/* ============================================
   VAE Tutorial - Modern Styling
   ============================================ */

/* ============================================
   CSS Variables & Reset
   ============================================ */

:root {
    /* Color Palette */
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary-color: #8b5cf6;
    --accent-color: #ec4899;
    
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --info-color: #3b82f6;
    
    /* Neutrals */
    --bg-color: #0f172a;
    --bg-card: #1e293b;
    --bg-elevated: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    
    /* Typography */
    --font-body: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', sans-serif;
    --font-mono: 'SF Mono', 'Monaco', 'Inconsolata', 'Fira Code', monospace;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.3);
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 350ms ease;
}

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

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

body {
    font-family: var(--font-body);
    background: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.7;
    overflow-x: hidden;
}

/* ============================================
   Navigation
   ============================================ */

.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(15, 23, 42, 0.8);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-base);
}

.navbar.scrolled {
    background: rgba(15, 23, 42, 0.95);
    box-shadow: var(--shadow-lg);
}

.nav-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand {
    font-size: 1.5rem;
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-primary);
}

.nav-icon {
    font-size: 1.75rem;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
    align-items: center;
}

.nav-menu a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition-fast);
    position: relative;
    padding: 0.5rem 0;
}

.nav-menu a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: var(--transition-base);
}

.nav-menu a:hover {
    color: var(--primary-light);
}

.nav-menu a:hover::after {
    width: 100%;
}

/* ============================================
   Hero Section
   ============================================ */

.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
    position: relative;
    overflow: hidden;
    padding: var(--spacing-2xl) var(--spacing-md);
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(circle at 20% 50%, rgba(99, 102, 241, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(236, 72, 153, 0.1) 0%, transparent 50%);
}

.hero-content {
    text-align: center;
    position: relative;
    z-index: 1;
    max-width: 900px;
}

.hero-title {
    font-size: clamp(2.5rem, 6vw, 4rem);
    font-weight: 800;
    margin-bottom: var(--spacing-md);
    background: linear-gradient(135deg, #6366f1 0%, #ec4899 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: fadeInUp 0.8s ease;
}

.hero-subtitle {
    font-size: clamp(1.125rem, 3vw, 1.5rem);
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
    animation: fadeInUp 0.8s ease 0.2s backwards;
}

.hero-badges {
    display: flex;
    gap: var(--spacing-sm);
    justify-content: center;
    flex-wrap: wrap;
    margin-bottom: var(--spacing-xl);
    animation: fadeInUp 0.8s ease 0.4s backwards;
}

.badge {
    padding: 0.5rem 1rem;
    border-radius: var(--radius-lg);
    font-size: 0.875rem;
    font-weight: 600;
}

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

.badge-secondary {
    background: rgba(139, 92, 246, 0.2);
    color: #a78bfa;
    border: 1px solid var(--secondary-color);
}

.badge-accent {
    background: rgba(236, 72, 153, 0.2);
    color: #f9a8d4;
    border: 1px solid var(--accent-color);
}

/* ============================================
   Buttons
   ============================================ */

.btn {
    display: inline-block;
    padding: 0.875rem 2rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    text-decoration: none;
    transition: all var(--transition-base);
    cursor: pointer;
    border: none;
    font-size: 1rem;
    animation: fadeInUp 0.8s ease 0.6s backwards;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.4);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(99, 102, 241, 0.5);
}

/* ============================================
   Container
   ============================================ */

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-2xl) var(--spacing-md);
}

/* ============================================
   Sections
   ============================================ */

.content-section {
    margin-bottom: var(--spacing-2xl);
    opacity: 0;
    animation: fadeIn 0.6s ease forwards;
}

.section-title {
    font-size: clamp(2rem, 4vw, 2.5rem);
    font-weight: 700;
    margin-bottom: var(--spacing-lg);
    color: var(--text-primary);
}

/* ============================================
   Cards
   ============================================ */

.content-card {
    background: var(--bg-card);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
    box-shadow: var(--shadow-md);
    border: 1px solid rgba(255, 255, 255, 0.05);
    transition: var(--transition-base);
}

