/* ============================================
   Claude Code Academy - Beautiful Styles
   Split-Screen Learning Experience
   ============================================ */

/* ============================================
   CSS Variables - Design System
   ============================================ */
:root {
    /* Colors - Dark Theme (Default) - Networking & Security Theme */
    --bg-primary: #0d1117;
    --bg-secondary: #161b22;
    --bg-tertiary: #21262d;
    --bg-elevated: #1c2128;

    --text-primary: #e6edf3;
    --text-secondary: #c9d1d9;
    --text-body: #b6c2cc;
    --text-tertiary: #6e7681;

    /* Networking & Security Accent Colors */
    --accent-primary: #00d4aa;
    --accent-secondary: #6366f1;
    --accent-hover: #00ffcc;
    --accent-networking: #00d4aa;
    --accent-security: #6366f1;

    --border-primary: #30363d;
    --border-secondary: #21262d;

    --success: #3fb950;
    --warning: #d29922;
    --error: #f85149;
    --info: #00d4aa;

    /* Gradients - Networking & Security Theme */
    --gradient-primary: linear-gradient(135deg, #00d4aa 0%, #6366f1 100%);
    --gradient-networking: linear-gradient(135deg, #00d4aa 0%, #00a896 100%);
    --gradient-security: linear-gradient(135deg, #6366f1 0%, #4f46e5 100%);
    --gradient-accent: linear-gradient(135deg, #00d4aa 0%, #6366f1 100%);
    --gradient-success: linear-gradient(135deg, #3fb950 0%, #2ea043 100%);

    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.5);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.6);

    /* Typography */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', 'Courier New', monospace;

    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 350ms ease;

    /* Layout */
    --header-height: 64px;
    --sidebar-width: 320px;
    --border-radius-sm: 4px;
    --border-radius-md: 8px;
    --border-radius-lg: 12px;
}

/* Light Theme - Networking & Security */
body.light-theme {
    --bg-primary: #ffffff;
    --bg-secondary: #f6f8fa;
    --bg-tertiary: #eaeef2;
    --bg-elevated: #ffffff;

    --text-primary: #24292f;
    --text-secondary: #57606a;
    --text-tertiary: #6e7781;

    --accent-primary: #00a896;
    --accent-secondary: #4f46e5;
    --accent-hover: #00c4a8;
    --accent-networking: #00a896;
    --accent-security: #4f46e5;

    --border-primary: #d0d7de;
    --border-secondary: #eaeef2;

    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.07);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.15);
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ============================================
   Header
   ============================================ */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-primary);
    z-index: 1000;
    box-shadow: var(--shadow-md);
}

.header-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
    padding: 0 var(--spacing-xl);
    max-width: 100%;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    cursor: pointer;
    transition: transform var(--transition-base);
}

.logo:hover {
    transform: scale(1.05);
}

.logo i {
    font-size: 1.5rem;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* Main Navigation */
.main-nav {
    display: flex;
    gap: var(--spacing-sm);
}

.nav-btn {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-lg);
    background: transparent;
    border: none;
    border-radius: var(--border-radius-md);
    color: var(--text-secondary);
    font-family: var(--font-primary);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-base);
}

.nav-btn:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

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

/* Header Actions */
.header-actions {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.btn-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background: transparent;
    border: none;
    border-radius: var(--border-radius-md);
    color: var(--text-secondary);
    font-size: 1.1rem;
    cursor: pointer;
    transition: all var(--transition-base);
    position: relative;
}

.btn-icon:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
    transform: translateY(-2px);
}

.btn-icon.success {
    background: var(--success) !important;
    color: white !important;
}

/* Copy Button Feedback */
.btn-icon.copied::after {
    content: 'Copied!';
    position: absolute;
    top: -30px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--success);
    color: white;
    padding: 4px 8px;
    border-radius: var(--border-radius-sm);
    font-size: 0.75rem;
    white-space: nowrap;
    animation: fadeInOut 2s;
}

@keyframes fadeInOut {
    0%, 100% { opacity: 0; }
    10%, 90% { opacity: 1; }
}

/* Tooltip */
.btn-icon[title]:hover::before {
    content: attr(title);
    position: absolute;
    bottom: -35px;
    left: 50%;
    transform: translateX(-50%);
    background: var(--bg-elevated);
    color: var(--text-primary);
    padding: 6px 10px;
    border-radius: var(--border-radius-sm);
    font-size: 0.75rem;
    white-space: nowrap;
    z-index: 100;
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-primary);
}

/* ============================================
   Main Container
   ============================================ */
.main-container {
    display: flex;
    margin-top: var(--header-height);
    height: calc(100vh - var(--header-height));
    overflow: hidden;
}

/* ============================================
   Sidebar
   ============================================ */
.sidebar {
    width: var(--sidebar-width);
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-primary);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    transition: transform var(--transition-base);
}

.sidebar.collapsed {
    transform: translateX(-100%);
}

.sidebar-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-lg);
    border-bottom: 1px solid var(--border-primary);
}

.sidebar-header h3 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
}

/* Search Box */
.search-box {
    position: relative;
    padding: var(--spacing-md) var(--spacing-lg);
}

.search-box i {
    position: absolute;
    left: calc(var(--spacing-lg) + var(--spacing-md));
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-tertiary);
}

.search-box input {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-sm) var(--spacing-sm) var(--spacing-2xl);
    background: var(--bg-tertiary);
    border: 1px solid var(--border-primary);
    border-radius: var(--border-radius-md);
    color: var(--text-primary);
    font-family: var(--font-primary);
    font-size: 0.9rem;
    transition: all var(--transition-base);
}

.search-box input:focus {
    outline: none;
    border-color: var(--accent-primary);
    background: var(--bg-primary);
    box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.1);
}

/* Progress Overview - Enhanced */
.progress-overview {
    padding: var(--spacing-md) var(--spacing-lg);
    border-bottom: 1px solid var(--border-primary);
}

.progress-label {
    display: flex;
    justify-content: space-between;
    margin-bottom: var(--spacing-sm);
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.progress-percent {
    font-weight: 600;
    color: var(--accent-primary);
}

.progress-bar {
    height: 8px;
    background: var(--bg-tertiary);
    border-radius: 999px;
    overflow: hidden;
    position: relative;
}

.progress-fill {
    height: 100%;
    background: var(--gradient-primary);
    border-radius: 999px;
    transition: width var(--transition-slow);
    position: relative;
    overflow: hidden;
}

.progress-fill::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
    background: linear-gradient(
        90deg,
        transparent,
        rgba(255, 255, 255, 0.3),
        transparent
    );
    animation: shimmer 2s infinite;
}

@keyframes shimmer {
    0% { transform: translateX(-100%); }
    100% { transform: translateX(100%); }
}

/* Continue Learning Section */
.continue-learning {
    padding: var(--spacing-md) var(--spacing-lg);
    background: linear-gradient(135deg, rgba(0, 212, 170, 0.1) 0%, rgba(99, 102, 241, 0.1) 100%);
    border-bottom: 1px solid var(--border-primary);
    border-left: 3px solid var(--accent-primary);
    margin: var(--spacing-md);
    border-radius: var(--border-radius-md);
    cursor: pointer;
    transition: all var(--transition-base);
}

