/**
 * 8gwifi.org Tutorial Platform - Design System
 * Modern, minimal, fully independent CSS
 * No Bootstrap dependencies
 */

/* ============================================
   CSS RESET & BASE
   ============================================ */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

/* ============================================
   CSS VARIABLES - DESIGN TOKENS
   ============================================ */
:root {
    /* Colors - Light Mode */
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --bg-code: #1e293b;

    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    --text-inverse: #ffffff;

    --accent-primary: #6366f1;
    --accent-hover: #4f46e5;
    --accent-light: #e0e7ff;

    --success: #10b981;
    --success-light: #d1fae5;
    --warning: #f59e0b;
    --warning-light: #fef3c7;
    --error: #ef4444;
    --error-light: #fee2e2;

    --border: #e2e8f0;
    --border-light: #f1f5f9;
    --border-focus: #6366f1;

    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);

    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', 'SF Mono', Consolas, monospace;

    --text-xs: 0.75rem;
    --text-sm: 0.875rem;
    --text-base: 1rem;
    --text-lg: 1.125rem;
    --text-xl: 1.25rem;
    --text-2xl: 1.5rem;
    --text-3xl: 1.875rem;
    --text-4xl: 2.25rem;

    --leading-tight: 1.25;
    --leading-normal: 1.5;
    --leading-relaxed: 1.75;

    /* Spacing */
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-5: 1.25rem;
    --space-6: 1.5rem;
    --space-8: 2rem;
    --space-10: 2.5rem;
    --space-12: 3rem;
    --space-16: 4rem;

    /* Layout */
    --sidebar-width: 0;
    --preview-width: 0;
    --header-height: 60px;

    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-full: 9999px;

    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.2s ease;
    --transition-slow: 0.3s ease;
}

/* Dark Mode */
[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --bg-code: #0d1117;

    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;

    --accent-primary: #818cf8;
    --accent-hover: #a5b4fc;
    --accent-light: #312e81;

    --border: #334155;
    --border-light: #1e293b;

    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.4);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.5);
}

/* ============================================
   RESPONSIVE BREAKPOINTS
   ============================================ */
@media (min-width: 768px) {
    :root {
        --preview-width: 350px;
    }
}

@media (min-width: 1200px) {
    :root {
        --sidebar-width: 260px;
        --preview-width: 400px;
    }
}

@media (min-width: 1600px) {
    :root {
        --sidebar-width: 280px;
        --preview-width: 480px;
    }
}

/* ============================================
   BASE STYLES
   ============================================ */
body {
    font-family: var(--font-sans);
    font-size: var(--text-base);
    line-height: var(--leading-relaxed);
    color: var(--text-primary);
    background: var(--bg-primary);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

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

code,
pre {
    font-family: var(--font-mono);
    font-size: var(--text-sm);
}

code {
    background: var(--bg-tertiary);
    padding: 0.125rem 0.375rem;
    border-radius: var(--radius-sm);
    color: var(--accent-primary);
}

pre {
    background: var(--bg-code);
    color: var(--text-inverse);
    padding: var(--space-4);
    border-radius: var(--radius-md);
    overflow-x: auto;
}

pre code {
    background: none;
    padding: 0;
    color: inherit;
}

/* Code example blocks - use this class instead of inline styles */
.code-example {
    background: var(--bg-code) !important;
    color: var(--text-inverse);
    padding: var(--space-4);
    border-radius: var(--radius-md);
    overflow-x: auto;
    margin: var(--space-4) 0;
}

.code-example code {
    background: none;
    padding: 0;
    color: inherit;
}

/* Smaller code examples */
.code-example-sm {
    background: var(--bg-code) !important;
    color: var(--text-inverse);
    padding: var(--space-3);
    border-radius: var(--radius-sm);
    overflow-x: auto;
    font-size: var(--text-sm);
}

.code-example-sm code {
    background: none;
    padding: 0;
    color: inherit;
    font-size: inherit;
}


/* ============================================
   LAYOUT - MAIN STRUCTURE
   ============================================ */
.tutorial-layout {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

.tutorial-main {
    display: flex;
    flex: 1;
    padding-top: var(--header-height);
}

/* Sidebar */
.tutorial-sidebar {
    position: fixed;
    top: var(--header-height);
    left: 0;
    bottom: 0;
    width: 280px;  /* Fixed width for mobile */
    max-width: 85vw;  /* Don't exceed viewport on small screens */
    background: var(--bg-secondary);
    border-right: 1px solid var(--border);
    overflow-y: auto;
    transform: translateX(-100%);
    transition: transform var(--transition-normal);
    z-index: 40;
}

