/* ==========================================
   Modern CSS with CSS Variables & Dark Mode
   ========================================== */

:root {
    /* Light mode colors */
    --color-bg: #ffffff;
    --color-bg-secondary: #f8fafc;
    --color-bg-tertiary: #f1f5f9;
    --color-text: #0f172a;
    --color-text-secondary: #475569;
    --color-text-tertiary: #64748b;
    --color-primary: #3b82f6;
    --color-primary-hover: #2563eb;
    --color-accent: #8b5cf6;
    --color-border: #e2e8f0;
    --color-card-bg: #ffffff;
    --color-shadow: rgba(0, 0, 0, 0.1);
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    
    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', 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;
    --font-size-5xl: 3rem;
    
    /* Border radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    
    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
    --color-bg: #0f172a;
    --color-bg-secondary: #1e293b;
    --color-bg-tertiary: #334155;
    --color-text: #f1f5f9;
    --color-text-secondary: #cbd5e1;
    --color-text-tertiary: #94a3b8;
    --color-primary: #60a5fa;
    --color-primary-hover: #3b82f6;
    --color-accent: #a78bfa;
    --color-border: #334155;
    --color-card-bg: #1e293b;
    --color-shadow: rgba(0, 0, 0, 0.3);
}

/* ==========================================
   Base Styles
   ========================================== */

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-text);
    background-color: var(--color-bg);
    transition: background-color var(--transition-base), color var(--transition-base);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

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

.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background-color: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    backdrop-filter: blur(10px);
    background-color: rgba(255, 255, 255, 0.8);
    transition: all var(--transition-base);
}

[data-theme="dark"] .nav {
    background-color: rgba(15, 23, 42, 0.8);
}

.nav-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 4rem;
}

.logo {
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--color-primary);
    text-decoration: none;
    letter-spacing: -0.02em;
}

.theme-toggle {
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-xs);
    border-radius: var(--radius-md);
    color: var(--color-text);
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover {
    background-color: var(--color-bg-secondary);
}

.sun-icon {
    display: block;
}

.moon-icon {
    display: none;
}

[data-theme="dark"] .sun-icon {
    display: none;
}

[data-theme="dark"] .moon-icon {
    display: block;
}

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

.hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding: var(--spacing-2xl) 0;
    overflow: hidden;
}

.hero-content {
    position: relative;
    z-index: 10;
    max-width: 800px;
    margin: 0 auto;
    text-align: center;
}

.hero-title {
    font-size: var(--font-size-5xl);
    font-weight: 700;
    line-height: 1.1;
    margin-bottom: var(--spacing-lg);
    letter-spacing: -0.03em;
}

.gradient-text {
    background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-description {
    font-size: var(--font-size-xl);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-xl);
    line-height: 1.7;
}

.hero-cta {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

.hero-grid {
    position: absolute;
    inset: 0;
    opacity: 0.1;
    background-image: 
        linear-gradient(var(--color-border) 1px, transparent 1px),
        linear-gradient(90deg, var(--color-border) 1px, transparent 1px);
    background-size: 50px 50px;
    animation: gridMove 20s linear infinite;
}

@keyframes gridMove {
    0% {
        transform: translateY(0);
    }
    100% {
        transform: translateY(50px);
    }
}

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

.btn {
    display: inline-block;
    padding: 0.875rem 1.75rem;
    font-size: var(--font-size-base);
    font-weight: 600;
    text-decoration: none;
    border-radius: var(--radius-lg);
    transition: all var(--transition-base);
    border: 2px solid transparent;
    cursor: pointer;
    white-space: nowrap;
}

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

.btn-primary:hover {
    background-color: var(--color-primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 10px 25px var(--color-shadow);
}

.btn-secondary {
    background-color: transparent;
    color: var(--color-text);
    border-color: var(--color-border);
}

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

.btn-large {
    padding: 1.125rem 2.5rem;
    font-size: var(--font-size-lg);
}

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

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

.section-title {
    font-size: var(--font-size-4xl);
    font-weight: 700;
    text-align: center;
    margin-bottom: var(--spacing-xl);
    letter-spacing: -0.02em;
}

/* ==========================================
   Features Section
   ========================================== */

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

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

.feature-card {
    background-color: var(--color-card-bg);
    padding: var(--spacing-xl);
    border-radius: var(--radius-xl);
    border: 1px solid var(--color-border);
    transition: all var(--transition-base);
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 20px 40px var(--color-shadow);
    border-color: var(--color-primary);
}

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

.feature-card h3 {
    font-size: var(--font-size-xl);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

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

/* ==========================================
   Tech Stack Section
   ========================================== */

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

.tech-item {
    background-color: var(--color-card-bg);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    text-align: center;
    transition: all var(--transition-fast);
}

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

.tech-name {
    font-size: var(--font-size-lg);
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    color: var(--color-primary);
}

.tech-desc {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
}

/* ==========================================
   Stats Section
   ========================================== */

.stats {
    background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
    color: white;
}

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

.stat-card {
    text-align: center;
    padding: var(--spacing-lg);
}

.stat-number {
    font-size: var(--font-size-4xl);
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
}

.stat-label {
    font-size: var(--font-size-lg);
    opacity: 0.9;
}

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

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

.contact-content {
    text-align: center;
    max-width: 600px;
    margin: 0 auto;
}

.contact-description {
    font-size: var(--font-size-lg);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-xl);
    line-height: 1.7;
}

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

.footer {
    background-color: var(--color-bg-tertiary);
    padding: var(--spacing-xl) 0;
    border-top: 1px solid var(--color-border);
}

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

.footer-logo {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: var(--spacing-sm);
}

.footer-text {
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
}

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

@media (max-width: 768px) {
    .hero-title {
        font-size: var(--font-size-4xl);
    }
    
    .hero-description {
        font-size: var(--font-size-lg);
    }
    
    .section-title {
        font-size: var(--font-size-3xl);
    }
    
    .features-grid,
    .tech-grid {
        grid-template-columns: 1fr;
    }
    
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: var(--font-size-3xl);
    }
    
    .hero-cta {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
        text-align: center;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
}

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

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

.hero-content,
.feature-card,
.tech-item,
.stat-card {
    animation: fadeIn var(--transition-slow) ease-out;
}

/* ==========================================
   Accessibility
   ========================================== */

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* Focus styles for keyboard navigation */
a:focus-visible,
button:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}