.continue-learning:hover {
    background: linear-gradient(135deg, rgba(0, 212, 170, 0.15) 0%, rgba(99, 102, 241, 0.15) 100%);
    transform: translateX(4px);
}

.continue-title {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-tertiary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: var(--spacing-xs);
}

.continue-chapter {
    font-size: 0.9rem;
    color: var(--text-primary);
    margin-bottom: var(--spacing-xs);
}

.continue-progress {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 0.75rem;
    color: var(--accent-primary);
}

/* Sidebar Navigation */
.sidebar-nav {
    flex: 1;
    overflow-y: auto;
    padding: var(--spacing-md) 0;
}

/* Volume Groups - Enhanced with Collapse/Expand */
.module-group {
    margin-bottom: var(--spacing-md);
}

.module-group-title {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-md) var(--spacing-lg);
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-primary);
    text-transform: none;
    letter-spacing: 0.3px;
    background: var(--bg-tertiary);
    cursor: pointer;
    border-radius: var(--border-radius-sm);
    transition: all var(--transition-base);
    margin-bottom: var(--spacing-sm);
}

.module-group-title:hover {
    background: var(--bg-elevated);
    color: var(--accent-primary);
}

.volume-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    flex: 1;
}

.volume-icon {
    font-size: 1rem;
    color: var(--accent-primary);
}

.volume-title {
    flex: 1;
}

.volume-stats {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    font-size: 0.75rem;
    color: var(--text-tertiary);
}

.volume-progress-badge {
    padding: 2px 8px;
    background: var(--gradient-primary);
    border-radius: var(--border-radius-sm);
    color: white;
    font-weight: 600;
}

.collapse-icon {
    font-size: 0.9rem;
    transition: transform var(--transition-base);
    color: var(--text-secondary);
}

.module-group.collapsed .collapse-icon {
    transform: rotate(-90deg);
}

.module-group.collapsed .module-list {
    display: none;
}

.module-list {
    padding-left: var(--spacing-sm);
}

/* Chapter Items - Enhanced */
.module-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    padding: var(--spacing-md) var(--spacing-lg);
    color: var(--text-secondary);
    text-decoration: none;
    transition: all var(--transition-base);
    cursor: pointer;
    border-left: 3px solid transparent;
    position: relative;
}

.module-item:hover {
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border-left-color: var(--accent-primary);
}

.module-item.active {
    background: var(--bg-elevated);
    color: var(--accent-primary);
    border-left-color: var(--accent-primary);
    font-weight: 500;
}

.module-item.completed {
    color: var(--success);
}

.module-item.completed .module-icon {
    color: var(--success);
}

.chapter-number {
    min-width: 30px;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-tertiary);
    text-align: center;
}

.module-icon {
    width: 20px;
    text-align: center;
    font-size: 0.9rem;
}

.module-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.module-title {
    font-size: 0.9rem;
    line-height: 1.3;
}

.module-meta {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 0.75rem;
    color: var(--text-tertiary);
}

.time-estimate {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.module-badge {
    padding: 2px 6px;
    background: var(--accent-primary);
    border-radius: var(--border-radius-sm);
    font-size: 0.7rem;
    font-weight: 600;
    color: white;
}

.notebook-badge {
    background: var(--gradient-primary);
}

.completed-badge {
    background: var(--success);
}

/* ============================================
   Content Wrapper (Split Screen)
   ============================================ */
.content-wrapper {
    flex: 1;
    display: flex;
    overflow: hidden;
    position: relative;
}

/* ============================================
   Panels (Left & Right)
   ============================================ */
.panel {
    display: flex;
    flex-direction: column;
    background: var(--bg-primary);
    overflow: hidden;
}

.panel-left {
    flex: 1;
    min-width: 300px;
}

.panel-right {
    flex: 1;
    min-width: 300px;
    background: var(--bg-secondary);
}

/* Panel Header */
.panel-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-lg);
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-primary);
}

.panel-title {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
}

.panel-title i {
    color: var(--accent-primary);
}

.panel-actions {
    display: flex;
    gap: var(--spacing-sm);
}

/* Panel Content */
.panel-content {
    flex: 1;
    padding: var(--spacing-2xl);
    overflow-y: auto;
    line-height: 1.8;
}

.panel-content h1 {
    font-size: 2rem;
    margin-bottom: var(--spacing-lg);
    color: var(--text-primary);
    line-height: 1.2;
}

.panel-content h2 {
    font-size: 1.45rem;
    font-weight: 700;
    margin-top: var(--spacing-2xl);
    margin-bottom: var(--spacing-md);
    color: #e6edf3;
    border-bottom: 1px solid rgba(99,102,241,0.3);
    padding-bottom: var(--spacing-sm);
    letter-spacing: -0.01em;
}

.panel-content h3 {
    font-size: 1.15rem;
    font-weight: 600;
    margin-top: var(--spacing-xl);
    margin-bottom: var(--spacing-md);
    color: #c9d1d9;
    letter-spacing: -0.01em;
}

.panel-content p {
    margin-bottom: var(--spacing-md);
    color: var(--text-secondary);
    font-size: 0.97rem;
    line-height: 1.85;
}

.panel-content ul,
.panel-content ol {
    margin-bottom: var(--spacing-md);
    padding-left: var(--spacing-xl);
}

.panel-content li {
    margin-bottom: 0.5rem;
    color: var(--text-secondary);
    font-size: 0.97rem;
    line-height: 1.75;
}

.panel-content ul li::marker {
    color: var(--accent-primary);
    font-size: 1.1em;
}

.panel-content ol li::marker {
    color: var(--accent-primary);
    font-weight: 600;
}

.panel-content code {
    padding: 2px 8px;
    background: rgba(99,102,241,0.12);
    border: 1px solid rgba(99,102,241,0.2);
    border-radius: 5px;
    font-family: var(--font-mono);
    font-size: 0.88em;
    color: #a5b4fc;
}

.panel-content pre {
    margin: var(--spacing-lg) 0;
    padding: var(--spacing-lg);
    background: #0d1117;
    border-radius: 10px;
    border: 1px solid rgba(99,102,241,0.2);
    border-left: 3px solid #6366f1;
    overflow-x: auto;
    font-size: 0.875rem;
    line-height: 1.7;
}

.panel-content pre code {
    padding: 0;
    background: transparent;
    color: var(--text-primary);
}

.panel-content blockquote {
    margin: var(--spacing-lg) 0;
    padding: 14px 20px;
    border-left: 3px solid #6366f1;
    background: rgba(99,102,241,0.06);
    border-radius: 0 8px 8px 0;
    color: #b6c2cc;
    font-style: italic;
    font-size: 0.95rem;
    line-height: 1.75;
}

/* Panel Footer - Enhanced */
.panel-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-lg);
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-primary);
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

.footer-left {
    display: flex;
    gap: var(--spacing-sm);
}

.footer-right {
    display: flex;
    gap: var(--spacing-sm);
}

/* Buttons */
.btn {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) var(--spacing-lg);
    border: none;
    border-radius: var(--border-radius-md);
    font-family: var(--font-primary);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-base);
}

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

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

.btn-secondary {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.btn-secondary:hover {
    background: var(--bg-elevated);
}

/* ============================================
   Resizer
   ============================================ */
.resizer {
    width: 8px;
    background: var(--bg-tertiary);
    cursor: col-resize;
    position: relative;
    transition: background var(--transition-base);
}