.tutorial-sidebar.open {
    transform: translateX(0);
}

@media (min-width: 1200px) {
    .tutorial-sidebar {
        width: var(--sidebar-width);
        transform: translateX(0);
    }
}

/* Content Area */
.tutorial-content {
    flex: 1;
    min-width: 0;
    margin-left: 0;
    margin-right: 0;
    padding: var(--space-6);
    max-width: 100%;
}

@media (min-width: 768px) {
    .tutorial-content {
        margin-right: var(--preview-width);
        padding: var(--space-8);
    }
}

@media (min-width: 1200px) {
    .tutorial-content {
        margin-left: var(--sidebar-width);
        padding: var(--space-10) var(--space-12);
    }
}

/* Right Ad Rail - Desktop only */
.tutorial-ad-rail {
    display: none;
    position: fixed;
    top: var(--header-height);
    right: 0;
    bottom: 0;
    width: 336px;
    padding: var(--space-4);
    overflow-y: auto;
    z-index: 25;
}

@media (min-width: 1400px) {
    .tutorial-ad-rail {
        display: block;
    }

    /* Adjust content area when ad rail is visible */
    .has-ad-rail .tutorial-content {
        margin-right: 336px;
    }
}

@media (min-width: 1600px) {
    .tutorial-ad-rail {
        width: 360px;
    }

    .has-ad-rail .tutorial-content {
        margin-right: 360px;
    }
}

.ad-rail-inner {
    position: sticky;
    top: var(--space-4);
}

.ad-rail-slot {
    margin-bottom: var(--space-4);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 250px;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
}

.ad-rail-slot:empty {
    display: none;
}

/* Preview Panel */
.tutorial-preview {
    display: none;
    position: fixed;
    top: var(--header-height);
    right: 0;
    bottom: 0;
    width: var(--preview-width);
    background: var(--bg-secondary);
    border-left: 1px solid var(--border);
    z-index: 30;
}

@media (min-width: 768px) {
    .tutorial-preview {
        display: flex;
        flex-direction: column;
    }
}

.preview-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-3) var(--space-4);
    border-bottom: 1px solid var(--border);
    font-size: var(--text-sm);
    font-weight: 500;
    color: var(--text-secondary);
}

.preview-frame {
    flex: 1;
    width: 100%;
    border: none;
    background: var(--bg-primary);
}

/* ============================================
   HEADER
   ============================================ */
.tutorial-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: center;
    padding: 0 var(--space-4);
    z-index: 50;
}

.header-left {
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

.header-center {
    flex: 1;
    display: flex;
    justify-content: center;
}

.header-right {
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

/* Logo */
.logo {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    font-weight: 600;
    font-size: var(--text-lg);
    color: var(--text-primary);
}

.logo-icon {
    width: 32px;
    height: 32px;
    background: var(--accent-primary);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: 700;
    font-size: var(--text-sm);
}

.logo-text {
    display: none;
}

@media (min-width: 640px) {
    .logo-text {
        display: inline;
    }
}

/* Menu Button */
.menu-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background: none;
    border: none;
    border-radius: var(--radius-md);
    color: var(--text-primary);
    cursor: pointer;
    transition: background var(--transition-fast);
}

.menu-btn:hover {
    background: var(--bg-tertiary);
}

@media (min-width: 1200px) {
    .menu-btn {
        display: none;
    }
}

/* Progress Bar */
.header-progress {
    display: none;
    align-items: center;
    gap: var(--space-2);
    font-size: var(--text-sm);
    color: var(--text-muted);
}

@media (min-width: 640px) {
    .header-progress {
        display: flex;
    }
}

.progress-bar {
    width: 100px;
    height: 6px;
    background: var(--bg-tertiary);
    border-radius: var(--radius-full);
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--accent-primary);
    border-radius: var(--radius-full);
    transition: width var(--transition-slow);
}

/* Header Social Buttons */
.header-social {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.header-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    height: 34px;
    padding: 0 0.875rem;
    font-size: 0.8125rem;
    font-weight: 500;
    text-decoration: none;
    border: 1px solid transparent;
    border-radius: 17px;
    cursor: pointer;
    transition: all 0.2s ease;
    font-family: inherit;
    white-space: nowrap;
}

.header-btn .btn-icon {
    font-size: 0.9375rem;
    line-height: 1;
    display: flex;
    align-items: center;
    justify-content: center;
}

