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

:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary-color: #8b5cf6;
    --accent-color: #ec4899;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --info-color: #3b82f6;
    
    --bg-color: #0f172a;
    --bg-secondary: #1e293b;
    --surface-color: #1e293b;
    --surface-light: #334155;
    --surface-lighter: #475569;
    --code-bg-color: #1a1a2e;
    --code-text-color: #a78bfa;
    
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-tertiary: #94a3b8;
    --border-color: #475569;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.5);
    
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 300ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 500ms cubic-bezier(0.4, 0, 0.2, 1);
    
    --border-radius-sm: 6px;
    --border-radius: 12px;
    --border-radius-lg: 16px;
    --border-radius-xl: 24px;
}

/* Light theme - define on :root (html) so all children inherit */
:root[data-theme="light"],
html[data-theme="light"] {
    --bg-color: #f8fafc;
    --bg-secondary: #f1f5f9;
    --surface-color: #ffffff;
    --surface-light: #f1f5f9;
    --surface-lighter: #e2e8f0;
    --code-bg-color: #f1f5f9;
    --code-text-color: #475569;
    
    --text-primary: #0f172a;
    --text-secondary: #334155;
    --text-tertiary: #64748b;
    --border-color: #cbd5e1;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.1);
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.15);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.2);
}

/* Light mode specific overrides */
[data-theme="light"] .header-content {
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    opacity: 1;
}

[data-theme="light"] .progress-container {
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    opacity: 1;
}

[data-theme="light"] .sidebar {
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    opacity: 1;
}

[data-theme="light"] .course-content {
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    opacity: 1;
}

/* Code blocks now use CSS variables that change with theme */

[data-theme="light"] .certificate {
    background: white;
    color: #1a1a2e;
}

[data-theme="light"] .modal-content {
    background: var(--surface-color);
    border: 1px solid var(--border-color);
}

[data-theme="light"] .quiz-container {
    background: var(--surface-light);
}

[data-theme="light"] .exercise-box {
    background: var(--surface-light);
}

[data-theme="light"] .code-playground {
    background: var(--surface-light);
}

[data-theme="light"] .playground-result {
    background: var(--bg-color);
    color: var(--text-secondary);
}

[data-theme="light"] .interactive-input {
    background: var(--bg-color);
    color: var(--text-primary);
}

[data-theme="light"] .playground-textarea {
    background: var(--bg-color);
    color: var(--text-primary);
}

[data-theme="light"] .name-input {
    background: var(--surface-light);
    color: var(--text-primary);
}

[data-theme="light"] .progress-bar {
    background: var(--surface-lighter);
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.1);
}

[data-theme="light"] .quiz-option {
    background: var(--surface-color);
}

[data-theme="light"] .quiz-option:hover {
    background: rgba(99, 102, 241, 0.1);
}

[data-theme="light"] .quiz-option.selected {
    background: rgba(99, 102, 241, 0.15);
}

[data-theme="light"] .module-list a {
    color: var(--text-secondary);
}

[data-theme="light"] .module-list a:hover {
    background: var(--surface-light);
    color: var(--text-primary);
}

[data-theme="light"] .module-list a.active {
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.15), rgba(139, 92, 246, 0.15));
    color: var(--primary-color);
    border: 1px solid rgba(99, 102, 241, 0.3);
}

[data-theme="light"] .achievement-badge {
    background: var(--surface-light);
}

[data-theme="light"] .achievement-card {
    background: var(--surface-light);
}

[data-theme="light"] .btn-secondary {
    background: var(--surface-light);
    color: var(--text-primary);
}

[data-theme="light"] .btn-icon {
    background: var(--surface-light);
}

[data-theme="light"] .btn-collapse {
    color: var(--text-secondary);
}

[data-theme="light"] .btn-collapse:hover {
    background: var(--surface-light);
    color: var(--text-primary);
}

[data-theme="light"] .modal-close {
    background: var(--surface-light);
    color: var(--text-primary);
}

[data-theme="light"] .modal-close:hover {
    background: var(--danger-color);
    color: white;
}

[data-theme="light"] .toast {
    background: var(--surface-color);
    border: 1px solid var(--border-color);
}


[data-theme="light"] .example-box {
    background: rgba(99, 102, 241, 0.08);
}

[data-theme="light"] .tip-box {
    background: rgba(16, 185, 129, 0.08);
}

[data-theme="light"] .warning-box {
    background: rgba(245, 158, 11, 0.08);
}

[data-theme="light"] .info-box {
    background: rgba(59, 130, 246, 0.08);
}

/* Body background updates automatically via CSS variables */

[data-theme="light"] .animated-bg {
    opacity: 0.2;
}

[data-theme="light"] .gradient-orb {
    opacity: 0.03;
    filter: blur(120px);
}

[data-theme="light"] ::-webkit-scrollbar-track {
    background: var(--surface-light);
}

[data-theme="light"] ::-webkit-scrollbar-thumb {
    background: var(--surface-lighter);
}

[data-theme="light"] ::-webkit-scrollbar-thumb:hover {
    background: var(--primary-color);
}

[data-theme="light"] ::selection {
    background: rgba(99, 102, 241, 0.2);
    color: var(--text-primary);
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg-color) !important;
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
    overflow-x: hidden;
    position: relative;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    /* Prevent text size adjustment on iOS */
    -webkit-text-size-adjust: 100%;
    text-size-adjust: 100%;
    transition: background-color 0.3s ease;
}

/* Animated Background */
.animated-bg {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    overflow: hidden;
}

.gradient-orb {
    position: absolute;
    border-radius: 50%;
    filter: blur(80px);
    opacity: 0.3;
    animation: float 20s infinite ease-in-out;
}

.orb-1 {
    width: 500px;
    height: 500px;
    background: radial-gradient(circle, var(--primary-color), transparent);
    top: -250px;
    left: -250px;
    animation-delay: 0s;
}

.orb-2 {
    width: 400px;
    height: 400px;
    background: radial-gradient(circle, var(--secondary-color), transparent);
    bottom: -200px;
    right: -200px;
    animation-delay: 7s;
}

.orb-3 {
    width: 350px;
    height: 350px;
    background: radial-gradient(circle, var(--accent-color), transparent);
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    animation-delay: 14s;
}

@keyframes float {
    0%, 100% { transform: translate(0, 0) scale(1); }
    25% { transform: translate(50px, 50px) scale(1.1); }
    50% { transform: translate(-30px, 80px) scale(0.9); }
    75% { transform: translate(70px, -40px) scale(1.05); }
}

.container {
    max-width: 1600px;
    margin: 0 auto;
    padding: 2rem;
    position: relative;
    z-index: 1;
    width: 100%;
    box-sizing: border-box;
}

/* Header */
.main-header {
    margin-bottom: 2rem;
    animation: slideDown 0.6s ease-out;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--surface-color);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 1.5rem 2rem;
    box-shadow: var(--shadow-lg);
    opacity: 0.95;
}

.logo-section {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.logo-icon {
    font-size: 3rem;
    animation: bounce 4s ease-in-out infinite;
}

