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

:root {
    /* Color Palette */
    --primary-color: #667eea;
    --secondary-color: #764ba2;
    --accent-color: #f093fb;
    --accent-2: #4facfe;
    --dark-bg: #0f0f23;
    --darker-bg: #0a0a15;
    --light-bg: #ffffff;
    --gray-100: #f7fafc;
    --gray-200: #edf2f7;
    --gray-300: #e2e8f0;
    --gray-400: #cbd5e0;
    --gray-600: #718096;
    --gray-700: #4a5568;
    --gray-800: #2d3748;
    --gray-900: #1a202c;
    
    /* Typography */
    --font-primary: 'Inter', sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    
    /* Border Radius */
    --radius-sm: 0.5rem;
    --radius-md: 1rem;
    --radius-lg: 1.5rem;
    
    /* Shadows */
    --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    --shadow-glow: 0 0 30px rgba(102, 126, 234, 0.3);
    
    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 300ms ease-in-out;
    --transition-slow: 500ms ease-in-out;
}

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

body {
    font-family: var(--font-primary);
    line-height: 1.6;
    color: var(--gray-800);
    background-color: var(--light-bg);
    overflow-x: hidden;
}

/* ===================================
   Typography
   =================================== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--spacing-sm);
}

h1 { font-size: 3.5rem; }
h2 { font-size: 2.5rem; }
h3 { font-size: 2rem; }
h4 { font-size: 1.5rem; }
h5 { font-size: 1.25rem; }
h6 { font-size: 1rem; }

p {
    margin-bottom: var(--spacing-md);
}

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

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

code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    background-color: var(--gray-200);
    padding: 0.2rem 0.4rem;
    border-radius: 0.25rem;
    color: var(--secondary-color);
}

/* ===================================
   Container & Layout
   =================================== */
.container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

.section {
    padding: var(--spacing-2xl) 0;
}

.section-dark {
    background: linear-gradient(135deg, var(--dark-bg) 0%, var(--darker-bg) 100%);
    color: var(--gray-100);
}

.section-dark h1,
.section-dark h2,
.section-dark h3,
.section-dark h4,
.section-dark h5,
.section-dark h6 {
    color: var(--gray-100);
}

.section-dark p {
    color: var(--gray-300);
}

/* ===================================
   Navigation
   =================================== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow-md);
    z-index: 1000;
    transition: var(--transition-base);
}

.nav-container {
    max-width: 1280px;
    margin: 0 auto;
    padding: var(--spacing-sm) var(--spacing-lg);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--gray-900);
}

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

.nav-links {
    display: flex;
    gap: var(--spacing-lg);
}

.nav-link {
    color: var(--gray-700);
    font-weight: 500;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    transition: var(--transition-base);
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%) scaleX(0);
    width: 80%;
    height: 2px;
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
    transition: var(--transition-base);
}

.nav-link:hover,
.nav-link.active {
    color: var(--primary-color);
}

.nav-link:hover::after,
.nav-link.active::after {
    transform: translateX(-50%) scaleX(1);
}

.nav-link.external-link {
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: white;
    padding: var(--spacing-xs) var(--spacing-md);
    border-radius: 2rem;
}

.nav-link.external-link::after {
    display: none;
}

.nav-link.external-link:hover {
    color: white;
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.mobile-menu-btn {
    display: none;
    flex-direction: column;
    gap: 0.3rem;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
}

.mobile-menu-btn span {
    width: 25px;
    height: 3px;
    background-color: var(--gray-800);
    border-radius: 2px;
    transition: var(--transition-base);
}

/* ===================================
   Hero Section
   =================================== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    padding-top: 80px;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    opacity: 0.1;
}

.neural-network-bg {
    width: 100%;
    height: 100%;
    background-image: 
        repeating-linear-gradient(0deg, transparent, transparent 35px, rgba(255, 255, 255, 0.05) 35px, rgba(255, 255, 255, 0.05) 36px),
        repeating-linear-gradient(90deg, transparent, transparent 35px, rgba(255, 255, 255, 0.05) 35px, rgba(255, 255, 255, 0.05) 36px);
    animation: bgScroll 20s linear infinite;
}

@keyframes bgScroll {
    0% { transform: translate(0, 0); }
    100% { transform: translate(35px, 35px); }
}

.hero-content {
    position: relative;
    z-index: 1;
    text-align: center;
    color: white;
    max-width: 900px;
    padding: var(--spacing-xl);
}