.content-card:hover {
    box-shadow: var(--shadow-lg);
    border-color: rgba(99, 102, 241, 0.3);
}

.content-card h3 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-md);
    color: var(--primary-light);
}

.content-card h4 {
    font-size: 1.25rem;
    margin-top: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.content-card p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
}

.content-card ul, .content-card ol {
    margin-left: var(--spacing-lg);
    color: var(--text-secondary);
}

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

.lead {
    font-size: 1.125rem;
    font-weight: 500;
    color: var(--text-primary);
}

/* ============================================
   TOC Section
   ============================================ */

.toc-section {
    margin-bottom: var(--spacing-2xl);
}

.toc-card {
    background: linear-gradient(135deg, var(--bg-card) 0%, var(--bg-elevated) 100%);
    border-radius: var(--radius-xl);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-lg);
    border: 1px solid rgba(99, 102, 241, 0.2);
}

.toc-card h2 {
    font-size: 1.75rem;
    margin-bottom: var(--spacing-md);
    color: var(--primary-light);
}

.toc-list {
    list-style: none;
    counter-reset: toc-counter;
}

.toc-list li {
    counter-increment: toc-counter;
    margin-bottom: var(--spacing-sm);
}

.toc-list li::before {
    content: counter(toc-counter) ".";
    color: var(--primary-color);
    font-weight: 700;
    margin-right: var(--spacing-xs);
}

.toc-list a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: var(--transition-fast);
}

.toc-list a:hover {
    color: var(--primary-light);
}

/* ============================================
   Info Boxes
   ============================================ */

.info-box {
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    margin: var(--spacing-md) 0;
    border-left: 4px solid;
}

.info-box h3, .info-box h4 {
    margin-top: 0;
    margin-bottom: var(--spacing-sm);
}

.info-box ul, .info-box ol {
    margin-left: var(--spacing-lg);
}

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

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

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

/* ============================================
   Grids
   ============================================ */

.grid-2 {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-md);
    margin: var(--spacing-md) 0;
}

.grid-3 {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: var(--spacing-md);
    margin: var(--spacing-md) 0;
}

/* ============================================
   Component Cards
   ============================================ */

.component-card {
    background: var(--bg-elevated);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    text-align: center;
    transition: var(--transition-base);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.component-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(99, 102, 241, 0.3);
}

.component-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-sm);
}

.component-card h4 {
    color: var(--primary-light);
    margin-bottom: var(--spacing-xs);
}

.component-card p {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.math-inline {
    font-family: var(--font-mono);
    font-size: 0.9rem;
    color: var(--primary-light);
}

/* ============================================
   Math Blocks
   ============================================ */

.math-block {
    background: var(--bg-elevated);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    overflow-x: auto;
    margin: var(--spacing-md) 0;
    border: 1px solid rgba(99, 102, 241, 0.2);
    text-align: center;
}

.math-small {
    font-size: 0.9rem;
}

.caption {
    text-align: center;
    font-size: 0.875rem;
    color: var(--text-muted);
    font-style: italic;
    margin-top: var(--spacing-xs);
}

/* ============================================
   Loss Cards
   ============================================ */

.loss-card {
    background: var(--bg-elevated);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

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

.small-text {
    font-size: 0.875rem;
    color: var(--text-muted);
}

/* ============================================
   Architecture Diagram
   ============================================ */

.architecture-diagram {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-lg);
    background: var(--bg-elevated);
    border-radius: var(--radius-md);
    margin: var(--spacing-md) 0;
}

.arch-step {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-xs);
}

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

.arch-box {
    background: var(--bg-card);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    border: 2px solid rgba(255, 255, 255, 0.1);
    text-align: center;
    min-width: 200px;
    color: var(--text-secondary);
    font-size: 0.875rem;
    line-height: 1.6;
}

.arch-box.highlight {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
    color: var(--text-primary);
    font-weight: 600;
}

.arch-arrow {
    font-size: 2rem;
    color: var(--primary-color);
}

/* ============================================
   Parameters Grid
   ============================================ */

.params-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-sm);
    margin: var(--spacing-md) 0;
}