@keyframes bounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-10px); }
}

.main-header h1 {
    font-size: 2rem;
    font-weight: 800;
    margin-bottom: 0.25rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color), var(--accent-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1rem;
    font-weight: 400;
}

.header-actions {
    display: flex;
    gap: 1rem;
    align-items: center;
}

/* Progress Container */
.progress-container {
    background: var(--surface-color);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 2rem;
    margin-bottom: 2rem;
    box-shadow: var(--shadow-lg);
    animation: fadeIn 0.6s ease-out 0.2s both;
    opacity: 0.95;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

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

.progress-info {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.progress-label {
    font-size: 0.875rem;
    color: var(--text-tertiary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    font-weight: 600;
}

.progress-text {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

.stats {
    display: flex;
    gap: 2rem;
}

.stat-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.25rem;
}

.stat-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-light);
}

.stat-label {
    font-size: 0.75rem;
    color: var(--text-tertiary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.progress-bar {
    width: 100%;
    height: 16px;
    background: var(--surface-light);
    border-radius: 8px;
    overflow: hidden;
    position: relative;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.3);
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color), var(--accent-color));
    border-radius: 8px;
    transition: width 0.5s cubic-bezier(0.4, 0, 0.2, 1);
    width: 0%;
    position: relative;
    box-shadow: 0 0 20px rgba(99, 102, 241, 0.5);
}

.progress-glow {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.3), transparent);
    animation: shimmer 3s ease-in-out infinite;
}

[data-theme="light"] .progress-glow {
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.6), transparent);
}

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

/* Main Content Layout */
.main-content {
    display: grid;
    grid-template-columns: 320px 1fr;
    gap: 2rem;
    margin-bottom: 2rem;
    animation: fadeIn 0.6s ease-out 0.4s both;
    transition: grid-template-columns var(--transition-base);
}

/* When sidebar is collapsed, adjust grid to only show main content */
.main-content.sidebar-collapsed {
    grid-template-columns: 0 1fr;
    gap: 0;
}

/* Sidebar */
.sidebar {
    background: var(--surface-color);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 1.5rem;
    height: fit-content;
    position: sticky;
    top: 2rem;
    box-shadow: var(--shadow-lg);
    transition: all var(--transition-base);
    opacity: 0.95;
}

.sidebar.collapsed {
    width: 0 !important;
    min-width: 0 !important;
    padding: 0 !important;
    margin: 0 !important;
    overflow: hidden;
    opacity: 0;
    transform: translateX(-100%);
    border: none;
    box-shadow: none;
}

/* Sidebar collapsed styles moved above */

.nav-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
}

.nav-header h2 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
}

.btn-collapse {
    background: transparent;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 0.5rem;
    border-radius: var(--border-radius-sm);
    transition: all var(--transition-fast);
}

.btn-collapse:hover {
    background: var(--surface-light);
    color: var(--text-primary);
}

.module-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.module-list li {
    position: relative;
}

.module-list a {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 1rem;
    color: var(--text-secondary);
    text-decoration: none;
    border-radius: var(--border-radius);
    transition: all var(--transition-fast);
    position: relative;
    overflow: hidden;
    font-weight: 500;
}

.module-list a::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    height: 100%;
    width: 3px;
    background: var(--primary-color);
    transform: scaleY(0);
    transition: transform var(--transition-fast);
}

.module-list a:hover {
    background: var(--surface-light);
    color: var(--text-primary);
    transform: translateX(4px);
}

.module-list a:hover::before {
    transform: scaleY(1);
}

.module-list a.active {
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.2), rgba(139, 92, 246, 0.2));
    color: var(--primary-light);
    border: 1px solid rgba(99, 102, 241, 0.3);
}

.module-list a.active::before {
    transform: scaleY(1);
}

.module-list a.completed {
    position: relative;
}

.module-list a.completed::after {
    content: "✓";
    position: absolute;
    right: 1rem;
    color: var(--success-color);
    font-weight: 700;
    font-size: 1.1rem;
}

.module-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    background: var(--surface-lighter);
    border-radius: 50%;
    font-size: 0.875rem;
    font-weight: 600;
    flex-shrink: 0;
}

.module-list a.active .module-number {
    background: var(--primary-color);
    color: white;
}

.module-list a.completed .module-number {
    background: var(--success-color);
    color: white;
}

.sidebar-footer {
    margin-top: 2rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}

.achievement-preview h3 {
    font-size: 1rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.achievement-badges {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.achievement-badge {
    font-size: 1.5rem;
    padding: 0.5rem;
    background: var(--surface-light);
    border-radius: var(--border-radius-sm);
    transition: transform var(--transition-fast);
    cursor: pointer;
}

.achievement-badge:hover {
    transform: scale(1.1);
}

.achievement-badge.locked {
    opacity: 0.3;
    filter: grayscale(100%);
}

/* Course Content */
.course-content {
    background: var(--surface-color);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 3rem;
    box-shadow: var(--shadow-lg);
    min-height: 700px;
    width: 100%;
    max-width: 100%;
    box-sizing: border-box;
    overflow-x: hidden;
    opacity: 0.95;
}

.module {
    animation: fadeInContent 0.4s ease-out;
}

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

.module h2 {
    font-size: 2.5rem;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
    font-weight: 800;
    line-height: 1.2;
}

.module h3 {
    font-size: 1.75rem;
    margin-top: 2.5rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
    font-weight: 700;
    padding-bottom: 0.75rem;
    border-bottom: 3px solid var(--primary-color);
    position: relative;
}

.module h3::after {
    content: '';
    position: absolute;
    bottom: -3px;
    left: 0;
    width: 60px;
    height: 3px;
    background: var(--accent-color);
}

.module h4 {
    font-size: 1.25rem;
    margin-top: 1.5rem;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
    font-weight: 600;
}

.module p {
    margin-bottom: 1.25rem;
    color: var(--text-secondary);
    line-height: 1.8;
    font-size: 1.05rem;
}

.module ul, .module ol {
    margin-left: 1.5rem;
    margin-bottom: 1.5rem;
    color: var(--text-secondary);
}

.module li {
    margin-bottom: 0.75rem;
    line-height: 1.7;
}

.module strong {
    color: var(--text-primary);
    font-weight: 600;
}

/* Code Blocks */
.code-block {
    background: var(--code-bg-color, #1a1a2e);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    margin: 1.5rem 0;
    overflow-x: auto;
    position: relative;
    box-shadow: var(--shadow);
    width: 100%;
    max-width: 100%;
    box-sizing: border-box;
}

.code-block::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: linear-gradient(90deg, var(--primary-color), var(--secondary-color));
}

.code-block pre {
    margin: 0;
    font-family: 'JetBrains Mono', 'Courier New', monospace;
    font-size: 0.95rem;
    color: var(--code-text-color, #a78bfa);
    line-height: 1.6;
    max-width: 100%;
    overflow-x: auto;
    word-wrap: break-word;
    overflow-wrap: break-word;
}

.copy-btn {
    position: absolute;
    top: 0.75rem;
    right: 0.75rem;
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    font-size: 0.875rem;
    font-weight: 600;
    transition: all var(--transition-fast);
    z-index: 10;
}

