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

/* CSS Reset */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* CSS Variables */
:root {
    /* Colors */
    --color-primary: #2563eb;
    --color-primary-dark: #1d4ed8;
    --color-secondary: #10b981;
    --color-text: #1f2937;
    --color-text-light: #6b7280;
    --color-bg: #ffffff;
    --color-bg-alt: #f9fafb;
    --color-border: #e5e7eb;
    
    /* Typography */
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    --font-size-base: 16px;
    --font-size-sm: 14px;
    --font-size-lg: 18px;
    --font-size-xl: 24px;
    --font-size-2xl: 32px;
    --font-size-3xl: 48px;
    
    /* 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: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-full: 9999px;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 300ms ease;
}

/* Base Styles */
html {
    font-size: var(--font-size-base);
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    color: var(--color-text);
    background-color: var(--color-bg);
    line-height: 1.6;
}

/* ============================================
   Typography
   ============================================ */

h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
}

h1 { font-size: var(--font-size-3xl); }
h2 { font-size: var(--font-size-2xl); }
h3 { font-size: var(--font-size-xl); }

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

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

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

/* ============================================
   Layout
   ============================================ */

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

/* ============================================
   Header & Navigation
   ============================================ */

.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background-color: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    z-index: 1000;
}

.nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) var(--spacing-md);
    max-width: 1200px;
    margin: 0 auto;
}

.nav-brand a {
    font-size: var(--font-size-lg);
    font-weight: 700;
    color: var(--color-text);
}

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

.nav-links {
    display: flex;
    list-style: none;
    gap: var(--spacing-md);
}

.nav-links a {
    color: var(--color-text);
    font-weight: 500;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    transition: background-color var(--transition-fast), color var(--transition-fast);
}

.nav-links a:hover {
    background-color: var(--color-bg-alt);
    color: var(--color-primary);
}

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

.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: var(--spacing-2xl) var(--spacing-md);
    background: linear-gradient(135deg, var(--color-bg) 0%, var(--color-bg-alt) 100%);
    margin-top: 60px; /* Header height */
}

.hero-content {
    max-width: 800px;
}

.hero h1 {
    margin-bottom: var(--spacing-md);
    color: var(--color-text);
}

.hero p {
    font-size: var(--font-size-lg);
    color: var(--color-text-light);
    margin-bottom: var(--spacing-lg);
}

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

.btn {
    display: inline-block;
    padding: var(--spacing-sm) var(--spacing-lg);
    font-size: var(--font-size-base);
    font-weight: 600;
    text-align: center;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: background-color var(--transition-fast), transform var(--transition-fast);
}

.btn:hover {
    transform: translateY(-2px);
}

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

.btn-primary:hover {
    background-color: var(--color-primary-dark);
    color: white;
}

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

.about,
.features,
.contact {
    padding: var(--spacing-2xl) var(--spacing-md);
}

.about {
    background-color: var(--color-bg);
}

.features {
    background-color: var(--color-bg-alt);
}

.contact {
    background-color: var(--color-bg);
}

.about h2,
.features h2,
.contact h2 {
    text-align: center;
    margin-bottom: var(--spacing-lg);
}

.about p {
    text-align: center;
    max-width: 600px;
    margin: 0 auto;
    color: var(--color-text-light);
}

/* ============================================
   Features Grid
   ============================================ */

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-lg);
    max-width: 1000px;
    margin: 0 auto;
}

.feature-card {
    background-color: var(--color-bg);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    text-align: center;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
}

.feature-icon {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-sm);
}

.feature-card h3 {
    margin-bottom: var(--spacing-xs);
}

.feature-card p {
    color: var(--color-text-light);
    margin-bottom: 0;
}

/* ============================================
   Contact Section
   ============================================ */

.contact p {
    text-align: center;
    margin-bottom: var(--spacing-xs);
}

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

.footer {
    background-color: var(--color-text);
    color: var(--color-bg);
    padding: var(--spacing-lg) var(--spacing-md);
    text-align: center;
}

.footer p {
    margin-bottom: 0;
}

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

@media (max-width: 768px) {
    .nav {
        flex-direction: column;
        gap: var(--spacing-sm);
    }
    
    .nav-links {
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .hero {
        padding: var(--spacing-xl) var(--spacing-sm);
    }
    
    .hero h1 {
        font-size: var(--font-size-2xl);
    }
    
    .hero p {
        font-size: var(--font-size-base);
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .nav-links {
        gap: var(--spacing-xs);
    }
    
    .nav-links a {
        padding: var(--spacing-xs);
        font-size: var(--font-size-sm);
    }
    
    .hero h1 {
        font-size: var(--font-size-xl);
    }
}