.header-btn .btn-icon svg {
    width: 14px;
    height: 14px;
}

/* Coffee Button - Warm, inviting */
.header-btn-coffee {
    background: #FFDD00;
    color: #000000;
    border-color: #FFDD00;
}

.header-btn-coffee:hover {
    background: #FFE333;
    border-color: #FFE333;
    box-shadow: 0 2px 8px rgba(255, 221, 0, 0.4);
}

.header-btn-coffee:active {
    transform: scale(0.98);
}

/* Twitter/X Button - Clean monochrome */
.header-btn-twitter {
    background: transparent;
    color: var(--text-primary);
    border-color: var(--border);
}

.header-btn-twitter:hover {
    background: var(--text-primary);
    color: var(--bg-primary);
    border-color: var(--text-primary);
}

.header-btn-twitter:active {
    transform: scale(0.98);
}

/* Share Button - Subtle, action-oriented */
.header-btn-share {
    background: transparent;
    color: var(--text-secondary);
    border-color: var(--border);
}

.header-btn-share:hover {
    background: var(--accent-primary);
    color: #ffffff;
    border-color: var(--accent-primary);
}

.header-btn-share:active {
    transform: scale(0.98);
}

/* Tablet: Show icons + text */
@media (max-width: 900px) {
    .header-btn {
        padding: 0 0.75rem;
        height: 32px;
        font-size: 0.75rem;
    }

    .header-btn .btn-icon {
        font-size: 0.875rem;
    }
}

/* Mobile: Icons only */
@media (max-width: 640px) {
    .header-social {
        gap: 0.375rem;
    }

    .header-btn {
        width: 32px;
        height: 32px;
        padding: 0;
        border-radius: 50%;
    }

    .header-btn .btn-text {
        display: none;
    }

    .header-btn .btn-icon {
        font-size: 1rem;
    }
}

/* Very small screens: Keep buttons but smaller */
@media (max-width: 400px) {
    .header-social {
        gap: 0.25rem;
    }

    .header-btn {
        width: 28px;
        height: 28px;
    }

    .header-btn .btn-icon {
        font-size: 0.875rem;
    }

    .header-btn .btn-icon svg {
        width: 12px;
        height: 12px;
    }
}

/* Theme Toggle */
.theme-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background: none;
    border: none;
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

/* ============================================
   SIDEBAR CONTENT
   ============================================ */
.sidebar-header {
    padding: var(--space-4);
    border-bottom: 1px solid var(--border);
}

.sidebar-title {
    font-size: var(--text-lg);
    font-weight: 600;
    color: var(--text-primary);
}

.sidebar-nav {
    padding: var(--space-4);
}

.nav-section {
    margin-bottom: var(--space-6);
}

.nav-section-title {
    font-size: var(--text-xs);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    padding: var(--space-2) var(--space-3);
    margin-bottom: var(--space-1);
}

.nav-items {
    list-style: none;
}

.nav-item {
    position: relative;
}

.nav-link {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-2) var(--space-3);
    font-size: var(--text-sm);
    color: var(--text-secondary);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

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

.nav-link.active {
    background: var(--accent-light);
    color: var(--accent-primary);
    font-weight: 500;
}

.nav-link::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%) scaleY(0);
    width: 3px;
    height: 20px;
    background: var(--accent-primary);
    border-radius: var(--radius-full);
    transition: transform var(--transition-fast);
}

.nav-link.active::before,
.nav-link:hover::before {
    transform: translateY(-50%) scaleY(1);
}

.nav-icon {
    width: 18px;
    height: 18px;
    flex-shrink: 0;
}

.nav-status {
    margin-left: auto;
    width: 16px;
    height: 16px;
    color: var(--success);
}

/* ============================================
   LESSON CONTENT
   ============================================ */
.lesson-header {
    margin-bottom: var(--space-8);
}

.breadcrumb {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    font-size: var(--text-sm);
    color: var(--text-muted);
    margin-bottom: var(--space-4);
}

.breadcrumb a {
    color: var(--text-muted);
}

.breadcrumb a:hover {
    color: var(--accent-primary);
}

.breadcrumb-separator {
    color: var(--border);
}

.lesson-title {
    font-size: var(--text-3xl);
    font-weight: 700;
    line-height: var(--leading-tight);
    color: var(--text-primary);
    margin-bottom: var(--space-4);
}