.copy-btn:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.4);
}

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

/* Info Boxes */
.example-box, .tip-box, .warning-box, .info-box {
    border-radius: var(--border-radius);
    padding: 1.5rem;
    margin: 1.5rem 0;
    border-left: 4px solid;
    position: relative;
    overflow: hidden;
}

.example-box::before, .tip-box::before, .warning-box::before, .info-box::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 0.05;
    pointer-events: none;
}

.example-box {
    background: rgba(99, 102, 241, 0.1);
    border-left-color: var(--primary-color);
}

.example-box h4 {
    color: var(--primary-light);
    margin-top: 0;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.tip-box {
    background: rgba(16, 185, 129, 0.1);
    border-left-color: var(--success-color);
}

.tip-box h4 {
    color: var(--success-color);
    margin-top: 0;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.warning-box {
    background: rgba(245, 158, 11, 0.1);
    border-left-color: var(--warning-color);
}

.warning-box h4 {
    color: var(--warning-color);
    margin-top: 0;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.info-box {
    background: rgba(59, 130, 246, 0.1);
    border-left-color: var(--info-color);
}

.info-box h4 {
    color: var(--info-color);
    margin-top: 0;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Exercise Box */
.exercise-box {
    background: var(--surface-light);
    border: 2px solid var(--primary-color);
    border-radius: var(--border-radius-lg);
    padding: 2rem;
    margin: 2rem 0;
    box-shadow: var(--shadow-lg);
    transition: all var(--transition-base);
}

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

.exercise-box h4 {
    color: var(--primary-light);
    margin-top: 0;
    font-size: 1.3rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

/* Interactive Elements */
    .interactive-input {
        width: 100%;
        max-width: 100%;
        background: var(--bg-color);
        border: 2px solid var(--border-color);
        border-radius: var(--border-radius);
        padding: 1rem;
        color: var(--text-primary);
        font-family: 'JetBrains Mono', monospace;
        font-size: 0.95rem;
        margin: 1rem 0;
        resize: vertical;
        min-height: 120px;
        transition: all var(--transition-fast);
        box-sizing: border-box;
    }

.interactive-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.code-playground {
    background: var(--surface-light);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 1.5rem;
    margin: 1.5rem 0;
}

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

.playground-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
}

.playground-actions {
    display: flex;
    gap: 0.5rem;
}

.playground-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

.playground-input, .playground-output {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.playground-label {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-tertiary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.playground-textarea {
    width: 100%;
    max-width: 100%;
    min-height: 200px;
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 1rem;
    color: var(--text-primary);
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.9rem;
    resize: vertical;
    box-sizing: border-box;
}

.playground-textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}

.playground-result {
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 1rem;
    min-height: 200px;
    color: var(--text-secondary);
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.9rem;
    white-space: pre-wrap;
}

/* Quiz */
.quiz-container {
    background: var(--surface-light);
    border-radius: var(--border-radius-lg);
    padding: 2rem;
    margin: 2rem 0;
}

.quiz-question {
    margin-bottom: 2rem;
    padding-bottom: 2rem;
    border-bottom: 1px solid var(--border-color);
}

.quiz-question:last-child {
    border-bottom: none;
    margin-bottom: 0;
    padding-bottom: 0;
}

.quiz-question h4 {
    color: var(--text-primary);
    margin-bottom: 1rem;
    font-size: 1.15rem;
    margin-top: 0;
}

.quiz-options {
    list-style: none;
    margin-left: 0;
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.quiz-option {
    background: var(--surface-color);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 1rem 1.25rem;
    cursor: pointer;
    transition: all var(--transition-fast);
    position: relative;
    overflow: hidden;
}

.quiz-option::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    height: 100%;
    width: 4px;
    background: var(--primary-color);
    transform: scaleY(0);
    transition: transform var(--transition-fast);
}

.quiz-option:hover {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
    transform: translateX(4px);
}

.quiz-option:hover::before {
    transform: scaleY(1);
}

.quiz-option.selected {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.2);
}

.quiz-option.correct {
    border-color: var(--success-color);
    background: rgba(16, 185, 129, 0.2);
    animation: correctPulse 0.5s ease-out;
}

.quiz-option.incorrect {
    border-color: var(--danger-color);
    background: rgba(239, 68, 68, 0.2);
    animation: shake 0.5s ease-out;
}

@keyframes correctPulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.02); }
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-10px); }
    75% { transform: translateX(10px); }
}

.quiz-feedback {
    margin-top: 1rem;
    padding: 1rem;
    border-radius: var(--border-radius);
    display: none;
    font-weight: 500;
}

.quiz-feedback.show {
    display: block;
    animation: slideIn 0.3s ease-out;
}

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

.quiz-feedback.correct {
    background: rgba(16, 185, 129, 0.2);
    color: var(--success-color);
    border: 1px solid var(--success-color);
}

.quiz-feedback.incorrect {
    background: rgba(239, 68, 68, 0.2);
    color: var(--danger-color);
    border: 1px solid var(--danger-color);
}

/* Buttons */
.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    font-family: inherit;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    box-shadow: var(--shadow);
}

.btn-primary:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 8px 16px rgba(99, 102, 241, 0.4);
}

.btn-primary:active:not(:disabled) {
    transform: translateY(0);
}

.btn-secondary {
    background: var(--surface-light);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
}

.btn-secondary:hover:not(:disabled) {
    background: var(--surface-lighter);
    border-color: var(--primary-color);
    transform: translateY(-2px);
}

.btn-icon {
    padding: 0.75rem;
    background: var(--surface-light);
    border: 1px solid var(--border-color);
    aspect-ratio: 1;
    display: inline-flex;
    align-items: center;
    justify-content: center;
}

.btn-icon:hover:not(:disabled) {
    background: var(--surface-lighter);
    border-color: var(--primary-color);
    transform: translateY(-2px);
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none !important;
}

.btn-icon-left, .btn-icon-right {
    font-size: 1.2rem;
}

.btn-sm {
    padding: 0.5rem 1rem;
    font-size: 0.875rem;
}

/* Controls */
.controls {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
    margin-top: 2rem;
    animation: fadeIn 0.6s ease-out 0.6s both;
}

/* Module Metadata */
.module-metadata {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
}

.module-duration {
    color: var(--text-tertiary);
    font-size: 0.9rem;
    font-weight: 500;
}

/* Exercise Feedback */
.exercise-feedback {
    margin-top: 1rem;
    padding: 1rem 1.25rem;
    border-radius: var(--border-radius);
    font-size: 0.95rem;
    line-height: 1.6;
    display: none;
    animation: slideIn 0.3s ease-out;
}

.exercise-feedback.show {
    display: block;
}

/* Quiz Score */
.quiz-score {
    background: var(--surface-light);
    border: 2px solid var(--primary-color);
    border-radius: var(--border-radius-lg);
    padding: 2rem;
    margin: 2rem 0;
    text-align: center;
    animation: scaleIn 0.4s ease-out;
}

.quiz-score h3 {
    font-size: 2rem;
    color: var(--primary-light);
    margin-bottom: 1rem;
    margin-top: 0;
}

.quiz-score p {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

/* Badges */
.badge {
    display: inline-block;
    padding: 0.35rem 0.85rem;
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