.param-item {
    background: var(--bg-elevated);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    display: flex;
    justify-content: space-between;
    align-items: center;
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.param-key {
    color: var(--text-muted);
    font-size: 0.875rem;
}

.param-value {
    color: var(--primary-light);
    font-weight: 600;
}

/* ============================================
   Metrics
   ============================================ */

.metrics-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-md);
    margin: var(--spacing-lg) 0;
}

.metric-card {
    background: var(--bg-elevated);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    text-align: center;
    border: 2px solid rgba(255, 255, 255, 0.05);
    transition: var(--transition-base);
}

.metric-card:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
}

.metric-value {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-light);
    margin-bottom: var(--spacing-xs);
}

.metric-label {
    font-size: 0.875rem;
    color: var(--text-muted);
}

.metric-note {
    font-size: 0.75rem;
    color: var(--success-color);
    margin-top: var(--spacing-xs);
}

.metric-improved {
    border-color: var(--success-color);
}

/* ============================================
   Images & Visualizations
   ============================================ */

.image-container {
    margin: var(--spacing-lg) 0;
}

.result-image {
    width: 100%;
    height: auto;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.image-caption {
    text-align: center;
    margin-top: var(--spacing-sm);
    font-size: 0.875rem;
    color: var(--text-muted);
    font-style: italic;
}

.slice-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
    margin: var(--spacing-md) 0;
}

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

.slice-image {
    width: 100%;
    height: auto;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.slice-label {
    margin-top: var(--spacing-sm);
    font-weight: 600;
    color: var(--primary-light);
    font-family: var(--font-mono);
}

/* ============================================
   Observations
   ============================================ */

.observations {
    background: var(--bg-elevated);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    margin-top: var(--spacing-md);
    border-left: 4px solid var(--success-color);
}

.observations h4 {
    color: var(--success-color);
    margin-top: 0;
    margin-bottom: var(--spacing-sm);
}

.observations ul {
    margin-left: var(--spacing-md);
}

/* ============================================
   Code Blocks
   ============================================ */

.code-block {
    margin: var(--spacing-md) 0;
}

.code-block h4 {
    margin-bottom: var(--spacing-sm);
    color: var(--primary-light);
}

.code-block pre {
    background: #1e1e1e;
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    overflow-x: auto;
    border: 1px solid rgba(255, 255, 255, 0.1);
    box-shadow: var(--shadow-md);
}

.code-block code {
    font-family: var(--font-mono);
    font-size: 0.875rem;
    line-height: 1.6;
}

/* ============================================
   Benefit Cards
   ============================================ */

.benefit-card {
    background: var(--bg-elevated);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    border: 1px solid rgba(255, 255, 255, 0.05);
    transition: var(--transition-base);
}

.benefit-card:hover {
    border-color: var(--primary-color);
    transform: translateX(4px);
}

.benefit-icon {
    font-size: 1.5rem;
}

.benefit-card p {
    margin: 0;
}

/* ============================================
   Change Sections
   ============================================ */

.change-section {
    margin: var(--spacing-lg) 0;
    padding: var(--spacing-md);
    background: var(--bg-elevated);
    border-radius: var(--radius-md);
    border: 1px solid rgba(255, 255, 255, 0.05);
}

.change-section h4 {
    color: var(--primary-light);
    margin-top: 0;
}

/* ============================================
   Tables
   ============================================ */

.table-container {
    overflow-x: auto;
    margin: var(--spacing-md) 0;
}

.results-table {
    width: 100%;
    border-collapse: collapse;
    background: var(--bg-elevated);
    border-radius: var(--radius-md);
    overflow: hidden;
}

.results-table thead {
    background: var(--bg-card);
}

.results-table th {
    padding: var(--spacing-md);
    text-align: left;
    color: var(--primary-light);
    font-weight: 600;
    border-bottom: 2px solid rgba(99, 102, 241, 0.3);
}

.results-table td {
    padding: var(--spacing-md);
    color: var(--text-secondary);
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
}

.results-table tbody tr {
    transition: var(--transition-fast);
}

.results-table tbody tr:hover {
    background: var(--bg-card);
}

.results-table .highlight-row {
    background: rgba(99, 102, 241, 0.1);
}

/* ============================================
   Finding Cards
   ============================================ */