.lesson-meta {
    display: flex;
    align-items: center;
    gap: var(--space-4);
    font-size: var(--text-sm);
    color: var(--text-muted);
}

.lesson-body {
    max-width: 900px;
}

.lesson-body h2 {
    font-size: var(--text-2xl);
    font-weight: 600;
    margin-top: var(--space-10);
    margin-bottom: var(--space-4);
    color: var(--text-primary);
}

.lesson-body h3 {
    font-size: var(--text-xl);
    font-weight: 600;
    margin-top: var(--space-8);
    margin-bottom: var(--space-3);
    color: var(--text-primary);
}

.lesson-body p {
    margin-bottom: var(--space-4);
    color: var(--text-secondary);
}

.lesson-body ul,
.lesson-body ol {
    margin-bottom: var(--space-4);
    padding-left: var(--space-6);
}

.lesson-body li {
    margin-bottom: var(--space-2);
    color: var(--text-secondary);
}

/* ============================================
   CODE EDITOR
   ============================================ */
.editor-container {
    background: var(--bg-code);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-lg);
    margin: var(--space-6) 0;
}

.editor-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-3) var(--space-4);
    background: rgba(255, 255, 255, 0.05);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.editor-tabs {
    display: flex;
    gap: var(--space-1);
}

.editor-tab {
    padding: var(--space-1) var(--space-3);
    font-size: var(--text-sm);
    font-family: var(--font-mono);
    color: var(--text-muted);
    background: none;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.editor-tab:hover {
    color: var(--text-inverse);
    background: rgba(255, 255, 255, 0.1);
}

.editor-tab.active {
    color: var(--text-inverse);
    background: rgba(255, 255, 255, 0.15);
}

.editor-actions {
    display: flex;
    gap: var(--space-2);
}

.editor-body {
    min-height: 200px;
}

/* CodeMirror overrides */
.editor-body .CodeMirror {
    height: auto;
    min-height: 200px;
    font-family: var(--font-mono);
    font-size: var(--text-sm);
    line-height: 1.6;
}

/* ============================================
   BUTTONS
   ============================================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    padding: var(--space-2) var(--space-4);
    font-family: var(--font-sans);
    font-size: var(--text-sm);
    font-weight: 500;
    line-height: 1;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-sm {
    padding: var(--space-1) var(--space-3);
    font-size: var(--text-xs);
}

.btn-lg {
    padding: var(--space-3) var(--space-6);
    font-size: var(--text-base);
}

.btn-primary {
    background: var(--accent-primary);
    color: var(--text-inverse);
}

.btn-primary:hover:not(:disabled) {
    background: var(--accent-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background: var(--bg-tertiary);
    color: var(--text-primary);
    border: 1px solid var(--border);
}

.btn-secondary:hover:not(:disabled) {
    background: var(--bg-secondary);
    border-color: var(--border-focus);
}

.btn-success {
    background: var(--success);
    color: var(--text-inverse);
}

.btn-success:hover:not(:disabled) {
    filter: brightness(1.1);
}

.btn-ghost {
    background: transparent;
    color: var(--text-secondary);
}

.btn-ghost:hover:not(:disabled) {
    background: var(--bg-tertiary);
    color: var(--text-primary);
}

.btn-icon {
    width: 36px;
    height: 36px;
    padding: 0;
}

/* ============================================
   CARDS & CALLOUTS
   ============================================ */
.card {
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: var(--space-6);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-normal);
}

.card:hover {
    box-shadow: var(--shadow-md);
}

.callout {
    display: flex;
    gap: var(--space-3);
    padding: var(--space-4);
    border-radius: var(--radius-md);
    margin: var(--space-4) 0;
}

.callout-icon {
    flex-shrink: 0;
    width: 20px;
    height: 20px;
}

.callout-content {
    flex: 1;
    font-size: var(--text-sm);
}

.callout-tip {
    background: var(--success-light);
    border-left: 3px solid var(--success);
}

.callout-tip .callout-icon {
    color: var(--success);
}

.callout-warning {
    background: var(--warning-light);
    border-left: 3px solid var(--warning);
}

.callout-warning .callout-icon {
    color: var(--warning);
}

.callout-error {
    background: var(--error-light);
    border-left: 3px solid var(--error);
}

.callout-error .callout-icon {
    color: var(--error);
}

/* ============================================
   NAVIGATION (PREV/NEXT)
   ============================================ */
.lesson-nav {
    display: flex;
    justify-content: space-between;
    gap: var(--space-4);
    margin-top: var(--space-12);
    padding-top: var(--space-8);
    border-top: 1px solid var(--border);
}