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

.badge-intermediate {
    background: rgba(245, 158, 11, 0.2);
    color: var(--warning-color);
    border: 1px solid var(--warning-color);
}

.badge-advanced {
    background: rgba(239, 68, 68, 0.2);
    color: var(--danger-color);
    border: 1px solid var(--danger-color);
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.8);
    backdrop-filter: blur(10px);
    animation: fadeIn 0.3s ease-out;
}

[data-theme="light"] .modal {
    background: rgba(0, 0, 0, 0.5);
}

.modal.show {
    display: flex;
    align-items: center;
    justify-content: center;
}

.modal-content {
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-lg);
    padding: 2.5rem;
    max-width: 90%;
    max-height: 90%;
    overflow-y: auto;
    position: relative;
    box-shadow: var(--shadow-xl);
    animation: scaleIn 0.3s ease-out;
}

@keyframes scaleIn {
    from {
        opacity: 0;
        transform: scale(0.9);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

.modal-close {
    position: absolute;
    top: 1rem;
    right: 1rem;
    background: var(--surface-light);
    border: none;
    color: var(--text-primary);
    font-size: 2rem;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.modal-close:hover {
    background: var(--danger-color);
    transform: rotate(90deg);
}

/* Achievement Modal */
.achievement-modal {
    max-width: 800px;
}

.achievement-modal h2 {
    margin-bottom: 2rem;
    font-size: 2rem;
}

.achievements-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 1.5rem;
}

.achievement-card {
    background: var(--surface-light);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    text-align: center;
    transition: all var(--transition-base);
}

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

.achievement-card.unlocked {
    border-color: var(--success-color);
}

.achievement-card.locked {
    opacity: 0.5;
    filter: grayscale(100%);
}

.achievement-icon {
    font-size: 3rem;
    margin-bottom: 0.5rem;
}

.achievement-title {
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.achievement-description {
    font-size: 0.875rem;
    color: var(--text-tertiary);
}

/* Certificate */
.certificate-modal {
    max-width: 900px;
}

.certificate {
    background: white;
    color: #1a1a2e;
    padding: 3rem;
    margin-bottom: 2rem;
}

.certificate-border {
    border: 8px double #6366f1;
    padding: 2rem;
    position: relative;
}

.certificate-border::before,
.certificate-border::after {
    content: '';
    position: absolute;
    width: 50px;
    height: 50px;
    border: 4px solid #8b5cf6;
}

.certificate-border::before {
    top: -4px;
    left: -4px;
    border-right: none;
    border-bottom: none;
}

.certificate-border::after {
    bottom: -4px;
    right: -4px;
    border-left: none;
    border-top: none;
}

.certificate-header {
    text-align: center;
    margin-bottom: 2rem;
}

.certificate-header h1 {
    font-size: 2.5rem;
    color: #6366f1;
    margin-bottom: 1rem;
}

.certificate-icon {
    font-size: 4rem;
}

.certificate-body {
    text-align: center;
    margin: 2rem 0;
}

.certificate-text {
    font-size: 1.1rem;
    color: #64748b;
    margin: 0.5rem 0;
}

.certificate-name {
    font-size: 2.5rem;
    color: #1a1a2e;
    margin: 1rem 0;
    font-weight: 700;
    border-bottom: 2px solid #6366f1;
    display: inline-block;
    padding-bottom: 0.5rem;
}

.certificate-course {
    font-size: 1.5rem;
    color: #6366f1;
    margin: 1rem 0;
}

.certificate-date, .certificate-id {
    font-size: 0.95rem;
    color: #64748b;
    margin: 0.5rem 0;
}

.certificate-footer {
    margin-top: 3rem;
    display: flex;
    justify-content: center;
}

.signature {
    text-align: center;
}

.signature-line {
    width: 200px;
    height: 2px;
    background: #1a1a2e;
    margin-bottom: 0.5rem;
}

.signature p {
    font-size: 0.9rem;
    color: #64748b;
}

.certificate-actions {
    display: flex;
    gap: 1rem;
    align-items: center;
    flex-wrap: wrap;
}

.name-input {
    flex: 1;
    min-width: 200px;
    padding: 0.75rem 1rem;
    background: var(--surface-light);
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    color: var(--text-primary);
    font-size: 1rem;
}

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

/* Toast Notification */
.toast {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 1rem 1.5rem;
    box-shadow: var(--shadow-xl);
    transform: translateY(200px);
    opacity: 0;
    transition: all var(--transition-base);
    z-index: 2000;
    max-width: 400px;
}

.toast.show {
    transform: translateY(0);
    opacity: 1;
}

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

.toast.error {
    border-left: 4px solid var(--danger-color);
}

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

/* Mobile Menu Button */
    .mobile-menu-btn {
        display: none;
        background: var(--surface-light);
        border: 1px solid var(--border-color);
        border-radius: var(--border-radius-sm);
        padding: 0.75rem;
        cursor: pointer;
        color: var(--text-primary);
        font-size: 1.5rem;
        transition: all var(--transition-fast);
        min-width: 48px;
        min-height: 48px;
        touch-action: manipulation;
        -webkit-tap-highlight-color: transparent;
    }

    .mobile-menu-btn:hover {
        background: var(--surface-lighter);
        border-color: var(--primary-color);
    }

    .mobile-menu-btn.active {
        background: var(--primary-color);
        color: white;
    }
    
    .mobile-menu-btn:active {
        transform: scale(0.95);
    }

/* Responsive Design */
@media (max-width: 1200px) {
    .main-content {
        grid-template-columns: 280px 1fr;
    }
}

@media (max-width: 968px) {
    body {
        overflow-x: hidden;
        width: 100%;
        max-width: 100vw;
    }
    
    body.menu-open {
        touch-action: none;
    }
    
    .container {
        padding: 0.875rem;
        max-width: 100%;
        width: 100%;
        box-sizing: border-box;
        overflow-x: hidden;
    }

    .main-content {
        grid-template-columns: 1fr;
        gap: 1rem;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
        overflow-x: hidden;
    }
    
    /* Ensure all content respects container width */
    .main-content > * {
        max-width: 100%;
        box-sizing: border-box;
    }

    .mobile-menu-btn {
        display: inline-flex;
        align-items: center;
        justify-content: center;
    }

    .sidebar {
        position: fixed;
        top: 0;
        left: -100%;
        width: 320px;
        max-width: 85vw;
        height: 100vh;
        height: 100dvh; /* Dynamic viewport height for mobile */
        z-index: 1100;
        margin: 0;
        border-radius: 0;
        border-left: none;
        border-top: none;
        border-bottom: none;
        border-right: 2px solid var(--border-color);
        transition: left var(--transition-base);
        overflow-y: auto;
        overflow-x: hidden;
        box-shadow: var(--shadow-xl);
        -webkit-overflow-scrolling: touch;
        overscroll-behavior-y: contain;
        overscroll-behavior-x: none;
        /* Ensure smooth scrolling */
        scroll-behavior: smooth;
    }