.hero-title {
    font-size: 4rem;
    font-weight: 800;
    margin-bottom: var(--spacing-md);
    animation: fadeInUp 1s ease-out;
}

.gradient-text {
    background: linear-gradient(90deg, #fff, #f093fb);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-xl);
    opacity: 0.95;
    animation: fadeInUp 1s ease-out 0.2s backwards;
}

.hero-buttons {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    margin-bottom: var(--spacing-xl);
    animation: fadeInUp 1s ease-out 0.4s backwards;
}

.btn {
    padding: 1rem 2rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: all var(--transition-base);
    border: none;
    display: inline-block;
}

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

.btn-primary:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-xl);
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.2);
    color: white;
    backdrop-filter: blur(10px);
    border: 2px solid rgba(255, 255, 255, 0.3);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: translateY(-3px);
}

.hero-stats {
    display: flex;
    gap: var(--spacing-xl);
    justify-content: center;
    animation: fadeInUp 1s ease-out 0.6s backwards;
}

.stat {
    text-align: center;
}

.stat-number {
    font-size: 2.5rem;
    font-weight: 800;
    color: white;
}

.stat-label {
    font-size: 0.9rem;
    opacity: 0.9;
    text-transform: uppercase;
    letter-spacing: 1px;
}

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

/* ===================================
   Section Headers
   =================================== */
.section-header {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
}

.section-badge {
    display: inline-block;
    padding: 0.5rem 1rem;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: white;
    border-radius: 2rem;
    font-size: 0.875rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: var(--spacing-md);
}

.section-title {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
}

.section-description {
    font-size: 1.25rem;
    color: var(--gray-600);
    max-width: 700px;
    margin: 0 auto;
}

.section-dark .section-description {
    color: var(--gray-400);
}

/* ===================================
   Content Grid
   =================================== */
.content-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.content-card {
    background: white;
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: var(--transition-base);
}

.content-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

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

.content-card h3 {
    color: var(--gray-900);
    margin-bottom: var(--spacing-sm);
}

.content-card p {
    color: var(--gray-600);
}

.feature-list {
    list-style: none;
    margin-top: var(--spacing-md);
}

.feature-list li {
    padding: var(--spacing-xs) 0;
    padding-left: var(--spacing-md);
    position: relative;
    color: var(--gray-700);
}

.feature-list li::before {
    content: '→';
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: bold;
}

/* ===================================
   Topic Blocks
   =================================== */
.topic-block {
    background: rgba(255, 255, 255, 0.05);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

.section:not(.section-dark) .topic-block {
    background: white;
    border: 1px solid var(--gray-200);
}

.topic-title {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
    color: var(--gray-100);
}

.section:not(.section-dark) .topic-title {
    color: var(--gray-900);
}

.topic-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: white;
    border-radius: 50%;
    font-size: 1.5rem;
    font-weight: 800;
}

.topic-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-xl);
}

.topic-content.full-width {
    grid-template-columns: 1fr;
}

.text-content h4 {
    color: var(--accent-color);
    margin-top: var(--spacing-lg);
    margin-bottom: var(--spacing-sm);
}

.section:not(.section-dark) .text-content h4 {
    color: var(--secondary-color);
}

.detailed-list {
    list-style: none;
    margin-left: 0;
}

.detailed-list li {
    padding: var(--spacing-xs) 0;
    padding-left: var(--spacing-md);
    position: relative;
    color: var(--gray-300);
}

.section:not(.section-dark) .detailed-list li {
    color: var(--gray-700);
}

.detailed-list li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: bold;
    font-size: 1.5rem;
}

.detailed-list strong {
    color: var(--gray-100);
}

.section:not(.section-dark) .detailed-list strong {
    color: var(--gray-900);
}

/* ===================================
   Formula Boxes
   =================================== */
.formula-box {
    background: rgba(102, 126, 234, 0.1);
    border-left: 4px solid var(--primary-color);
    padding: var(--spacing-md);
    margin: var(--spacing-md) 0;
    border-radius: var(--radius-sm);
    overflow-x: auto;
    overflow-y: hidden;
}

.formula-box.small {
    padding: var(--spacing-sm);
    margin: var(--spacing-sm) 0;
}

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

.formula-box code {
    display: block;
    background: none;
    padding: var(--spacing-xs) 0;
    font-size: 1rem;
    color: var(--gray-100);
    white-space: nowrap;
    overflow-x: auto;
}