.findings-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-md);
    margin: var(--spacing-md) 0;
}

.finding-card {
    background: var(--bg-elevated);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    border: 1px solid rgba(255, 255, 255, 0.05);
    transition: var(--transition-base);
}

.finding-card:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-lg);
}

.finding-card h4 {
    color: var(--primary-light);
    margin-top: 0;
    margin-bottom: var(--spacing-sm);
}

.finding-card ul {
    margin-left: var(--spacing-md);
}

/* ============================================
   Pros/Cons Cards
   ============================================ */

.pros-card, .cons-card {
    background: var(--bg-elevated);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    border: 1px solid;
}

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

.cons-card {
    border-color: var(--warning-color);
}

.pros-card h4 {
    color: var(--success-color);
}

.cons-card h4 {
    color: var(--warning-color);
}

/* ============================================
   References
   ============================================ */

.reference-list {
    list-style: none;
}

.reference-list li {
    margin-bottom: var(--spacing-sm);
    padding-left: var(--spacing-md);
    position: relative;
}

.reference-list li::before {
    content: "→";
    position: absolute;
    left: 0;
    color: var(--primary-color);
}

.reference-list a {
    color: var(--primary-light);
    text-decoration: none;
    transition: var(--transition-fast);
}

.reference-list a:hover {
    color: var(--accent-color);
    text-decoration: underline;
}

/* ============================================
   Footer
   ============================================ */

.footer {
    background: var(--bg-card);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    padding: var(--spacing-xl) var(--spacing-md);
    margin-top: var(--spacing-2xl);
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    text-align: center;
}

.footer-content p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
}

.footer-content a {
    color: var(--primary-light);
    text-decoration: none;
    transition: var(--transition-fast);
}

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

.footer-note {
    font-size: 0.875rem;
    color: var(--text-muted);
}

/* ============================================
   Animations
   ============================================ */

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

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

.fade-in {
    animation: fadeInUp 0.6s ease forwards;
}

/* ============================================
   Responsive Design
   ============================================ */

@media (max-width: 768px) {
    .nav-menu {
        gap: 1rem;
        font-size: 0.875rem;
    }
    
    .hero {
        min-height: 80vh;
        padding: var(--spacing-xl) var(--spacing-sm);
    }
    
    .container {
        padding: var(--spacing-lg) var(--spacing-sm);
    }
    
    .grid-2, .grid-3 {
        grid-template-columns: 1fr;
    }
    
    .architecture-diagram {
        padding: var(--spacing-md);
    }
    
    .arch-box {
        min-width: 150px;
        font-size: 0.75rem;
    }
    
    .results-table {
        font-size: 0.875rem;
    }
    
    .results-table th,
    .results-table td {
        padding: var(--spacing-sm);
    }
}

@media (max-width: 480px) {
    .nav-container {
        flex-direction: column;
        gap: var(--spacing-sm);
    }
    
    .nav-menu {
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .hero-badges {
        flex-direction: column;
        align-items: center;
    }
}

/* ============================================
   Print Styles
   ============================================ */

@media print {
    .navbar,
    .hero,
    .footer {
        display: none;
    }
    
    body {
        background: white;
        color: black;
    }
    
    .content-card {
        break-inside: avoid;
        box-shadow: none;
        border: 1px solid #ccc;
    }
}

/* ============================================
   Notebook Card Hover Effects
   ============================================ */

.notebook-card {
    transition: transform var(--transition-base), box-shadow var(--transition-base);
    cursor: pointer;
}

.notebook-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4), 0 0 30px rgba(99, 102, 241, 0.3);
}

.notebook-btn {
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
}

.notebook-btn::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    border-radius: 50%;
    background: rgba(99, 102, 241, 0.1);
    transform: translate(-50%, -50%);
    transition: width 0.6s, height 0.6s;
}

.notebook-btn:hover::before {
    width: 300px;
    height: 300px;
}

.notebook-btn:hover {
    transform: scale(1.05);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.3);
}