.resizer:hover {
    background: var(--accent-primary);
}

.resizer::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 3px;
    height: 40px;
    background: var(--border-primary);
    border-radius: 999px;
}

.resizer:hover::before {
    background: white;
}

/* ============================================
   Code Panel
   ============================================ */
.code-editor-wrapper {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

/* Code Tabs */
.code-tabs {
    display: flex;
    background: var(--bg-tertiary);
    border-bottom: 1px solid var(--border-primary);
}

.code-tab {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) var(--spacing-lg);
    background: transparent;
    border: none;
    border-bottom: 2px solid transparent;
    color: var(--text-secondary);
    font-family: var(--font-primary);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all var(--transition-base);
}

.code-tab:hover {
    color: var(--text-primary);
    background: var(--bg-secondary);
}

.code-tab.active {
    color: var(--accent-primary);
    border-bottom-color: var(--accent-primary);
    background: var(--bg-primary);
}

/* Code Content */
.code-content {
    flex: 1;
    position: relative;
    overflow: hidden;
}

.code-tab-content {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    display: none;
    flex-direction: column;
}

.code-tab-content.active {
    display: flex;
}

/* Code Editor - Enhanced with Line Numbers */
.code-editor-container {
    flex: 1;
    display: flex;
    background: var(--bg-primary);
    overflow: hidden;
    position: relative;
}

.code-line-numbers {
    padding: var(--spacing-lg) var(--spacing-sm);
    background: var(--bg-tertiary);
    color: var(--text-tertiary);
    font-family: var(--font-mono);
    font-size: 0.9rem;
    line-height: 1.6;
    text-align: right;
    user-select: none;
    min-width: 50px;
    border-right: 1px solid var(--border-primary);
    overflow: hidden;
}

.code-editor {
    flex: 1;
    padding: var(--spacing-lg);
    background: var(--bg-primary);
    border: none;
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 0.9rem;
    line-height: 1.6;
    resize: none;
    outline: none;
    overflow-y: auto;
    tab-size: 4;
}

.code-editor::-webkit-scrollbar {
    width: 10px;
    height: 10px;
}

.code-editor::-webkit-scrollbar-thumb {
    background: var(--accent-primary);
    border-radius: 5px;
}

/* Run button animation */
.btn-icon.running {
    animation: pulse 1s infinite;
    background: var(--accent-primary) !important;
    color: white !important;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.7; }
}

/* Language Select */
.language-select {
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--bg-tertiary);
    border: 1px solid var(--border-primary);
    border-radius: var(--border-radius-md);
    color: var(--text-primary);
    font-family: var(--font-primary);
    font-size: 0.85rem;
    cursor: pointer;
    transition: all var(--transition-base);
}

.language-select:hover {
    border-color: var(--accent-primary);
}

.language-select:focus {
    outline: none;
    border-color: var(--accent-primary);
    box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.1);
}

/* Output Container */
.output-container {
    flex: 1;
    display: flex;
    flex-direction: column;
    background: var(--bg-primary);
}

.output-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-md) var(--spacing-lg);
    background: var(--bg-tertiary);
    border-bottom: 1px solid var(--border-primary);
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.btn-sm {
    width: 32px;
    height: 32px;
    font-size: 0.85rem;
}

.output-content {
    flex: 1;
    padding: var(--spacing-lg);
    overflow-y: auto;
    font-family: var(--font-mono);
    font-size: 0.85rem;
    line-height: 1.6;
    color: var(--text-secondary);
    white-space: pre-wrap;
}

/* Examples Container */
.examples-container {
    flex: 1;
    padding: var(--spacing-lg);
    overflow-y: auto;
}

.example-card {
    margin-bottom: var(--spacing-lg);
    padding: var(--spacing-lg);
    background: var(--bg-primary);
    border: 1px solid var(--border-primary);
    border-radius: var(--border-radius-md);
    transition: all var(--transition-base);
}

.example-card:hover {
    border-color: var(--accent-primary);
    box-shadow: var(--shadow-md);
}

.example-card h4 {
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.example-card p {
    margin-bottom: var(--spacing-md);
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.example-code {
    padding: var(--spacing-md);
    background: var(--bg-tertiary);
    border-radius: var(--border-radius-sm);
    font-family: var(--font-mono);
    font-size: 0.85rem;
    overflow-x: auto;
}

.btn-load-example {
    margin-top: var(--spacing-md);
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--accent-primary);
    border: none;
    border-radius: var(--border-radius-sm);
    color: white;
    font-size: 0.85rem;
    cursor: pointer;
    transition: all var(--transition-base);
}

.btn-load-example:hover {
    background: var(--accent-hover);
}

/* Code Hints */
.code-hints {
    padding: var(--spacing-lg);
    background: var(--bg-tertiary);
    border-top: 1px solid var(--border-primary);
}

.hint-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--accent-primary);
}

.hint-content {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* ============================================
   Floating Action Buttons
   ============================================ */
.fab-container {
    position: fixed;
    bottom: var(--spacing-xl);
    right: var(--spacing-xl);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
    z-index: 900;
}

.fab {
    width: 56px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--gradient-primary);
    border: none;
    border-radius: 50%;
    color: white;
    font-size: 1.25rem;
    cursor: pointer;
    box-shadow: var(--shadow-lg);
    transition: all var(--transition-base);
}

.fab:hover {
    transform: scale(1.1) translateY(-2px);
    box-shadow: var(--shadow-xl);
}

/* ============================================
   Modal
   ============================================ */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    display: none;
    align-items: center;
    justify-content: center;
    background: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(4px);
    z-index: 2000;
    animation: fadeIn var(--transition-base);
}

.modal.active {
    display: flex;
}

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

.modal-content {
    width: 90%;
    max-width: 800px;
    max-height: 90vh;
    background: var(--bg-secondary);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-xl);
    overflow: hidden;
    animation: slideUp var(--transition-slow);
}

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

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-xl);
    background: var(--gradient-primary);
    color: white;
}

.modal-header h2 {
    margin: 0;
    font-size: 1.5rem;
}

.modal-close {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(255, 255, 255, 0.2);
    border: none;
    border-radius: var(--border-radius-md);
    color: white;
    font-size: 1.25rem;
    cursor: pointer;
    transition: all var(--transition-base);
}

.modal-close:hover {
    background: rgba(255, 255, 255, 0.3);
}

.modal-body {
    padding: var(--spacing-2xl);
    overflow-y: auto;
    max-height: calc(90vh - 120px);
}

/* Welcome Grid */
.welcome-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-2xl);
}

.welcome-card {
    padding: var(--spacing-xl);
    background: var(--bg-primary);
    border: 1px solid var(--border-primary);
    border-radius: var(--border-radius-md);
    text-align: center;
    transition: all var(--transition-base);
}

.welcome-card:hover {
    border-color: var(--accent-primary);
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

.welcome-card i {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-md);
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.welcome-card h3 {
    margin-bottom: var(--spacing-sm);
    font-size: 1.1rem;
    color: var(--text-primary);
}

.welcome-card p {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.welcome-actions {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
}

/* ============================================
   Loading Overlay
   ============================================ */
.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    display: none;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    gap: var(--spacing-lg);
    background: rgba(0, 0, 0, 0.8);
    backdrop-filter: blur(4px);
    z-index: 3000;
}