.nav-prev,
.nav-next {
    flex: 1;
    max-width: 280px;
}

.nav-next {
    text-align: right;
    margin-left: auto;
}

.nav-btn {
    display: flex;
    flex-direction: column;
    gap: var(--space-1);
    padding: var(--space-4);
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    text-decoration: none;
    transition: all var(--transition-fast);
}

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

.nav-label {
    font-size: var(--text-xs);
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.nav-title {
    font-size: var(--text-base);
    font-weight: 500;
    color: var(--text-primary);
}

/* ============================================
   QUIZ COMPONENT
   ============================================ */
.quiz-container {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: var(--space-6);
    margin: var(--space-6) 0;
}

.quiz-title {
    font-size: var(--text-lg);
    font-weight: 600;
    margin-bottom: var(--space-4);
    display: flex;
    align-items: center;
    gap: var(--space-2);
}

.quiz-question {
    margin-bottom: var(--space-4);
}

.quiz-options {
    display: flex;
    flex-direction: column;
    gap: var(--space-2);
}

.quiz-option {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    padding: var(--space-3) var(--space-4);
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

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

.quiz-option.correct {
    background: var(--success-light);
    border-color: var(--success);
}

.quiz-option.incorrect {
    background: var(--error-light);
    border-color: var(--error);
}

/* ============================================
   FOOTER
   ============================================ */
.tutorial-footer {
    padding: var(--space-8) var(--space-4);
    background: var(--bg-secondary);
    border-top: 1px solid var(--border);
    margin-left: 0;
}

@media (min-width: 768px) {
    .tutorial-footer {
        margin-right: var(--preview-width);
    }
}

@media (min-width: 1200px) {
    .tutorial-footer {
        margin-left: var(--sidebar-width);
    }
}

.footer-content {
    max-width: 900px;
    margin: 0 auto;
    text-align: center;
    color: var(--text-muted);
    font-size: var(--text-sm);
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: var(--space-6);
    margin-top: var(--space-4);
}

.footer-links a {
    color: var(--text-muted);
}

.footer-links a:hover {
    color: var(--accent-primary);
}

/* ============================================
   OVERLAY (for mobile sidebar)
   ============================================ */
.overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.5);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-normal);
    z-index: 35;
}

.overlay.active {
    opacity: 1;
    visibility: visible;
}

@media (min-width: 1200px) {
    .overlay {
        display: none;
    }
}

/* ============================================
   MOBILE PREVIEW (Bottom Sheet)
   ============================================ */
.mobile-preview {
    display: none;
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--bg-primary);
    border-top: 1px solid var(--border);
    border-radius: var(--radius-xl) var(--radius-xl) 0 0;
    box-shadow: var(--shadow-xl);
    transform: translateY(100%);
    transition: transform var(--transition-normal);
    z-index: 60;
    max-height: 70vh;
    overflow: hidden;
}

.mobile-preview.open {
    transform: translateY(0);
}

@media (max-width: 767px) {
    .mobile-preview {
        display: block;
    }
}

.mobile-preview-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-4);
    border-bottom: 1px solid var(--border);
}

.mobile-preview-body {
    height: calc(70vh - 60px);
    overflow: auto;
}

/* ============================================
   UTILITY CLASSES
   ============================================ */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

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

.text-left {
    text-align: left;
}

.text-right {
    text-align: right;
}

.mt-4 {
    margin-top: var(--space-4);
}

.mt-6 {
    margin-top: var(--space-6);
}

.mt-8 {
    margin-top: var(--space-8);
}

.mb-4 {
    margin-bottom: var(--space-4);
}

.mb-6 {
    margin-bottom: var(--space-6);
}

.mb-8 {
    margin-bottom: var(--space-8);
}

.hidden {
    display: none !important;
}

/* ============================================
   ANIMATIONS
   ============================================ */
@keyframes fadeIn {
    from {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes checkmark {
    0% {
        transform: scale(0);
        opacity: 0;
    }

    50% {
        transform: scale(1.2);
    }

    100% {
        transform: scale(1);
        opacity: 1;
    }
}

.animate-fade-in {
    animation: fadeIn 0.3s ease;
}

.animate-slide-up {
    animation: slideUp 0.3s ease;
}

.animate-checkmark {
    animation: checkmark 0.3s ease-out;
}

/* Progress bar animation */
@keyframes progressFill {
    from {
        width: 0;
    }
}