    .sidebar.mobile-open {
        left: 0;
    }
    
    /* Visual feedback for scrollable sidebar content */
    .sidebar::after {
        content: '';
        position: sticky;
        bottom: 0;
        left: 0;
        right: 0;
        height: 20px;
        background: linear-gradient(to top, var(--surface-color), transparent);
        pointer-events: none;
        z-index: 10;
    }
    
    body.menu-open {
        overflow: hidden;
        position: fixed;
        width: 100%;
        height: 100vh;
    }


    .header-content {
        flex-wrap: wrap;
        gap: 0.75rem;
        padding: 1rem 1.25rem;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }

    .logo-section {
        flex: 1;
        min-width: 0;
        overflow: hidden;
        gap: 1rem;
    }
    
    .logo-section h1 {
        overflow: hidden;
        text-overflow: ellipsis;
        white-space: nowrap;
    }
    
    .logo-icon {
        font-size: 2.5rem;
    }

    .header-actions {
        flex-wrap: wrap;
        gap: 0.5rem;
        align-items: center;
    }
    
    .header-actions .btn {
        flex-shrink: 0;
    }
    
    .header-actions .btn-icon {
        min-width: 44px;
        min-height: 44px;
        padding: 0.625rem;
    }

    .main-header h1 {
        font-size: 1.35rem;
    }

    .subtitle {
        font-size: 0.85rem;
    }

    .course-content {
        padding: 1.25rem;
        min-height: auto;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
        overflow-x: hidden;
    }
    
    .module {
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
        overflow-wrap: break-word;
        word-wrap: break-word;
    }

    .module h2 {
        font-size: 1.5rem;
        line-height: 1.3;
        margin-bottom: 1rem;
    }

    .module h3 {
        font-size: 1.35rem;
        margin-top: 1.5rem;
        margin-bottom: 0.75rem;
    }

    .module h4 {
        font-size: 1.1rem;
        margin-top: 1rem;
        margin-bottom: 0.5rem;
    }

    .module p {
        font-size: 0.95rem;
        line-height: 1.6;
        margin-bottom: 1rem;
    }
    
    .module ul, .module ol {
        margin-left: 1.25rem;
        margin-bottom: 1rem;
    }
    
    .module li {
        margin-bottom: 0.5rem;
        line-height: 1.5;
    }

    .progress-container {
        padding: 1.25rem;
        margin-bottom: 1.25rem;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }

    .progress-header {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.875rem;
    }

    .progress-text {
        font-size: 1.1rem;
        font-weight: 700;
    }

    .stats {
        width: 100%;
        justify-content: space-between;
        gap: 0.5rem;
        flex-wrap: wrap;
    }

    .stat-item {
        flex: 1;
        min-width: 0;
        min-width: calc(33.333% - 0.5rem);
        padding: 0.25rem;
    }

    .stat-value {
        font-size: 1.1rem;
        font-weight: 700;
    }

    .stat-label {
        font-size: 0.65rem;
        line-height: 1.2;
        text-align: center;
    }
    
    .progress-bar {
        margin-top: 0.875rem;
        height: 16px;
    }

    .playground-content {
        grid-template-columns: 1fr;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }
    
    .playground-input, .playground-output {
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }
    
    .playground-textarea {
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }

    .controls {
        flex-wrap: nowrap;
        gap: 0.5rem;
        padding: 0.75rem;
        margin-top: 1.5rem;
        justify-content: space-between;
        align-items: center;
    }

    .controls #resetBtn {
        order: 2;
    }

    .controls #nextBtn {
        order: 3;
    }

    .btn {
        padding: 0.625rem 1rem;
        font-size: 0.875rem;
        min-height: 40px; /* Touch target size */
    }

    .controls .btn-icon {
        min-width: 36px;
        min-height: 36px;
        max-width: 44px;
        max-height: 44px;
        padding: 0.5rem;
        font-size: 0.95rem;
        flex: 0 0 auto;
    }

    .code-block {
        padding: 0.875rem;
        margin: 1rem 0;
        font-size: 0.8rem;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }

    .code-block pre {
        font-size: 0.8rem;
        line-height: 1.5;
        max-width: 100%;
        overflow-x: auto;
        word-break: break-word;
    }

    .copy-btn {
        padding: 0.5rem 0.75rem;
        font-size: 0.75rem;
        min-height: 32px;
    }

    .example-box, .tip-box, .warning-box, .info-box {
        padding: 1rem;
        margin: 1rem 0;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }
    
    .example-box h4, .tip-box h4, .warning-box h4, .info-box h4 {
        font-size: 1rem;
        margin-bottom: 0.5rem;
    }

    .exercise-box {
        padding: 1.25rem;
        margin: 1.25rem 0;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }
    
    .exercise-box h4 {
        font-size: 1.15rem;
        margin-bottom: 0.75rem;
    }

    .quiz-container {
        padding: 1.25rem;
        margin: 1.25rem 0;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }
    
    .quiz-question {
        margin-bottom: 1.25rem;
        padding-bottom: 1.25rem;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }
    
    .quiz-question h4 {
        font-size: 1.05rem;
        margin-bottom: 0.75rem;
    }

    .quiz-option {
        padding: 0.875rem;
        min-height: 44px; /* Touch-friendly */
        display: flex;
        align-items: center;
        font-size: 0.9rem;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }

    .module-list a {
        padding: 1rem;
        min-height: 52px; /* Touch-friendly - larger target */
        display: flex;
        align-items: center;
        touch-action: manipulation;
        -webkit-tap-highlight-color: rgba(99, 102, 241, 0.2);
    }
    
    .module-list {
        padding-right: 0.5rem; /* Space for scrollbar if needed */
    }

    .toast {
        bottom: 1rem;
        right: 1rem;
        left: 1rem;
        max-width: none;
        padding: 1rem;
    }
}

@media (max-width: 640px) {
    body {
        overflow-x: hidden;
        width: 100%;
        max-width: 100vw;
    }
    
    .container {
        padding: 0.75rem;
        max-width: 100%;
        width: 100%;
        box-sizing: border-box;
        overflow-x: hidden;
    }
    
    /* Prevent any element from exceeding viewport width */
    * {
        max-width: 100%;
    }
    
    img, video, iframe, embed, object {
        max-width: 100%;
        height: auto;
    }

    .main-header {
        margin-bottom: 0.875rem;
    }

    .header-content {
        padding: 0.875rem 1rem;
    }

    .main-header h1 {
        font-size: 1.25rem;
    }

    .subtitle {
        font-size: 0.85rem;
    }

    .logo-icon {
        font-size: 2rem;
    }

    .progress-container {
        padding: 1rem;
        margin-bottom: 0.875rem;
    }

    .progress-text {
        font-size: 1.1rem;
    }

    .stats {
        gap: 0.5rem;
    }

    .stat-value {
        font-size: 1.1rem;
    }

    .stat-label {
        font-size: 0.65rem;
    }

    .course-content {
        padding: 1rem;
    }

    .module h2 {
        font-size: 1.5rem;
        margin-bottom: 1rem;
    }

    .module h3 {
        font-size: 1.35rem;
        margin-top: 1.5rem;
    }

    .module h4 {
        font-size: 1.1rem;
    }

    .module p {
        font-size: 0.95rem;
        margin-bottom: 1rem;
    }

    .module ul, .module ol {
        margin-left: 1.25rem;
        margin-bottom: 1rem;
    }