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

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

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

.loading-overlay p {
    font-size: 1.1rem;
    color: var(--text-secondary);
}

/* ============================================
   Toast Notifications
   ============================================ */
.toast-container {
    position: fixed;
    top: calc(var(--header-height) + var(--spacing-lg));
    right: var(--spacing-lg);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
    z-index: 1500;
}

.toast {
    min-width: 300px;
    padding: var(--spacing-lg);
    background: var(--bg-elevated);
    border: 1px solid var(--border-primary);
    border-radius: var(--border-radius-md);
    box-shadow: var(--shadow-lg);
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    animation: slideInRight var(--transition-base);
}

@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(100px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.toast.success { border-left: 4px solid var(--success); }
.toast.warning { border-left: 4px solid var(--warning); }
.toast.error { border-left: 4px solid var(--error); }
.toast.info { border-left: 4px solid var(--info); }

.toast-icon {
    font-size: 1.25rem;
}

.toast.success .toast-icon { color: var(--success); }
.toast.warning .toast-icon { color: var(--warning); }
.toast.error .toast-icon { color: var(--error); }
.toast.info .toast-icon { color: var(--info); }

.toast-content {
    flex: 1;
}

.toast-title {
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    color: var(--text-primary);
}

.toast-message {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

/* ============================================
   Scrollbar Styles
   ============================================ */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

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

::-webkit-scrollbar-thumb {
    background: var(--border-primary);
    border-radius: 999px;
}

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

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 1200px) {
    :root {
        --sidebar-width: 280px;
    }

    .panel-content {
        padding: var(--spacing-xl);
    }
}

/* Enhanced Mobile Responsive Design */
@media (max-width: 1024px) {
    .header-content {
        padding: 0 var(--spacing-md);
    }

    .panel-footer {
        flex-wrap: wrap;
        justify-content: center;
    }

    .footer-left,
    .footer-right {
        flex-basis: 100%;
        justify-content: center;
        margin-bottom: var(--spacing-sm);
    }
}

@media (max-width: 768px) {
    :root {
        --header-height: 56px;
        --sidebar-width: 280px;
    }

    .main-nav {
        display: none;
    }

    .logo {
        font-size: 1rem;
    }

    .logo i {
        font-size: 1.25rem;
    }

    .sidebar {
        position: fixed;
        top: var(--header-height);
        left: 0;
        bottom: 0;
        z-index: 100;
        box-shadow: var(--shadow-xl);
        transform: translateX(-100%);
        transition: transform var(--transition-base);
    }

    .sidebar:not(.collapsed) {
        transform: translateX(0);
    }

    .content-wrapper {
        flex-direction: column;
    }

    .resizer {
        display: none;
    }

    .panel-left,
    .panel-right {
        min-width: 100%;
        flex: 1 1 auto !important;
    }

    .panel-content {
        padding: var(--spacing-md);
    }

    .panel-content h1 {
        font-size: 1.5rem;
    }

    .panel-content h2 {
        font-size: 1.25rem;
    }

    .panel-footer {
        padding: var(--spacing-md);
    }

    .btn {
        padding: var(--spacing-sm) var(--spacing-md);
        font-size: 0.85rem;
    }

    .fab-container {
        bottom: var(--spacing-md);
        right: var(--spacing-md);
    }

    .fab {
        width: 48px;
        height: 48px;
        font-size: 1.1rem;
    }

    .chapter-info-content {
        grid-template-columns: 1fr;
    }

    .welcome-grid {
        grid-template-columns: 1fr;
    }

    /* Make code editor more mobile-friendly */
    .code-editor {
        font-size: 0.8rem;
    }

    .code-line-numbers {
        font-size: 0.8rem;
        min-width: 40px;
    }

    /* Adjust code tabs for mobile */
    .code-tab {
        padding: var(--spacing-sm) var(--spacing-md);
        font-size: 0.85rem;
    }

    /* Mobile-optimized examples */
    .example-card {
        padding: var(--spacing-md);
    }

    .example-code {
        font-size: 0.75rem;
    }
}

@media (max-width: 480px) {
    .logo span {
        display: none;
    }

    .volume-stats {
        font-size: 0.7rem;
    }

    .module-item {
        padding: var(--spacing-sm) var(--spacing-md);
    }

    .chapter-number {
        min-width: 25px;
        font-size: 0.7rem;
    }

    .module-title {
        font-size: 0.85rem;
    }

    .progress-overview {
        padding: var(--spacing-sm) var(--spacing-md);
    }

    .continue-learning {
        padding: var(--spacing-sm) var(--spacing-md);
    }

    .btn-icon {
        width: 36px;
        height: 36px;
        font-size: 1rem;
    }
}

/* ============================================
   Print Styles
   ============================================ */
@media print {
    .header,
    .sidebar,
    .panel-footer,
    .panel-right,
    .fab-container,
    .resizer {
        display: none !important;
    }

    .panel-left {
        width: 100% !important;
        max-width: 100% !important;
    }

    .panel-content {
        padding: 0;
    }
}

/* ============================================
   Networking & Security Specific Styles
   ============================================ */
/* Icon Colors by Category */
.icon-networking { color: var(--accent-networking); }
.icon-security { color: var(--accent-security); }
.icon-ai { color: #f59e0b; }
.icon-automation { color: #8b5cf6; }
.icon-monitoring { color: #ec4899; }
.icon-troubleshooting { color: #ef4444; }

/* Category Badges */
.category-badge {
    padding: 4px 10px;
    border-radius: var(--border-radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.badge-networking {
    background: rgba(0, 212, 170, 0.2);
    color: var(--accent-networking);
    border: 1px solid var(--accent-networking);
}

.badge-security {
    background: rgba(99, 102, 241, 0.2);
    color: var(--accent-security);
    border: 1px solid var(--accent-security);
}

.badge-ai {
    background: rgba(245, 158, 11, 0.2);
    color: #f59e0b;
    border: 1px solid #f59e0b;
}

.badge-automation {
    background: rgba(139, 92, 246, 0.2);
    color: #8b5cf6;
    border: 1px solid #8b5cf6;
}

/* Chapter Info Card */
.chapter-info {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
    padding: var(--spacing-lg);
    background: var(--bg-tertiary);
    border-radius: var(--border-radius-md);
    border-left: 4px solid var(--accent-primary);
    margin-bottom: var(--spacing-lg);
}

.chapter-info-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.chapter-info-title {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.chapter-info-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-md);
}

.info-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.info-item i {
    color: var(--accent-primary);
    font-size: 1rem;
}

/* Enhanced Code Block */
.code-block-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--bg-tertiary);
    border-bottom: 1px solid var(--border-primary);
    border-radius: var(--border-radius-md) var(--border-radius-md) 0 0;
}

.code-language {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--accent-primary);
    text-transform: uppercase;
}

.code-actions {
    display: flex;
    gap: var(--spacing-xs);
}

/* ============================================
   Utility Classes
   ============================================ */
.hidden { display: none !important; }
.visible { display: block !important; }
.text-center { text-align: center; }
.text-right { text-align: right; }
.mb-sm { margin-bottom: var(--spacing-sm); }
.mb-md { margin-bottom: var(--spacing-md); }
.mb-lg { margin-bottom: var(--spacing-lg); }
.mt-sm { margin-top: var(--spacing-sm); }
.mt-md { margin-top: var(--spacing-md); }
.mt-lg { margin-top: var(--spacing-lg); }

