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

/* CSS Custom Properties (Variables) for consistent theming */
:root {
    --primary-color: #4f46e5;
    --secondary-color: #06b6d4;
    --accent-color: #f59e0b;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --background: #ffffff;
    --surface: #f9fafb;
    --border: #e5e7eb;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --border-radius: 0.5rem;
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
}

/* Typography */
body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--background);
}

h1, h2, h3, h4, h5, h6 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
    font-weight: 600;
}

h1 {
    font-size: 2.5rem;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-md);
}

h2 {
    font-size: 2rem;
    color: var(--primary-color);
    border-bottom: 2px solid var(--border);
    padding-bottom: var(--spacing-xs);
    margin-top: var(--spacing-lg);
}

h3 {
    font-size: 1.5rem;
    color: var(--text-primary);
}

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

/* Layout Components */
body {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-md);
}

header {
    text-align: center;
    background: linear-gradient(135deg, var(--surface) 0%, #e0e7ff 100%);
    padding: var(--spacing-xl);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    margin-bottom: var(--spacing-xl);
    border: 1px solid var(--border);
}

header h1 {
    margin-bottom: var(--spacing-xs);
}

header p {
    font-size: 1.2rem;
    color: var(--accent-color);
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

main {
    background: var(--background);
    padding: var(--spacing-xl);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    margin-bottom: var(--spacing-xl);
}

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

/* Lists */
ul, ol {
    margin-left: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
}

li {
    margin-bottom: var(--spacing-xs);
    color: var(--text-secondary);
}

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

dt {
    font-weight: 600;
    color: var(--text-primary);
    margin-top: var(--spacing-sm);
}

dd {
    margin-left: var(--spacing-md);
    color: var(--text-secondary);
}

/* Special Components */
.highlight-box {
    background: linear-gradient(135deg, #fef3c7, #fde68a);
    border: 1px solid var(--accent-color);
    border-radius: var(--border-radius);
    padding: var(--spacing-md);
    margin: var(--spacing-md) 0;
    position: relative;
}

.highlight-box::before {
    content: '💡';
    position: absolute;
    top: -25px;
    left: -15px;
    background: var(--accent-color);
    padding: var(--spacing-xs);
    border-radius: 50%;
    font-size: 1.2rem;
}

/* Grid Layouts */
.comparison-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
    margin: var(--spacing-lg) 0;
}

.comparison-item {
    background: var(--surface);
    padding: var(--spacing-md);
    border-radius: var(--border-radius);
    border: 1px solid var(--border);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.comparison-item:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 15px rgba(0, 0, 0, 0.1);
}

.features-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-md);
    margin: var(--spacing-lg) 0;
}

.feature-item {
    background: linear-gradient(135deg, var(--surface), #f0f9ff);
    padding: var(--spacing-md);
    border-radius: var(--border-radius);
    border-left: 4px solid var(--primary-color);
    transition: all 0.3s ease;
}

.feature-item:hover {
    border-left-color: var(--secondary-color);
    transform: translateX(5px);
}

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

.importance-item {
    background: var(--surface);
    padding: var(--spacing-md);
    border-radius: var(--border-radius);
    text-align: center;
    border: 1px solid var(--border);
    transition: all 0.3s ease;
}

.importance-item:hover {
    background: var(--primary-color);
    color: white;
    transform: scale(1.05);
}

.importance-item:hover h3,
.importance-item:hover p {
    color: white;
}

/* Card Components */
.concept-card {
    background: linear-gradient(135deg, #f8fafc, #e2e8f0);
    border: 1px solid var(--border);
    border-radius: var(--border-radius);
    padding: var(--spacing-md);
    margin: var(--spacing-md) 0;
    position: relative;
    overflow: hidden;
}

.concept-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: linear-gradient(to bottom, var(--primary-color), var(--secondary-color));
}

/* Animated Elements */
.animated-element {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: var(--spacing-lg);
    border-radius: var(--border-radius);
    text-align: center;
    margin: var(--spacing-lg) 0;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.animated-element::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

.animated-element:hover::before {
    left: 100%;
}

.animated-element:hover {
    transform: scale(1.02);
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.2);
}

.animated-element p {
    color: white;
    font-weight: 500;
    font-size: 1.1rem;
    margin: 0;
}

/* Quote Styling */
.css-quote {
    background: linear-gradient(135deg, #eef2ff, #ddd6fe);
    border-left: 4px solid var(--primary-color);
    padding: var(--spacing-md);
    margin: var(--spacing-lg) 0;
    border-radius: 0 var(--border-radius) var(--border-radius) 0;
    font-style: italic;
    position: relative;
}

.css-quote::before {
    font-size: 4rem;
    color: var(--primary-color);
    position: absolute;
    left: var(--spacing-md);
    opacity: 0.3;
}

blockquote p {
    color: var(--text-primary);
    font-size: 1.1rem;
}

/* Links */
a {
    color: var(--secondary-color);
    text-decoration: none;
    transition: color 0.3s ease;
    position: relative;
}

a::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--secondary-color);
    transition: width 0.3s ease;
}

a:hover::after {
    width: 100%;
}

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

/* Footer */
footer {
    text-align: center;
    padding: var(--spacing-lg);
    background: var(--surface);
    border-radius: var(--border-radius);
    border: 1px solid var(--border);
    margin-top: var(--spacing-xl);
}

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

/* Responsive Design */
@media (max-width: 768px) {
    :root {
        --spacing-xs: 0.25rem;
        --spacing-sm: 0.75rem;
        --spacing-md: 1rem;
        --spacing-lg: 1.5rem;
        --spacing-xl: 2rem;
    }
    
    body {
        padding: var(--spacing-sm);
    }
    
    h1 {
        font-size: 2rem;
    }
    
    h2 {
        font-size: 1.5rem;
    }
    
    .comparison-grid,
    .features-list {
        grid-template-columns: 1fr;
    }
    
    .importance-grid {
        grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    }
}

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

/* Apply fade-in animation to sections */
section {
    animation: fadeIn 0.6s ease-out;
}

/* Smooth scrolling */
html {
    scroll-behavior: smooth;
}