    .module li {
        margin-bottom: 0.5rem;
    }

    .code-block {
        padding: 0.875rem;
        margin: 1rem 0;
    }

    .code-block pre {
        font-size: 0.8rem;
    }

    .example-box, .tip-box, .warning-box, .info-box {
        padding: 1rem;
        margin: 1rem 0;
    }

    .exercise-box {
        padding: 1.25rem;
        margin: 1.25rem 0;
    }

    .exercise-box h4 {
        font-size: 1.15rem;
    }

    .quiz-container {
        padding: 1.25rem;
    }

    .quiz-question {
        margin-bottom: 1.5rem;
        padding-bottom: 1.5rem;
    }

    .quiz-question h4 {
        font-size: 1.05rem;
    }

    .quiz-option {
        padding: 0.875rem;
    }

    .interactive-input {
        padding: 0.875rem;
        font-size: 0.9rem;
        min-height: 100px;
    }

    .playground-textarea {
        min-height: 150px;
        padding: 0.875rem;
        font-size: 0.85rem;
    }

    .playground-result {
        padding: 0.875rem;
        min-height: 150px;
        font-size: 0.85rem;
    }

    .controls {
        margin-top: 1.25rem;
        padding: 0.625rem;
        gap: 0.5rem;
    }

    .btn {
        padding: 0.625rem 0.875rem;
        font-size: 0.85rem;
        min-height: 40px;
    }
    
    .controls .btn-icon {
        min-width: 36px;
        min-height: 36px;
        max-width: 42px;
        max-height: 42px;
        padding: 0.45rem;
        font-size: 0.9rem;
        flex: 0 0 auto;
    }

    .achievements-grid {
        grid-template-columns: 1fr;
        gap: 1rem;
    }

    .achievement-card {
        padding: 1.25rem;
    }

    .achievement-icon {
        font-size: 2.5rem;
    }

    .certificate {
        padding: 1.25rem;
    }

    .certificate-border {
        padding: 1rem;
    }

    .certificate-header h1 {
        font-size: 1.5rem;
    }

    .certificate-name {
        font-size: 1.5rem;
    }

    .certificate-course {
        font-size: 1.25rem;
    }

    .certificate-actions {
        flex-direction: column;
    }

    .name-input {
        width: 100%;
        min-width: auto;
    }

    .modal-content {
        padding: 1.25rem;
        max-width: 95%;
        margin: 1rem;
    }

    .modal-close {
        width: 36px;
        height: 36px;
        font-size: 1.75rem;
        top: 0.75rem;
        right: 0.75rem;
    }

    .sidebar {
        width: 280px;
    }

    .nav-header h2 {
        font-size: 1.1rem;
    }

    .module-list a {
        padding: 0.875rem;
        font-size: 0.9rem;
    }

    .module-number {
        width: 24px;
        height: 24px;
        font-size: 0.8rem;
    }
}

/* Touch device optimizations */
@media (hover: none) and (pointer: coarse) {
    .btn:hover {
        transform: none;
    }

    .btn:active {
        transform: scale(0.96);
        opacity: 0.85;
        transition: transform 0.1s, opacity 0.1s;
    }

    .module-list a:hover {
        transform: none;
    }

    .module-list a:active {
        transform: translateX(4px);
        background: rgba(99, 102, 241, 0.2);
    }

    .quiz-option:hover {
        transform: none;
    }

    .quiz-option:active {
        transform: scale(0.98);
        background: rgba(99, 102, 241, 0.2);
    }
    
    /* Better touch feedback */
    .btn-icon:active {
        transform: scale(0.95);
        background: var(--primary-color);
    }
    
    .copy-btn:active {
        transform: scale(0.9);
    }
    
    /* Prevent text selection on tap */
    .btn,
    .btn-icon,
    .quiz-option,
    .module-list a {
        -webkit-user-select: none;
        user-select: none;
        -webkit-touch-callout: none;
    }
}

/* Landscape mobile optimizations */
@media (max-width: 968px) and (orientation: landscape) {
    .sidebar {
        width: 300px;
    }

    .course-content {
        padding: 1rem;
    }

    .module h2 {
        font-size: 1.5rem;
    }
}

/* Scrollbar Styling */
::-webkit-scrollbar {
    width: 12px;
    height: 12px;
}

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

::-webkit-scrollbar-thumb {
    background: var(--surface-lighter);
    border-radius: 6px;
}

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

/* Selection */
::selection {
    background: rgba(99, 102, 241, 0.3);
    color: var(--text-primary);
}

/* Mobile-specific improvements */
@media (max-width: 968px) {
    /* Improve tap highlight */
    * {
        -webkit-tap-highlight-color: rgba(99, 102, 241, 0.2);
    }
    
    /* Better scrolling on iOS */
    .sidebar,
    .course-content,
    .modal-content {
        -webkit-overflow-scrolling: touch;
    }
    
    /* Prevent zoom on input focus (iOS) */
    input[type="text"],
    textarea {
        font-size: 16px !important;
    }
    
    /* Improve button touch targets */
    .btn,
    .btn-icon,
    .quiz-option,
    .module-list a {
        touch-action: manipulation;
    }
    
    /* Safe area support for notched devices */
    .container {
        padding-left: max(1rem, env(safe-area-inset-left));
        padding-right: max(1rem, env(safe-area-inset-right));
    }
    
    /* Better header layout */
    .header-content {
        padding: 1rem 1.25rem;
    }
    
    .logo-section {
        gap: 1rem;
    }
    
    .logo-icon {
        font-size: 2.5rem;
    }
    
    /* Better progress visibility */
    .progress-bar {
        height: 20px;
        margin-top: 1rem;
    }
    
    .progress-fill {
        box-shadow: 0 0 15px rgba(99, 102, 241, 0.4);
    }
    
    /* Improved code block scrolling */
    .code-block {
        position: relative;
        border-radius: var(--border-radius);
        margin: 1.5rem 0;
        -webkit-overflow-scrolling: touch;
        overscroll-behavior-x: contain;
        scrollbar-width: thin;
    }
    
    .code-block::after {
        content: '→';
        position: absolute;
        right: 0.5rem;
        top: 50%;
        transform: translateY(-50%);
        color: var(--text-tertiary);
        font-size: 1.5rem;
        pointer-events: none;
        opacity: 0.5;
        display: none; /* Hide on mobile, show scrollbar instead */
    }
    
    .code-block::-webkit-scrollbar {
        height: 6px;
    }
    
    .code-block::-webkit-scrollbar-thumb {
        background: var(--primary-color);
        border-radius: 3px;
    }
    
    .code-block::-webkit-scrollbar-track {
        background: var(--surface-light);
        border-radius: 3px;
    }
    
    /* Better button spacing */
    .header-actions {
        gap: 0.75rem;
    }
    
    .header-actions .btn-icon {
        min-width: 48px;
        min-height: 48px;
        font-size: 1.25rem;
    }
    
    /* Improved module list */
    .module-list a {
        font-size: 0.95rem;
        padding: 1.125rem 1rem;
    }
    