/* ============================================
   Notebook Styles
   ============================================ */
.notebook-container {
    height: 100%;
    overflow-y: auto;
    padding: var(--spacing-lg);
    background: var(--bg-primary);
}

.notebook-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-md);
    background: var(--bg-secondary);
    border-radius: var(--border-radius-md);
    margin-bottom: var(--spacing-lg);
    border: 1px solid var(--border-color);
}

.notebook-title {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-weight: 600;
    font-size: 1.1rem;
    color: var(--text-primary);
}

.notebook-title i {
    color: var(--accent-primary);
}

.notebook-actions {
    display: flex;
    gap: 6px;
    align-items: center;
}

/* Compact buttons for notebook header */
.notebook-actions .btn {
    padding: 6px 12px;
    font-size: 0.75rem;
    gap: 4px;
    border-radius: 6px;
    font-weight: 500;
}

.notebook-actions .btn i {
    font-size: 0.85rem;
}

/* Icon-only button for refresh */
.notebook-actions .btn-icon-only {
    padding: 6px;
    width: 28px;
    height: 28px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.notebook-cells {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

.notebook-cell {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-md);
    overflow: hidden;
    transition: all var(--transition-base);
}

.notebook-cell:hover {
    border-color: var(--accent-primary);
    box-shadow: var(--shadow-md);
}

.notebook-cell-markdown {
    border-left: 3px solid var(--info);
}

.notebook-cell-code {
    border-left: 3px solid var(--accent-primary);
}

.cell-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--bg-tertiary);
    border-bottom: 1px solid var(--border-color);
}

.cell-label {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--text-secondary);
    font-weight: 600;
}

.cell-actions {
    display: flex;
    gap: var(--spacing-xs);
}

.cell-content {
    padding: var(--spacing-md);
}

.code-content pre {
    margin: 0;
    background: transparent;
    border: none;
    padding: 0;
}

.code-content code {
    background: transparent;
    padding: 0;
    font-size: 0.9rem;
    line-height: 1.6;
}

.markdown-content {
    color: var(--text-primary);
    line-height: 1.7;
}

.markdown-content h1,
.markdown-content h2,
.markdown-content h3,
.markdown-content h4 {
    color: var(--text-primary);
    margin-top: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
}

.markdown-content h1 { font-size: 1.8rem; }
.markdown-content h2 { font-size: 1.5rem; }
.markdown-content h3 { font-size: 1.2rem; }
.markdown-content h4 { font-size: 1rem; }

.markdown-content p {
    margin-bottom: var(--spacing-sm);
}

.markdown-content code {
    background: var(--bg-tertiary);
    padding: 2px 6px;
    border-radius: 3px;
    font-family: var(--font-mono);
    font-size: 0.9em;
}

.markdown-content pre {
    background: var(--bg-tertiary);
    padding: var(--spacing-md);
    border-radius: var(--border-radius-sm);
    overflow-x: auto;
    margin: var(--spacing-sm) 0;
}

.markdown-content pre code {
    background: transparent;
    padding: 0;
}

.markdown-content ul, .markdown-content ol {
    margin-left: var(--spacing-lg);
    margin-bottom: var(--spacing-sm);
}

.markdown-content li {
    margin-bottom: var(--spacing-xs);
}

.cell-output {
    margin-top: var(--spacing-md);
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--border-color);
}

.output-label {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--text-secondary);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.output-content {
    padding: var(--spacing-md);
    background: var(--bg-tertiary);
    border-radius: var(--border-radius-sm);
}

.output-stream,
.output-result {
    margin: 0;
    padding: var(--spacing-sm);
    background: transparent;
    color: var(--text-primary);
    font-family: var(--font-mono);
    font-size: 0.85rem;
    line-height: 1.5;
    white-space: pre-wrap;
    word-wrap: break-word;
}

.output-error {
    margin: 0;
    padding: var(--spacing-sm);
    background: rgba(239, 68, 68, 0.1);
    color: var(--error);
    font-family: var(--font-mono);
    font-size: 0.85rem;
    line-height: 1.5;
    white-space: pre-wrap;
    word-wrap: break-word;
    border-left: 3px solid var(--error);
}

.output-html {
    color: var(--text-primary);
}

.output-image {
    max-width: 100%;
    height: auto;
    margin-top: var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    border: 1px solid var(--border-color);
}

.notebook-loading,
.notebook-error,
.notebook-placeholder {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-2xl);
    text-align: center;
    min-height: 400px;
}

.notebook-loading .loading-spinner {
    width: 50px;
    height: 50px;
    border: 4px solid var(--border-color);
    border-top-color: var(--accent-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: var(--spacing-lg);
}

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

.notebook-loading p,
.notebook-error p,
.notebook-placeholder p {
    color: var(--text-secondary);
    margin: var(--spacing-sm) 0;
}

.notebook-error i,
.notebook-placeholder i {
    font-size: 3rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    opacity: 0.5;
}

.notebook-error h3,
.notebook-placeholder h3 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
}

.notebook-error .btn {
    margin-top: var(--spacing-md);
}

/* Responsive notebook styles */
@media (max-width: 768px) {
    .notebook-header {
        flex-direction: column;
        gap: var(--spacing-sm);
    }

    .notebook-actions {
        gap: 4px;
    }

    .notebook-actions .btn {
        padding: 5px 10px;
        font-size: 0.7rem;
    }

    .notebook-actions .btn-icon-only {
        padding: 5px;
        width: 26px;
        height: 26px;
    }
}

.notebook-cell-count {
    font-size: 0.85rem;
    color: var(--text-secondary);
    padding: 2px 8px;
    background: var(--bg-tertiary);
    border-radius: var(--border-radius-sm);
    margin-left: var(--spacing-sm);
}

/* Theory content tables — high visibility */
.panel-content table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--spacing-lg) 0;
    font-size: 0.9rem;
}

.panel-content th {
    background: rgba(99,102,241,0.12);
    color: #a5b4fc;
    padding: 10px 14px;
    text-align: left;
    font-weight: 600;
    border-bottom: 1px solid rgba(99,102,241,0.25);
    font-size: 0.85rem;
    letter-spacing: 0.02em;
}

.panel-content td {
    padding: 9px 14px;
    color: #c9d1d9;
    border-bottom: 1px solid rgba(255,255,255,0.06);
    line-height: 1.6;
}

.panel-content tr:hover td {
    background: rgba(99,102,241,0.04);
}

/* Horizontal rule */
.panel-content hr {
    border: none;
    border-top: 1px solid rgba(99,102,241,0.2);
    margin: var(--spacing-2xl) 0;
}

/* Strong and em inside prose */
.panel-content strong {
    color: #e6edf3;
    font-weight: 600;
}

.panel-content em {
    color: #c9d1d9;
}

/* ============================================
   Tabbed Learning Layout (v1)
   ============================================ */

/* Full-width content area — remove split screen */
.content-wrapper {
    flex-direction: column !important;
}

/* Hide old split-screen elements */
.resizer  { display: none !important; }
.panel-left  { display: none !important; }
.panel-right { display: none !important; }

/* ── Learning Panel ─────────────────────────────── */
.learning-panel {
    flex: 1;
    display: flex;
    flex-direction: column;
    overflow: hidden;
    background: var(--bg-primary);
}

