow: 1;
    padding-top: 70px;
    overflow: hidden;
}

/* Content Area (1fr) */
.lessons-content,
.gcse-content,
.ide-content,
.ai-content {
    padding: 30px;
    overflow-y: auto;
}

/* Ad Column (300px) */
.ad-column {
    padding: 30px 30px 30px 0;
    overflow-y: auto;
}

/* Sidebar (300px) */
.lesson-sidebar {
    padding: 30px 0 30px 30px;
    overflow-y: auto;
}

/* ============================================
   AD SPACE
   ============================================ */
.partner-box {
    background: var(--bg-light);
    border: 2px dashed #cbd5e1;
    border-radius: var(--radius-lg);
    padding: 30px;
    text-align: center;
    margin-bottom: 20px;
}

.partner-box span {
    display: block;
    color: var(--text-secondary);
    font-size: 16px;
    font-weight: 500;
}

.partner-box span:first-child {
    font-size: 32px;
    margin-bottom: 10px;
}

/* ============================================
   GENERAL CONTENT STYLING
   ============================================ */
.lessons-header {
    margin-bottom: 30px;
}

.lessons-header h2 {
    font-size: 32px;
    color: var(--text-primary);
    margin-bottom: 10px;
}

.lessons-header p {
    font-size: 18px;
    color: var(--text-secondary);
}

/* ============================================
   FILTERS
   ============================================ */
.filter-section {
    margin-bottom: 30px;
    padding-bottom: 20px;
    border-bottom: 1px solid #e2e8f0;
}

.filter-title {
    font-size: 20px;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 15px;
}

.filter-buttons {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.filter-btn {
    background: var(--bg-code-light);
    color: var(--text-secondary);
    border: 1px solid #cbd5e1;
    padding: 8px 16px;
    border-radius: var(--radius-xl);
    font-size: 14px;
    cursor: pointer;
    transition: var(--transition-standard);
}

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

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

/* ============================================
   LESSON CARDS GRID
   ============================================ */
.lesson-cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
}

.lesson-card {
    background: var(--bg-code-light);
    border-radius: var(--radius-lg);
    padding: 24px;
    box-shadow: var(--shadow-purple);
    transition: var(--transition-standard);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    border: 1px solid #ede9fe;
}

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

.lesson-card h3 {
    font-size: 20px;
    color: var(--text-primary);
    margin-bottom: 10px;
    font-weight: 600;
}

.lesson-card p {
    color: var(--text-secondary);
    line-height: 1.5;
    margin-bottom: 15px;
    flex-grow: 1;
}

.lesson-card-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 15px;
    border-top: 1px solid #e2e8f0;
}

.lesson-card-footer div {
    display: flex;
    gap: 8px;
}

.lesson-card-footer span {
    display: inline-block;
    padding: 4px 10px;
    border-radius: var(--radius-md);
    font-size: 12px;
    font-weight: 600;
}

.lesson-category {
    background: rgba(139, 92, 246, 0.1);
    color: var(--color-primary-dark);
}

.lesson-difficulty {
    background: #e2e8f0;
    color: #64748b;
}

.lesson-card.completed {
    border-left: 5px solid var(--color-success);
    opacity: 0.9;
}

.lesson-card.completed:hover {
    border-left-color: var(--color-primary);
}

.lesson-link {
    color: var(--color-primary);
    text-decoration: none;
    font-weight: 600;
    cursor: pointer;
}

.lesson-link:hover {
    text-decoration: underline;
}

.lesson-link.new {
    background: var(--gradient-success);
    color: white;
    padding: 5px 10px;
    border-radius: 6px;
    font-size: 14px;
    font-weight: 700;
    text-decoration: none;
    margin-left: 10px;
}

/* ============================================
   PROGRESS BAR
   ============================================ */
.progress-bar {
    padding: 1rem 0;
    margin-top: 1.5rem;
    border-top: 1px solid #e2e8f0;
}

.progress-label {
    font-size: 16px;
    color: var(--text-secondary);
    margin-bottom: 8px;
}

.progress-track {
    height: 10px;
    background: #ede9fe;
    border-radius: 5px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--color-primary), var(--color-success));
    transition: var(--transition-slow);
}

/* ============================================
   RESPONSIVE BREAKPOINTS
   ============================================ */
@media (max-width: 1024px) {
    .lessons-page-grid,
    .challenges-page-grid,
    .ide-page-grid,
    .ai-tutor-grid,
    .gcse-page-grid {
        grid-template-columns: 1fr; /* Stack on smaller screens */
    }

    .lesson-sidebar {
        padding: var(--radius-xl) var(--radius-xl) 0 var(--radius-xl);
        overflow-y: visible;
    }

    .ad-column {
        padding: var(--radius-xl);
        border-top: 1px solid #e2e8f0;
        overflow-y: visible;
    }

    .lessons-content,
    .gcse-content,
    .ide-content,
    .ai-content {
        padding: 30px;
    }

    .lessons-header {
        margin-bottom: var(--radius-xl);
    }
}

@media (max-width: 600px) {
    .header {
        height: 60px;
        padding: 0 15px;
    }

    .title {
        font-size: 20px;
    }

    .menu-panel {
        width: 250px;
    }

    .lessons-page-grid,
    .challenges-page-grid,
    .ide-page-grid,
    .ai-tutor-grid,
    .gcse-page-grid {
        padding-top: 60px;
    }

    .lessons-content,
    .gcse-content,
    .ide-content,
    .ai-content {
        padding: 15px;
    }

    .lesson-sidebar {
        padding: 15px 15px 0 15px;
    }

    .ad-column {
        padding: 15px;
    }
}