.progress-fill.animate {
    animation: progressFill 0.6s ease-out;
}
/* ============================================
   EXERCISE SECTION
   ============================================ */
.exercise-section {
    background: var(--bg-secondary);
    border: 2px solid var(--accent-primary);
    border-radius: var(--radius-lg);
    padding: var(--space-6);
    margin: var(--space-6) 0;
}

[data-theme="dark"] .exercise-section {
    background: #1e1e2e;
    border-color: var(--accent-primary);
}

.exercise-section h3 {
    color: var(--accent-primary);
    margin-bottom: var(--space-4);
}

.exercise-section p {
    margin-bottom: var(--space-3);
}

.exercise-section ul {
    margin-bottom: var(--space-4);
    padding-left: var(--space-6);
}

.exercise-hint,
.exercise-solution {
    margin-top: var(--space-4);
    background: var(--bg-tertiary);
    border-radius: var(--radius-md);
    overflow: hidden;
}

[data-theme="dark"] .exercise-hint,
[data-theme="dark"] .exercise-solution {
    background: #252536;
}

.exercise-hint summary,
.exercise-solution summary {
    padding: var(--space-3) var(--space-4);
    cursor: pointer;
    font-weight: 600;
    color: var(--accent-primary);
    transition: background 0.15s ease;
}

.exercise-hint summary:hover,
.exercise-solution summary:hover {
    background: var(--bg-hover);
}

.exercise-hint pre,
.exercise-solution pre {
    margin: 0;
    padding: var(--space-4);
    background: var(--bg-code);
    color: var(--text-inverse);
    border-radius: 0;
}

.exercise-hint code,
.exercise-solution code {
    font-family: var(--font-mono);
    font-size: var(--text-sm);
}

/* ============================================
   INFO BOXES (for lessons)
   ============================================ */
.info-box, .tip-box, .warning-box, .mistake-box, .summary-box {
    padding: var(--space-4);
    margin: var(--space-4) 0;
    border-radius: var(--radius-md);
    border-left: 4px solid;
}

.info-box {
    background: var(--accent-light);
    border-color: var(--accent-primary);
    color: var(--text-primary);
}

[data-theme="dark"] .info-box {
    background: rgba(99, 102, 241, 0.15);
}

.tip-box {
    background: var(--success-light);
    border-color: var(--success);
}

[data-theme="dark"] .tip-box {
    background: rgba(16, 185, 129, 0.15);
}

.warning-box {
    background: var(--warning-light);
    border-color: var(--warning);
}

[data-theme="dark"] .warning-box {
    background: rgba(245, 158, 11, 0.15);
}

.best-practice-box {
    background: #f0fdf4;
    border-color: #16a34a;
}

[data-theme="dark"] .best-practice-box {
    background: rgba(22, 163, 74, 0.15);
}

.best-practice-box strong:first-child {
    color: #16a34a;
}

.mistake-box {
    background: var(--error-light);
    border-color: var(--error);
    margin-bottom: var(--space-3);
}

[data-theme="dark"] .mistake-box {
    background: rgba(239, 68, 68, 0.15);
}

.mistake-box h4 {
    margin: 0 0 var(--space-2) 0;
    color: var(--error);
    font-size: var(--text-sm);
}

.mistake-box pre {
    margin: 0;
    padding: var(--space-3);
    background: var(--bg-code);
    border-radius: var(--radius-sm);
    overflow-x: auto;
}

.mistake-box code {
    font-size: var(--text-sm);
    color: var(--text-inverse);
}

.summary-box {
    background: var(--bg-secondary);
    border-color: var(--accent-primary);
}

[data-theme="dark"] .summary-box {
    background: #1e1e2e;
}

.summary-box ul {
    margin: 0;
    padding-left: var(--space-5);
}

.summary-box li {
    margin-bottom: var(--space-2);
}

/* Info Table */
.info-table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--space-4) 0;
    font-size: var(--text-sm);
}

.info-table th,
.info-table td {
    padding: var(--space-3);
    text-align: left;
    border: 1px solid var(--border);
}

.info-table th {
    background: var(--bg-tertiary);
    font-weight: 600;
}

.info-table tr:nth-child(even) {
    background: var(--bg-secondary);
}

[data-theme="dark"] .info-table th {
    background: #252536;
}

[data-theme="dark"] .info-table tr:nth-child(even) {
    background: #1e1e2e;
}

/* Lead paragraph */
.lead {
    font-size: var(--text-lg);
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: var(--space-6);
}