/* ── Module Banner ──────────────────────────────── */
.module-banner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 28px;
    background: #0f1629;
    border-bottom: 1px solid rgba(99,102,241,0.2);
    flex-shrink: 0;
    gap: 16px;
}

.banner-left {
    display: flex;
    flex-direction: column;
    gap: 5px;
    min-width: 0;
}

.volume-badge {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: #818cf8;
    background: rgba(99,102,241,0.1);
    border: 1px solid rgba(99,102,241,0.22);
    border-radius: 20px;
    padding: 3px 10px;
    width: fit-content;
}

.banner-title {
    font-size: 1.2rem;
    font-weight: 700;
    color: #f1f5f9;
    letter-spacing: -0.02em;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    max-width: 680px;
    margin: 0;
    line-height: 1.3;
}

.banner-right {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-shrink: 0;
}

.banner-actions {
    display: flex;
    gap: 4px;
}

/* ── Tab Navigation ─────────────────────────────── */
.learning-tabs {
    display: flex;
    align-items: center;
    gap: 4px;
    padding: 10px 20px;
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-primary);
    flex-shrink: 0;
}

.ltab {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 7px 15px;
    background: rgba(255,255,255,0.06);
    border: 1px solid rgba(255,255,255,0.15);
    border-radius: 8px;
    color: #cbd5e1;
    font-family: var(--font-primary);
    font-size: 0.8125rem;
    font-weight: 500;
    cursor: pointer;
    transition: background 160ms ease, color 160ms ease, border-color 160ms ease, box-shadow 160ms ease;
    white-space: nowrap;
    position: relative;
    line-height: 1;
}

.ltab:hover {
    color: #f1f5f9;
    background: rgba(255,255,255,0.12);
    border-color: rgba(255,255,255,0.25);
}

.ltab.active {
    font-weight: 600;
}

/* Icon: constrained size prevents oversized brand logos (e.g. fa-python) */
.ltab i {
    font-size: 0.78rem;
    width: 14px;
    text-align: center;
    flex-shrink: 0;
    line-height: 1;
    overflow: hidden;
}

/* Per-tab semantic accent colours */
.ltab[data-tab="concept"]:hover { color: #818cf8; }
.ltab[data-tab="concept"].active {
    color: #a5b4fc;
    background: rgba(99,102,241,0.14);
    border-color: rgba(99,102,241,0.30);
    box-shadow: 0 0 12px rgba(99,102,241,0.08);
}

.ltab[data-tab="code"]:hover { color: #00d4aa; }
.ltab[data-tab="code"].active {
    color: #5eead4;
    background: rgba(0,212,170,0.12);
    border-color: rgba(0,212,170,0.28);
    box-shadow: 0 0 12px rgba(0,212,170,0.07);
}

.ltab[data-tab="lab"]:hover { color: #f59e0b; }
.ltab[data-tab="lab"].active {
    color: #fcd34d;
    background: rgba(245,158,11,0.12);
    border-color: rgba(245,158,11,0.28);
    box-shadow: 0 0 12px rgba(245,158,11,0.07);
}

.ltab[data-tab="quiz"]:hover { color: #a855f7; }
.ltab[data-tab="quiz"].active {
    color: #d8b4fe;
    background: rgba(168,85,247,0.12);
    border-color: rgba(168,85,247,0.28);
    box-shadow: 0 0 12px rgba(168,85,247,0.07);
}

/* ── Tab Panels ─────────────────────────────────── */
.tab-panels {
    flex: 1;
    overflow: hidden;
    position: relative;
}

.tab-panel {
    position: absolute;
    inset: 0;
    display: none;
    flex-direction: column;
    overflow: hidden;
}

.tab-panel.active { display: flex; }

/* Concept tab — centered prose */
#tab-concept {
    overflow-y: auto;
    padding: 32px 40px;
    align-items: flex-start;
}

#tab-concept .panel-content {
    flex: none;
    padding: 0;
    max-width: 820px;
    width: 100%;
    margin: 0 auto;
    overflow-y: visible;
}

/* Code tab */
#tab-code {
    overflow-y: auto;
    padding: 28px 32px;
}

.code-cards-container {
    display: flex;
    flex-direction: column;
    gap: 24px;
    max-width: 900px;
    margin: 0 auto;
    width: 100%;
}

.code-card {
    background: #0d1117;
    border: 1px solid rgba(99,102,241,0.18);
    border-left: 3px solid #6366f1;
    border-radius: 10px;
    overflow: hidden;
}

.code-card-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 9px 16px;
    background: rgba(99,102,241,0.07);
    border-bottom: 1px solid rgba(99,102,241,0.13);
}

.code-card-label {
    font-size: 0.72rem;
    font-weight: 600;
    color: #818cf8;
    text-transform: uppercase;
    letter-spacing: 0.07em;
}

.code-card-lang {
    font-size: 0.68rem;
    color: var(--text-tertiary);
    background: rgba(99,102,241,0.1);
    padding: 2px 8px;
    border-radius: 4px;
    font-family: var(--font-mono);
}

.code-card pre {
    margin: 0;
    padding: 16px;
    background: transparent;
    border: none;
    font-size: 0.875rem;
    line-height: 1.7;
    overflow-x: auto;
}

.code-card pre code {
    background: transparent;
    color: var(--text-primary);
    padding: 0;
    border: none;
    font-size: inherit;
}

.code-empty {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 300px;
    color: var(--text-tertiary);
    text-align: center;
    gap: 14px;
}

.code-empty i {
    font-size: 3rem;
    opacity: 0.35;
}

.code-empty p { font-size: 0.95rem; }

/* Lab tab — notebook fills height */
#tab-lab { overflow: hidden; }
#tab-lab .notebook-container { height: 100%; overflow-y: auto; }

/* Quiz placeholder */
#tab-quiz {
    align-items: center;
    justify-content: center;
}

.quiz-placeholder {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 60px 32px;
    text-align: center;
    gap: 16px;
}

.quiz-placeholder i {
    font-size: 3.5rem;
    color: #6366f1;
    opacity: 0.4;
}

.quiz-placeholder h3 {
    font-size: 1.25rem;
    color: var(--text-secondary);
    font-weight: 600;
}

.quiz-placeholder p {
    color: var(--text-tertiary);
    max-width: 400px;
    line-height: 1.65;
    font-size: 0.95rem;
}

/* ── Learning Footer ─────────────────────────────── */
.learning-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 13px 28px;
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-primary);
    flex-shrink: 0;
    gap: 12px;
}

/* Responsive */
@media (max-width: 640px) {
    .module-banner { padding: 10px 14px; }
    .banner-title  { font-size: 0.95rem; max-width: 220px; }
    .ltab span     { display: none; }
    .ltab          { padding: 10px 12px; }
    #tab-concept   { padding: 18px 14px; }
    .learning-footer { padding: 10px 14px; }
}

/* ============================================
   Visual Upgrade v1 — Dynamic Learning UI
   ============================================ */

/* ── Tab Transitions (override display:none) ── */
.tab-panels .tab-panel {
    display: flex !important;
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transform: translateY(10px);
    transition: opacity 230ms ease, transform 230ms ease, visibility 0ms 230ms;
}
.tab-panels .tab-panel.active {
    opacity: 1;
    visibility: visible;
    pointer-events: all;
    transform: translateY(0);
    transition: opacity 230ms ease, transform 230ms ease, visibility 0ms 0ms;
}