.section:not(.section-dark) .formula-box code {
    color: var(--gray-900);
}

.formula-explanation {
    font-size: 0.875rem;
    color: var(--gray-400);
    margin-top: var(--spacing-xs);
    white-space: normal;
}

.section:not(.section-dark) .formula-explanation {
    color: var(--gray-600);
}

/* Custom scrollbar for formula boxes */
.formula-box::-webkit-scrollbar {
    height: 8px;
}

.formula-box::-webkit-scrollbar-track {
    background: rgba(0, 0, 0, 0.1);
    border-radius: 4px;
}

.formula-box::-webkit-scrollbar-thumb {
    background: var(--primary-color);
    border-radius: 4px;
}

.formula-box::-webkit-scrollbar-thumb:hover {
    background: var(--secondary-color);
}

/* Scrollable indicator for mobile */
@media (max-width: 768px) {
    .formula-box {
        position: relative;
    }
    
    .formula-box::after {
        content: '⟶';
        position: absolute;
        right: 10px;
        top: 50%;
        transform: translateY(-50%);
        color: var(--primary-color);
        opacity: 0.5;
        font-size: 1.2rem;
        pointer-events: none;
        animation: slideHint 2s ease-in-out infinite;
    }
}

@keyframes slideHint {
    0%, 100% {
        transform: translateY(-50%) translateX(0);
        opacity: 0.5;
    }
    50% {
        transform: translateY(-50%) translateX(5px);
        opacity: 0.8;
    }
}

/* ===================================
   Diagrams & Visuals
   =================================== */
.diagram {
    background: rgba(0, 0, 0, 0.2);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    display: flex;
    align-items: center;
    justify-content: center;
}

.section:not(.section-dark) .diagram {
    background: var(--gray-100);
}

.perceptron-diagram {
    width: 100%;
    height: 300px;
}

.interactive-svg {
    width: 100%;
    height: 100%;
}

.pulse {
    animation: pulse 2s ease-in-out infinite;
}

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

/* ===================================
   Activation Functions
   =================================== */
.activation-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-lg);
}

.activation-card {
    background: rgba(255, 255, 255, 0.05);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-base);
}

.section:not(.section-dark) .activation-card {
    background: var(--gray-100);
    border: 1px solid var(--gray-300);
}

.activation-card:hover {
    transform: translateY(-5px);
    border-color: var(--primary-color);
}

.activation-card h4 {
    color: var(--primary-color);
    margin-bottom: var(--spacing-md);
}

.activation-card p {
    font-size: 0.875rem;
    margin-bottom: var(--spacing-xs);
}

.activation-card strong {
    color: var(--gray-100);
}

.section:not(.section-dark) .activation-card strong {
    color: var(--gray-900);
}

/* ===================================
   Info Boxes
   =================================== */
.info-box {
    background: rgba(240, 147, 251, 0.1);
    border: 1px solid var(--accent-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
}

.section:not(.section-dark) .info-box {
    background: rgba(102, 126, 234, 0.05);
}

.info-box h4 {
    color: var(--accent-color);
    margin-bottom: var(--spacing-md);
}

.info-box ul {
    list-style: none;
}

.info-box li {
    padding: var(--spacing-xs) 0;
    padding-left: var(--spacing-md);
    position: relative;
}

.info-box li::before {
    content: '▸';
    position: absolute;
    left: 0;
    color: var(--accent-color);
}

/* ===================================
   Architecture Section
   =================================== */
.architecture-layers {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-xl);
    margin-top: var(--spacing-xl);
}

.layer-card {
    text-align: center;
    padding: var(--spacing-xl);
    background: white;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: var(--transition-base);
}

.layer-card:hover {
    transform: translateY(-10px);
    box-shadow: var(--shadow-xl);
}

.layer-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto var(--spacing-md);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    font-weight: 800;
    color: white;
}

.input-layer {
    background: linear-gradient(135deg, #667eea, #764ba2);
}

.hidden-layer {
    background: linear-gradient(135deg, #f093fb, #f5576c);
}

.output-layer {
    background: linear-gradient(135deg, #4facfe, #00f2fe);
}

/* ===================================
   Forward Propagation Visual
   =================================== */
.forward-prop-visual {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-md);
    padding: var(--spacing-lg);
}

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

.step-label {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--gray-400);
    margin-bottom: var(--spacing-sm);
}

