/* ========================================
   CSS VARIABLES FOR THEMING
   ======================================== */
:root {
    /* Primary Colors - Professional Blue Theme */
    --primary-color: #2563eb;
    --primary-dark: #1e40af;
    --primary-light: #3b82f6;
    --accent-color: #0ea5e9;
    
    /* Light Mode Colors */
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    --border-color: #e2e8f0;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --card-bg: #ffffff;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    
    /* Typography */
    --font-primary: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 2rem;
    --font-size-4xl: 2.5rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    
    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 250ms ease-in-out;
    --transition-slow: 350ms ease-in-out;
}

/* Dark Mode Colors */
@media (prefers-color-scheme: dark) {
    :root {
        --bg-primary: #0f172a;
        --bg-secondary: #1e293b;
        --bg-tertiary: #334155;
        --text-primary: #f1f5f9;
        --text-secondary: #cbd5e1;
        --text-muted: #64748b;
        --border-color: #334155;
        --shadow-color: rgba(0, 0, 0, 0.3);
        --card-bg: #1e293b;
    }
}

/* ========================================
   GLOBAL RESET & BASE STYLES
   ======================================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

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

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

/* ========================================
   HEADER & NAVIGATION
   ======================================== */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background-color: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    box-shadow: 0 1px 3px var(--shadow-color);
    transition: all var(--transition-base);
}

.header.scrolled {
    box-shadow: 0 4px 6px var(--shadow-color);
}

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

.logo {
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
    transition: color var(--transition-fast);
}

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

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

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition-fast);
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-md);
}

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

.menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: var(--font-size-2xl);
    color: var(--text-primary);
    cursor: pointer;
}

/* Mobile Navigation */
@media (max-width: 768px) {
    .menu-toggle {
        display: block;
    }
    
    .nav-menu {
        position: fixed;
        top: 70px;
        left: -100%;
        width: 100%;
        flex-direction: column;
        background-color: var(--bg-primary);
        padding: var(--spacing-lg);
        box-shadow: 0 4px 6px var(--shadow-color);
        transition: left var(--transition-base);
    }
    
    .nav-menu.active {
        left: 0;
    }
}

/* ========================================
   BUTTONS
   ======================================== */
.btn {
    display: inline-block;
    padding: var(--spacing-sm) var(--spacing-lg);
    border-radius: var(--radius-md);
    font-weight: 600;
    text-decoration: none;
    transition: all var(--transition-fast);
    cursor: pointer;
    border: none;
    font-family: inherit;
    font-size: var(--font-size-base);
}

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

.btn-primary:hover {
    background-color: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.btn-secondary {
    background-color: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

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

.btn-large {
    padding: var(--spacing-md) var(--spacing-xl);
    font-size: var(--font-size-lg);
}

/* ========================================
   CARDS
   ======================================== */
.card {
    background-color: var(--card-bg);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    box-shadow: 0 1px 3px var(--shadow-color);
    transition: all var(--transition-base);
    border: 1px solid var(--border-color);
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: 0 12px 24px var(--shadow-color);
}

.card-title {
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
}

.card-description {
    color: var(--text-secondary);
    line-height: 1.7;
}

/* ========================================
   SECTIONS
   ======================================== */
.section {
    padding: var(--spacing-2xl) var(--spacing-lg);
    max-width: 1200px;
    margin: 0 auto;
}

.section-title {
    font-size: var(--font-size-3xl);
    font-weight: 700;
    text-align: center;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.section-subtitle {
    font-size: var(--font-size-lg);
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
    max-width: 700px;
    margin-left: auto;
    margin-right: auto;
}

/* ========================================
   GRID LAYOUTS
   ======================================== */
.grid {
    display: grid;
    gap: var(--spacing-lg);
}

.grid-2 {
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.grid-3 {
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

/* ========================================
   FOOTER
   ======================================== */
.footer {
    background-color: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-xl) var(--spacing-lg);
    margin-top: var(--spacing-2xl);
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    gap: var(--spacing-xl);
}

.footer-section {
    flex: 1;
    min-width: 250px;
}

.footer-title {
    font-size: var(--font-size-lg);
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

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

.social-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background-color: var(--bg-tertiary);
    color: var(--text-primary);
    text-decoration: none;
    transition: all var(--transition-fast);
}

.social-icon:hover {
    background-color: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

.footer-bottom {
    text-align: center;
    margin-top: var(--spacing-xl);
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--border-color);
    color: var(--text-muted);
}

/* ========================================
   UTILITY CLASSES
   ======================================== */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

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

.mt-sm { margin-top: var(--spacing-sm); }
.mt-md { margin-top: var(--spacing-md); }
.mt-lg { margin-top: var(--spacing-lg); }
.mt-xl { margin-top: var(--spacing-xl); }

.mb-sm { margin-bottom: var(--spacing-sm); }
.mb-md { margin-bottom: var(--spacing-md); }
.mb-lg { margin-bottom: var(--spacing-lg); }
.mb-xl { margin-bottom: var(--spacing-xl); }

.pt-2xl { padding-top: var(--spacing-2xl); }

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

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

/* ========================================
   RESPONSIVE TYPOGRAPHY
   ======================================== */
@media (max-width: 768px) {
    .section-title {
        font-size: var(--font-size-2xl);
    }
    
    .section-subtitle {
        font-size: var(--font-size-base);
    }
}