/* ── Banner Canvas Background ─────────────────── */
.module-banner { position: relative; overflow: hidden; }
#banner-canvas {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    opacity: 0.3;
    pointer-events: none;
}
.banner-left, .banner-right { position: relative; z-index: 1; }

/* ── Banner Title Transition ─────────────────── */
.banner-title {
    transition: opacity 150ms ease, transform 150ms ease;
}
.banner-title.fading {
    opacity: 0;
    transform: translateY(6px);
}

/* ── Callout Boxes ───────────────────────────── */
.callout {
    display: flex;
    gap: 14px;
    padding: 14px 18px;
    border-radius: 10px;
    margin: 18px 0;
    border: 1px solid;
    line-height: 1.65;
    font-size: 0.93rem;
    animation: calloutIn 350ms ease both;
}
@keyframes calloutIn {
    from { opacity: 0; transform: translateX(-8px); }
    to   { opacity: 1; transform: translateX(0); }
}
.callout-icon { font-size: 1.1rem; flex-shrink: 0; margin-top: 2px; }
.callout-body { flex: 1; }
.callout-body > strong {
    display: block;
    font-size: 0.78rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.07em;
    margin-bottom: 5px;
}
.callout-body p { margin: 0; color: inherit; font-style: normal; }

.callout-tip     { background: rgba(0,212,170,0.07);  border-color: rgba(0,212,170,0.3);  color: #99f6e4; }
.callout-tip     .callout-icon { color: #00d4aa; }
.callout-tip     .callout-body > strong { color: #00d4aa; }

.callout-note    { background: rgba(99,102,241,0.07); border-color: rgba(99,102,241,0.3); color: #c4b5fd; }
.callout-note    .callout-icon { color: #818cf8; }
.callout-note    .callout-body > strong { color: #818cf8; }

.callout-warning { background: rgba(245,158,11,0.07); border-color: rgba(245,158,11,0.3); color: #fcd34d; }
.callout-warning .callout-icon { color: #f59e0b; }
.callout-warning .callout-body > strong { color: #f59e0b; }

.callout-rule    { background: rgba(236,72,153,0.07); border-color: rgba(236,72,153,0.3); color: #f9a8d4; }
.callout-rule    .callout-icon { color: #ec4899; }
.callout-rule    .callout-body > strong { color: #ec4899; }

/* ── Copy Button on Code Blocks ──────────────── */
.code-wrapper { position: relative; }
.copy-code-btn {
    position: absolute;
    top: 8px;
    right: 8px;
    display: flex;
    align-items: center;
    gap: 5px;
    padding: 4px 10px;
    background: rgba(99,102,241,0.12);
    border: 1px solid rgba(99,102,241,0.22);
    border-radius: 6px;
    color: #818cf8;
    font-size: 0.72rem;
    font-family: var(--font-primary);
    font-weight: 500;
    cursor: pointer;
    opacity: 0;
    transition: all 160ms ease;
    z-index: 3;
}
.code-wrapper:hover .copy-code-btn { opacity: 1; }
.copy-code-btn:hover {
    background: rgba(99,102,241,0.22);
    color: #c4b5fd;
}
.copy-code-btn.copied {
    opacity: 1 !important;
    color: #00d4aa;
    border-color: rgba(0,212,170,0.3);
    background: rgba(0,212,170,0.08);
}
.copy-code-btn i { font-size: 0.7rem; }
#tab-concept .panel-content pre,
.code-card { position: relative; overflow: visible; }
.code-card .code-wrapper { border-radius: 0; }
.code-card .copy-code-btn { top: 6px; right: 6px; }
.code-card pre { border-radius: 0 !important; }

/* ── Content Reveal ──────────────────────────── */
.reveal-item {
    opacity: 0;
    transform: translateY(14px);
    transition: opacity 420ms ease, transform 420ms ease;
}
.reveal-item.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ── H2 Accent Left Bar ─────────────────────── */
#tab-concept .panel-content h2 {
    position: relative;
    padding-left: 16px;
    margin-left: 0;
}
#tab-concept .panel-content h2::before {
    content: '';
    position: absolute;
    left: 0; top: 2px; bottom: 2px;
    width: 3px;
    background: linear-gradient(to bottom, #6366f1, #00d4aa);
    border-radius: 3px;
}

/* ── Chapter info gradient border ───────────── */
.chapter-info {
    background: linear-gradient(135deg, rgba(99,102,241,0.07) 0%, rgba(0,212,170,0.04) 100%);
    border-left-color: transparent;
    border-image: linear-gradient(to bottom, #6366f1, #00d4aa) 1;
}

/* ── Open in Colab banner ────────────────────── */
.open-colab-banner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 9px 20px;
    background: linear-gradient(90deg, rgba(245,158,11,0.08) 0%, rgba(99,102,241,0.08) 100%);
    border-bottom: 1px solid rgba(245,158,11,0.18);
    flex-shrink: 0;
    gap: 12px;
}
.open-colab-banner span {
    font-size: 0.83rem;
    color: var(--text-secondary);
}
.btn-open-colab {
    display: flex;
    align-items: center;
    gap: 7px;
    padding: 6px 14px;
    background: linear-gradient(135deg, #f59e0b 0%, #d97706 100%);
    border: none;
    border-radius: 7px;
    color: #1a1a1a;
    font-size: 0.78rem;
    font-weight: 700;
    cursor: pointer;
    transition: all 160ms ease;
    font-family: var(--font-primary);
    text-decoration: none;
    white-space: nowrap;
}
.btn-open-colab:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 14px rgba(245,158,11,0.4);
    color: #1a1a1a;
}

/* ── Tab badge counter ───────────────────────── */
.ltab-badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 18px;
    height: 18px;
    padding: 0 5px;
    background: rgba(99,102,241,0.18);
    border-radius: 10px;
    font-size: 0.68rem;
    font-weight: 700;
    color: #818cf8;
    margin-left: 2px;
    line-height: 1;
}
.ltab.active .ltab-badge {
    background: rgba(99,102,241,0.28);
}

/* ── Celebration canvas ──────────────────────── */
#celebration-canvas {
    position: fixed;
    inset: 0;
    pointer-events: none;
    z-index: 9999;
}

/* ── Hover lift on module items ──────────────── */
.module-item:hover {
    transform: translateX(3px);
}
.module-item { transition: all 180ms ease !important; }

/* ── Code card hover ─────────────────────────── */
.code-card {
    transition: border-color 200ms ease, box-shadow 200ms ease;
}
.code-card:hover {
    border-color: rgba(99,102,241,0.4);
    box-shadow: 0 0 0 1px rgba(99,102,241,0.15), 0 4px 16px rgba(0,0,0,0.25);
}

/* ── Lab placeholder icon animation ─────────── */
.notebook-placeholder i,
.notebook-error i {
    animation: float 3s ease-in-out infinite;
}
@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-8px); }
}

/* ── Module complete glow on sidebar ────────── */
.module-item.completed {
    position: relative;
}
.module-item.completed::after {
    content: '';
    position: absolute;
    left: 0; top: 0; bottom: 0;
    width: 3px;
    background: linear-gradient(to bottom, #3fb950, #00d4aa);
    border-radius: 0 2px 2px 0;
}