    /* Better content spacing */
    .module {
        word-wrap: break-word;
        overflow-wrap: break-word;
    }
    
    .module p {
        word-break: break-word;
    }
    
    /* Improved exercise boxes */
    .exercise-box {
        border-width: 2px;
    }
    
    /* Better quiz options */
    .quiz-option {
        font-size: 0.95rem;
        line-height: 1.5;
    }
    
    /* Improved controls layout */
    .controls {
        position: sticky;
        bottom: 0;
        background: var(--bg-color);
        padding: 0.75rem;
        padding-bottom: max(0.75rem, env(safe-area-inset-bottom));
        margin: 0 -1rem -1rem;
        border-top: 1px solid var(--border-color);
        z-index: 10;
        box-shadow: 0 -4px 12px rgba(0, 0, 0, 0.3);
        backdrop-filter: blur(10px);
        -webkit-backdrop-filter: blur(10px);
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }
    
    /* Better modal experience */
    .modal-content {
        margin: 0.5rem;
        max-height: calc(100vh - 1rem);
        border-radius: var(--border-radius-lg);
    }
    
    /* Improved playground */
    .playground-header {
        flex-wrap: wrap;
        gap: 0.75rem;
    }
    
    .playground-actions {
        width: 100%;
        justify-content: flex-end;
    }
    
    /* Better certificate on mobile */
    .certificate {
        transform: scale(0.95);
        transform-origin: top center;
    }
}

/* Enhanced mobile experience for small screens */
@media (max-width: 640px) {
    /* Better container padding */
    .container {
        padding: 0.5rem;
        padding-left: max(0.5rem, env(safe-area-inset-left));
        padding-right: max(0.5rem, env(safe-area-inset-right));
        padding-top: max(0.5rem, env(safe-area-inset-top));
    }
    
    /* Compact header */
    .header-content {
        padding: 0.875rem 1rem;
        padding-top: max(0.875rem, env(safe-area-inset-top));
        gap: 0.75rem;
    }
    
    .logo-section {
        gap: 0.75rem;
    }
    
    .logo-icon {
        font-size: 2rem;
    }
    
    .main-header h1 {
        font-size: 1.15rem;
        line-height: 1.2;
    }
    
    .subtitle {
        font-size: 0.8rem;
        line-height: 1.3;
    }
    
    /* Compact header actions */
    .header-actions {
        gap: 0.5rem;
    }
    
    .header-actions .btn-icon {
        min-width: 44px;
        min-height: 44px;
        padding: 0.625rem;
        font-size: 1.1rem;
    }
    
    /* Better progress display */
    .progress-container {
        padding: 1rem;
        margin-bottom: 0.75rem;
    }
    
    .progress-header {
        gap: 0.75rem;
    }
    
    .progress-text {
        font-size: 1rem;
    }
    
    .stats {
        gap: 0.25rem;
    }
    
    .stat-item {
        padding: 0.5rem 0.25rem;
    }
    
    .stat-value {
        font-size: 1rem;
    }
    
    .stat-label {
        font-size: 0.6rem;
        line-height: 1.2;
    }
    
    /* Better content area */
    .course-content {
        padding: 1rem;
        border-radius: var(--border-radius);
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
        overflow-x: hidden;
    }
    
    .module {
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
        overflow-wrap: break-word;
        word-wrap: break-word;
    }
    
    .module * {
        max-width: 100%;
        box-sizing: border-box;
    }
    
    /* Improved typography */
    .module h2 {
        font-size: 1.25rem;
        line-height: 1.3;
        margin-bottom: 0.75rem;
    }
    
    .module h3 {
        font-size: 1.15rem;
        margin-top: 1.25rem;
        margin-bottom: 0.75rem;
        padding-bottom: 0.5rem;
    }
    
    .module h4 {
        font-size: 1rem;
        margin-top: 1rem;
        margin-bottom: 0.5rem;
    }
    
    .module p {
        font-size: 0.875rem;
        line-height: 1.6;
        margin-bottom: 0.75rem;
    }
    
    .module ul, .module ol {
        margin-left: 1rem;
        margin-bottom: 0.75rem;
    }
    
    .module li {
        margin-bottom: 0.5rem;
        line-height: 1.5;
    }
    
    /* Better code blocks */
    .code-block {
        padding: 0.75rem;
        margin: 0.875rem 0;
        border-radius: var(--border-radius-sm);
        position: relative;
    }
    
    .code-block pre {
        font-size: 0.75rem;
        line-height: 1.5;
        word-break: break-all;
        overflow-wrap: break-word;
    }
    
    .copy-btn {
        padding: 0.5rem 0.625rem;
        font-size: 0.7rem;
        min-height: 32px;
        min-width: 32px;
        top: 0.5rem;
        right: 0.5rem;
        touch-action: manipulation;
        z-index: 2;
    }
    
    /* Compact info boxes */
    .example-box, .tip-box, .warning-box, .info-box {
        padding: 0.875rem;
        margin: 0.875rem 0;
        border-left-width: 3px;
    }
    
    .example-box h4, .tip-box h4, .warning-box h4, .info-box h4 {
        font-size: 0.95rem;
        margin-bottom: 0.5rem;
    }
    
    /* Better exercise boxes */
    .exercise-box {
        padding: 1rem;
        margin: 0.875rem 0;
    }
    
    .exercise-box h4 {
        font-size: 1.05rem;
        margin-bottom: 0.75rem;
    }
    
    /* Improved quiz */
    .quiz-container {
        padding: 1rem;
        margin: 0.875rem 0;
    }
    
    .quiz-question {
        margin-bottom: 1rem;
        padding-bottom: 1rem;
    }
    
    .quiz-question h4 {
        font-size: 0.95rem;
        line-height: 1.4;
        margin-bottom: 0.75rem;
    }
    
    .quiz-option {
        padding: 0.75rem;
        font-size: 0.875rem;
        min-height: 44px;
    }
    
    /* Better inputs */
    .interactive-input {
        padding: 0.75rem;
        font-size: 16px; /* Prevent zoom on iOS */
        min-height: 120px;
        border-radius: var(--border-radius-sm);
        -webkit-appearance: none;
        appearance: none;
        touch-action: manipulation;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }
    
    .playground-textarea {
        min-height: 140px;
        padding: 0.75rem;
        font-size: 16px; /* Prevent zoom on iOS */
        -webkit-appearance: none;
        appearance: none;
        touch-action: manipulation;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
    }
    
    .playground-result {
        padding: 0.75rem;
        min-height: 140px;
        font-size: 0.8rem;
        line-height: 1.5;
        overflow-y: auto;
        -webkit-overflow-scrolling: touch;
        width: 100%;
        max-width: 100%;
        box-sizing: border-box;
        word-wrap: break-word;
        overflow-wrap: break-word;
    }
    
    /* Better controls */
    .controls {
        padding: 0.625rem 0.5rem;
        padding-bottom: max(0.625rem, env(safe-area-inset-bottom));
        gap: 0.375rem;
        margin: 0 -0.5rem -0.5rem;
    }
    