.section:not(.section-dark) .step-label {
    color: var(--gray-600);
}

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

.neuron {
    width: 60px;
    height: 60px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: 600;
    font-size: 0.875rem;
    box-shadow: var(--shadow-md);
}

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

/* ===================================
   Comparison Grid
   =================================== */
.comparison-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-lg);
}

.comparison-card {
    background: white;
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    border-top: 4px solid var(--primary-color);
}

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

.pros-cons {
    list-style: none;
    margin: var(--spacing-md) 0;
}

.pros-cons li {
    padding: var(--spacing-xs) 0;
    padding-left: var(--spacing-lg);
    position: relative;
}

.pros-cons .pro {
    color: #48bb78;
}

.pros-cons .con {
    color: #f56565;
}

/* ===================================
   Step List
   =================================== */
.step-list {
    list-style: none;
    counter-reset: step-counter;
}

.step-list li {
    counter-increment: step-counter;
    margin-bottom: var(--spacing-lg);
    padding-left: var(--spacing-xl);
    position: relative;
}

.step-list li::before {
    content: counter(step-counter);
    position: absolute;
    left: 0;
    top: 0;
    width: 30px;
    height: 30px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
}

/* ===================================
   Loss & Optimizer Grids
   =================================== */
.loss-grid,
.optimizer-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-lg);
}

.loss-card,
.optimizer-card {
    background: rgba(255, 255, 255, 0.05);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-base);
}

.section:not(.section-dark) .loss-card,
.section:not(.section-dark) .optimizer-card {
    background: white;
    border: 1px solid var(--gray-300);
}

.loss-card:hover,
.optimizer-card:hover {
    border-color: var(--primary-color);
    transform: translateY(-5px);
}

.loss-card h4,
.optimizer-card h4 {
    color: var(--accent-color);
    margin-bottom: var(--spacing-md);
}

/* ===================================
   Hyperparameters
   =================================== */
.hyperparameter-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-lg);
}

.hyperparam-card {
    background: rgba(255, 255, 255, 0.05);
    padding: var(--spacing-lg);
    border-radius: var(--radius-md);
    text-align: center;
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-base);
}

.section:not(.section-dark) .hyperparam-card {
    background: white;
    border: 1px solid var(--gray-300);
}

.hyperparam-card:hover {
    border-color: var(--primary-color);
    transform: scale(1.05);
}

.param-icon {
    width: 60px;
    height: 60px;
    margin: 0 auto var(--spacing-md);
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 700;
}

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

.hyperparam-card ul {
    text-align: left;
    font-size: 0.875rem;
}

/* ===================================
   Techniques Grid
   =================================== */
.technique-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-lg);
}

.technique-card {
    background: rgba(255, 255, 255, 0.05);
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-base);
}

.section:not(.section-dark) .technique-card {
    background: white;
    border: 1px solid var(--gray-300);
}

.technique-card:hover {
    border-color: var(--accent-color);
    transform: translateY(-5px);
}

.technique-card h4 {
    color: var(--accent-color);
    margin-bottom: var(--spacing-md);
}

/* ===================================
   Types of Neural Networks
   =================================== */
.types-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: var(--spacing-xl);
    margin-top: var(--spacing-xl);
}

.type-card {
    background: white;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    overflow: hidden;
    transition: var(--transition-base);
}

.type-card:hover {
    transform: translateY(-10px);
    box-shadow: var(--shadow-xl);
}

.type-header {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: var(--spacing-lg);
    text-align: center;
}

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

.type-header h3 {
    margin: 0;
    color: white;
}

.type-card .type-description {
    padding: var(--spacing-lg);
    border-bottom: 2px solid var(--gray-200);
}

.type-card h4 {
    color: var(--secondary-color);
    margin: var(--spacing-md) var(--spacing-lg) var(--spacing-sm);
}

.type-card ul {
    padding: 0 var(--spacing-lg) var(--spacing-md);
    color: var(--gray-700);
}

.type-formula {
    padding: var(--spacing-md) var(--spacing-lg);
    background: var(--gray-100);
    border-top: 2px solid var(--gray-200);
    font-family: var(--font-mono);
    font-size: 0.875rem;
}

/* ===================================
   Advanced Topics
   =================================== */
.advanced-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: var(--spacing-xl);
    margin-top: var(--spacing-xl);
}