/* ============================================
   Code Explanation Cards (Junior-friendly)
   ============================================ */

.code-explain-card {
    margin-top: 0;
    padding: 18px 22px 16px;
    background: rgba(15, 23, 42, 0.6);
    border: 1px solid rgba(99,102,241,0.15);
    border-top: none;
    border-radius: 0 0 10px 10px;
    animation: explainIn 300ms ease both;
}

@keyframes explainIn {
    from { opacity: 0; transform: translateY(-4px); }
    to   { opacity: 1; transform: translateY(0); }
}

.explain-label {
    display: flex;
    align-items: center;
    gap: 7px;
    font-size: 0.7rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.09em;
    color: #6366f1;
    margin-bottom: 10px;
    opacity: 0.9;
}
.explain-label i { font-size: 0.72rem; }

.explain-overview {
    font-size: 0.9rem;
    color: #c9d1d9;
    line-height: 1.65;
    margin-bottom: 14px;
    padding-bottom: 12px;
    border-bottom: 1px solid rgba(99,102,241,0.12);
}
.explain-overview strong { color: #e2e8f0; }

.explain-bullets {
    display: flex;
    flex-direction: column;
    gap: 9px;
}

.explain-bullet {
    display: flex;
    gap: 10px;
    align-items: flex-start;
    font-size: 0.855rem;
    color: #b6c2cc;
    line-height: 1.6;
}

.explain-icon {
    flex-shrink: 0;
    width: 22px;
    text-align: center;
    font-size: 0.9rem;
    margin-top: 1px;
}

.explain-text code {
    background: rgba(99,102,241,0.13);
    border: 1px solid rgba(99,102,241,0.2);
    border-radius: 4px;
    padding: 1px 6px;
    font-family: var(--font-mono);
    font-size: 0.82em;
    color: #a5b4fc;
}
.explain-text strong { color: #dde3ea; font-weight: 600; }
.explain-text em     { color: #94a3b8; font-style: italic; }

/* Group code + explanation into a card unit */
.code-block-unit {
    display: flex;
    flex-direction: column;
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 2px 12px rgba(0,0,0,0.3);
    margin-bottom: 28px;
    transition: box-shadow 200ms ease;
}
.code-block-unit:hover {
    box-shadow: 0 4px 20px rgba(99,102,241,0.18), 0 2px 12px rgba(0,0,0,0.4);
}
.code-block-unit .code-card {
    margin-bottom: 0;
    border-radius: 0 !important;
    border-bottom: none;
}
.code-block-unit > .code-card:first-child {
    border-radius: 10px 10px 0 0 !important;
}
.code-block-unit .code-explain-card {
    border-radius: 0 0 10px 10px;
}
.code-cards-container { gap: 0 !important; }


/* ── Bright comment color in all code blocks ───────────────────────────────
   highlight.js atom-one-dark uses #5c6370 for .hljs-comment — nearly invisible.
   Override to a warm amber-orange so the explanatory # comments in every
   chapter stand out clearly against the dark code background.
   Applies to all pre/code blocks site-wide (Concept, Code, Lab tabs).
*/
.hljs-comment,
.hljs-quote {
  color: #f5a623 !important;   /* warm amber-orange — readable on dark bg */
  font-style: italic;
  font-weight: 500;
}

/* ── Curriculum Section ─────────────────────────────────────────────── */
.curriculum-section {
    padding: 2.5rem 2rem;
    max-width: 1100px;
    margin: 0 auto;
    width: 100%;
    box-sizing: border-box;
}
.curriculum-header {
    text-align: center;
    margin-bottom: 2.5rem;
}
.curriculum-header h1 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}
.curriculum-subtitle {
    color: var(--text-secondary);
    font-size: 1rem;
    margin-bottom: 1rem;
}
.curriculum-meta {
    display: flex;
    justify-content: center;
    gap: 1.5rem;
    flex-wrap: wrap;
    color: var(--accent-blue);
    font-size: 0.875rem;
}
.curriculum-meta span {
    display: flex;
    align-items: center;
    gap: 0.4rem;
}
.curriculum-grid {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}
.curriculum-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.25rem 1.5rem;
    display: flex;
    align-items: flex-start;
    gap: 1.25rem;
    transition: border-color 0.2s, box-shadow 0.2s;
}
.curriculum-card:hover {
    border-color: var(--accent-blue);
    box-shadow: 0 4px 20px rgba(100, 181, 246, 0.1);
}
.curriculum-card-number {
    min-width: 2rem;
    height: 2rem;
    background: var(--accent-blue);
    color: #0a0f1e;
    font-weight: 700;
    font-size: 0.875rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    margin-top: 2px;
}
.curriculum-card-icon {
    font-size: 1.4rem;
    color: var(--accent-blue);
    min-width: 1.8rem;
    text-align: center;
    margin-top: 2px;
    flex-shrink: 0;
}
.curriculum-card-body {
    flex: 1;
}
.curriculum-card-body h3 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    margin: 0 0 0.35rem 0;
}
.curriculum-card-body p {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin: 0 0 0.6rem 0;
    line-height: 1.5;
}
.curriculum-card-tags {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}
.ctag {
    font-size: 0.75rem;
    padding: 0.15rem 0.6rem;
    border-radius: 20px;
    background: var(--bg-tertiary, var(--bg-primary));
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 0.3rem;
}
.curriculum-start-btn {
    flex-shrink: 0;
    align-self: center;
    white-space: nowrap;
}
@media (max-width: 600px) {
    .curriculum-card { flex-wrap: wrap; }
    .curriculum-start-btn { width: 100%; justify-content: center; }
}

/* ── Email Capture ───────────────────────────────────────────── */
.modal-signup {
    border-top: 1px solid var(--border-color);
    padding: 1.25rem 2rem 0.5rem;
    text-align: center;
}
.modal-signup-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin: 0 0 0.75rem 0;
}
.modal-signup-form {
    display: flex;
    gap: 0.5rem;
    max-width: 420px;
    margin: 0 auto;
}
.modal-signup-meta {
    font-size: 0.75rem;
    color: var(--text-tertiary);
    margin: 0.5rem 0 0 0;
}
.signup-email-input {
    flex: 1;
    padding: 0.5rem 0.875rem;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    color: var(--text-primary);
    font-size: 0.875rem;
    outline: none;
    transition: border-color 0.15s;
}
.signup-email-input:focus {
    border-color: var(--accent-blue);
}
.signup-submit-btn { white-space: nowrap; }

.email-bar {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    z-index: 1200;
    padding: 0.875rem 1.5rem;
}
.email-bar-content {
    max-width: 900px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    gap: 1.5rem;
    flex-wrap: wrap;
}
.email-bar-text {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 0.2rem;
}
.email-bar-text strong {
    color: var(--text-primary);
    font-size: 0.9rem;
}
.email-bar-text span {
    color: var(--text-secondary);
    font-size: 0.8rem;
}
.email-bar-form {
    display: flex;
    gap: 0.5rem;
}
.email-bar-close {
    background: none;
    border: none;
    color: var(--text-tertiary);
    font-size: 1.4rem;
    cursor: pointer;
    padding: 0 0.25rem;
    line-height: 1;
}
.email-bar-close:hover { color: var(--text-primary); }
@media (max-width: 600px) {
    .email-bar-form { width: 100%; }
    .modal-signup-form { flex-direction: column; }
}