    
    .controls .btn-primary,
    .controls .btn-secondary {
        padding: 0.625rem 0.875rem;
        font-size: 0.8rem;
        min-height: 40px;
        flex: 1;
        min-width: 0;
        touch-action: manipulation;
    }
    
    .btn {
        padding: 0.625rem 0.875rem;
        font-size: 0.8rem;
        min-height: 40px;
        touch-action: manipulation;
    }
    
    .controls .btn-icon {
        min-width: 36px;
        min-height: 36px;
        max-width: 40px;
        max-height: 40px;
        padding: 0.45rem;
        font-size: 0.85rem;
        touch-action: manipulation;
        flex: 0 0 auto;
    }
    
    /* Better button spacing on very small screens */
    .controls .btn-primary,
    .controls .btn-secondary {
        font-weight: 600;
        letter-spacing: 0.025em;
    }
    
    /* Better modals */
    .modal-content {
        padding: 1rem;
        max-width: calc(100vw - 1rem);
        margin: 0.5rem;
        max-height: calc(100vh - 1rem);
    }
    
    .modal-close {
        width: 40px;
        height: 40px;
        font-size: 1.5rem;
        top: 0.5rem;
        right: 0.5rem;
    }
    
    /* Better sidebar */
    .sidebar {
        width: 85vw;
        max-width: 320px;
        padding: 1.25rem;
        padding-top: max(1.25rem, env(safe-area-inset-top));
        padding-bottom: max(1.25rem, env(safe-area-inset-bottom));
    }
    
    .nav-header {
        margin-bottom: 1rem;
        padding-bottom: 0.75rem;
    }
    
    .nav-header h2 {
        font-size: 1rem;
        user-select: none;
    }
    
    .btn-collapse {
        min-width: 40px;
        min-height: 40px;
        touch-action: manipulation;
        display: flex;
        align-items: center;
        justify-content: center;
    }
    
    .module-list a {
        padding: 1rem 0.875rem;
        font-size: 0.9rem;
        gap: 0.75rem;
        min-height: 52px;
    }
    
    .module-number {
        width: 28px;
        height: 28px;
        font-size: 0.8rem;
    }
    
    /* Better toast */
    .toast {
        bottom: max(1rem, env(safe-area-inset-bottom));
        left: 0.5rem;
        right: 0.5rem;
        padding: 0.875rem;
        font-size: 0.9rem;
        max-width: calc(100vw - 1rem);
        box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
    }
    
    /* Better certificate */
    .certificate {
        padding: 1rem;
        transform: scale(0.9);
    }
    
    .certificate-border {
        padding: 0.75rem;
    }
    
    .certificate-header h1 {
        font-size: 1.25rem;
    }
    
    .certificate-name {
        font-size: 1.25rem;
    }
    
    .certificate-course {
        font-size: 1.1rem;
    }
    
    .certificate-actions {
        gap: 0.75rem;
    }
    
    .name-input {
        padding: 0.75rem;
        font-size: 16px; /* Prevent zoom on iOS */
        -webkit-appearance: none;
        appearance: none;
        touch-action: manipulation;
    }
    
    /* Better achievements */
    .achievement-card {
        padding: 1rem;
    }
    
    .achievement-icon {
        font-size: 2rem;
    }
    
    .achievement-title {
        font-size: 0.9rem;
    }
    
    .achievement-description {
        font-size: 0.8rem;
    }
}

/* Very small screens */
@media (max-width: 375px) {
    .container {
        padding: 0.375rem;
    }
    
    .header-content {
        padding: 0.75rem;
    }
    
    .main-header h1 {
        font-size: 1rem;
    }
    
    .logo-icon {
        font-size: 1.75rem;
    }
    
    .progress-container {
        padding: 0.875rem;
    }
    
    .course-content {
        padding: 0.875rem;
    }
    
    .btn {
        padding: 0.625rem 0.875rem;
        font-size: 0.85rem;
    }
}

/* Landscape mobile optimizations */
@media (max-width: 968px) and (orientation: landscape) {
    .sidebar {
        width: 320px;
    }
    
    .course-content {
        padding: 1rem;
    }
    
    .module h2 {
        font-size: 1.5rem;
    }
    
    .controls {
        position: relative;
        margin: 1rem 0 0;
    }
    
    /* Reduce header height in landscape */
    .header-content {
        padding: 0.75rem 1rem;
    }
    
    .main-header h1 {
        font-size: 1.2rem;
    }
    
    .logo-icon {
        font-size: 2rem;
    }
}

/* Improved touch feedback */
@media (hover: none) and (pointer: coarse) {
    .btn:active {
        transform: scale(0.96);
        opacity: 0.85;
    }
    
    .btn-icon:active {
        transform: scale(0.95);
    }
    
    .module-list a:active {
        background: var(--primary-color);
        color: white;
        transform: scale(0.98);
    }
    
    .quiz-option:active {
        background: rgba(99, 102, 241, 0.3);
        transform: scale(0.98);
    }
    
    .copy-btn:active {
        transform: scale(0.95);
    }
}

/* Better scrolling indicators */
@media (max-width: 968px) {
    .code-block {
        scrollbar-width: thin;
        scrollbar-color: var(--primary-color) var(--surface-light);
    }
    
    .code-block::-webkit-scrollbar {
        height: 6px;
    }
    
    .code-block::-webkit-scrollbar-thumb {
        background: var(--primary-color);
        border-radius: 3px;
    }
    
    .code-block::-webkit-scrollbar-track {
        background: var(--surface-light);
        border-radius: 3px;
    }
    
    /* Add scroll hint for code blocks */
    .code-block {
        position: relative;
    }
    
    .code-block pre {
        overflow-x: auto;
        padding-right: 1rem;
    }
    
    /* Visual indicator for scrollable content */
    .code-block::before {
        content: '';
        position: absolute;
        right: 0;
        top: 0;
        bottom: 0;
        width: 20px;
        background: linear-gradient(to right, transparent, rgba(30, 41, 59, 0.8));
        pointer-events: none;
        z-index: 1;
    }
}

/* Performance optimizations for mobile */
@media (max-width: 968px) {
    .animated-bg {
        opacity: 0.3;
    }
    
    .gradient-orb {
        filter: blur(60px);
        opacity: 0.15;
        animation-duration: 30s !important;
    }
    
    /* Reduce animations on mobile for better performance */
    /* Only speed up UI transitions, not decorative animations */
    .module,
    .btn,
    .modal,
    .sidebar {
        transition-duration: 0.2s !important;
    }
    
    /* Keep decorative animations at slower speeds */
    .logo-icon {
        animation-duration: 4s !important;
    }
    
    .progress-glow {
        animation-duration: 3s !important;
    }
    
    /* Optimize rendering */
    .container,
    .main-content,
    .course-content {
        will-change: auto;
        transform: translateZ(0);
    }
    
    /* Improve scrolling performance */
    body {
        -webkit-overflow-scrolling: touch;
        overscroll-behavior-y: contain;
    }
    
    /* Reduce repaints */
    .progress-fill,
    .progress-glow {
        will-change: width;
    }
    
    /* Optimize modal animations */
    .modal-content {
        will-change: transform, opacity;
    }
}