.advanced-card {
    background: rgba(255, 255, 255, 0.05);
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    border: 2px solid rgba(255, 255, 255, 0.1);
    transition: var(--transition-base);
    position: relative;
    overflow: hidden;
}

.advanced-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
}

.advanced-card:hover {
    border-color: var(--primary-color);
    transform: translateY(-10px);
}

.advanced-card h3 {
    color: var(--accent-color);
    margin-bottom: var(--spacing-md);
}

.advanced-card h4 {
    color: var(--primary-color);
    font-size: 1.1rem;
    margin-top: var(--spacing-md);
}

/* ===================================
   Best Practices
   =================================== */
.practices-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.practice-card {
    background: white;
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: var(--transition-base);
    position: relative;
}

.practice-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.practice-number {
    position: absolute;
    top: -20px;
    left: 50%;
    transform: translateX(-50%);
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 800;
    box-shadow: var(--shadow-lg);
}

.practice-card h4 {
    color: var(--secondary-color);
    margin-top: var(--spacing-md);
    text-align: center;
}

.practice-card ul {
    margin-top: var(--spacing-md);
}

/* ===================================
   Footer
   =================================== */
.footer {
    background: var(--dark-bg);
    color: var(--gray-300);
    padding: var(--spacing-2xl) 0 var(--spacing-lg);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
}

.footer-section h4 {
    color: white;
    margin-bottom: var(--spacing-md);
}

.footer-logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    font-size: 1.5rem;
    font-weight: 800;
    color: white;
    margin-bottom: var(--spacing-md);
}

.footer-links {
    list-style: none;
}

.footer-links li {
    margin-bottom: var(--spacing-xs);
}

.footer-links a {
    color: var(--gray-400);
    transition: var(--transition-base);
}

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

.footer-bottom {
    text-align: center;
    padding-top: var(--spacing-lg);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

/* ===================================
   Responsive Design
   =================================== */
@media (max-width: 1024px) {
    .hero-title {
        font-size: 3rem;
    }
    
    .section-title {
        font-size: 2.5rem;
    }
    
    .topic-content {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    
    .mobile-menu-btn {
        display: flex;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-subtitle {
        font-size: 1rem;
    }
    
    .hero-buttons {
        flex-direction: column;
    }
    
    .hero-stats {
        flex-direction: column;
        gap: var(--spacing-md);
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .content-grid,
    .types-grid,
    .advanced-grid {
        grid-template-columns: 1fr;
    }
    
    .forward-prop-visual {
        flex-direction: column;
    }
    
    .arrow {
        transform: rotate(90deg);
    }
    
    /* Better formula display on tablets */
    .formula-box {
        padding: var(--spacing-md);
    }
    
    .formula-box code {
        font-size: 0.9rem;
    }
    
    /* Make cards stack better */
    .activation-grid,
    .loss-grid,
    .optimizer-grid,
    .hyperparameter-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    html {
        font-size: 14px;
    }
    
    .container {
        padding: 0 var(--spacing-sm);
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .section-title {
        font-size: 1.75rem;
    }
    
    .formula-box {
        padding: var(--spacing-sm);
    }
    
    .formula-box code {
        font-size: 0.85rem;
    }
    
    .topic-block {
        padding: var(--spacing-md);
    }
}

/* ===================================
   Utility Classes
   =================================== */
.text-center {
    text-align: center;
}

.mt-1 { margin-top: var(--spacing-xs); }
.mt-2 { margin-top: var(--spacing-sm); }
.mt-3 { margin-top: var(--spacing-md); }
.mt-4 { margin-top: var(--spacing-lg); }

.mb-1 { margin-bottom: var(--spacing-xs); }
.mb-2 { margin-bottom: var(--spacing-sm); }
.mb-3 { margin-bottom: var(--spacing-md); }
.mb-4 { margin-bottom: var(--spacing-lg); }

/* ===================================
   Scroll Animations
   =================================== */
@keyframes slideInFromLeft {
    from {
        transform: translateX(-50px);
        opacity: 0;
    }
    to {
        transform: translateX(0);
        opacity: 1;
    }
}

@keyframes slideInFromRight {
    from {
        transform: translateX(50px);
        opacity: 0;
    }
    to {
        transform: translateX(0);
        opacity: 1;
    }
}

/* Smooth scroll behavior */
html {
    scroll-padding-top: 80px;
}

/* Loading animation */
@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Gradient animation */
@keyframes gradientShift {
    0% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100% { background-position: 0% 50%; }
}