/* ============================================
   CSS VARIABLES FOR THEME MANAGEMENT
   ============================================ */
:root {
    /* Light Mode Colors */
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-card: #ffffff;
    --text-primary: #1a1a1a;
    --text-secondary: #4a5568;
    --text-muted: #718096;
    --accent-primary: #2563eb;
    --accent-secondary: #3b82f6;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.15);
    
    /* Spacing & Layout */
    --nav-height: 70px;
    --container-max: 1200px;
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 2rem;
    --spacing-lg: 4rem;
    --spacing-xl: 6rem;
    
    /* Typography */
    --font-primary: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    --font-mono: 'SF Mono', 'Monaco', 'Inconsolata', 'Fira Code', monospace;
}

/* Dark Mode Variables */
[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-card: #1e293b;
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    --accent-primary: #3b82f6;
    --accent-secondary: #60a5fa;
    --border-color: #334155;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.5);
}

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

html {
    scroll-behavior: smooth;
    overflow-x: hidden;
}

body {
    font-family: var(--font-primary);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color 0.3s ease, color 0.3s ease;
}

/* ============================================
   NAVIGATION BAR
   ============================================ */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--nav-height);
    background-color: var(--bg-card);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    transition: all 0.3s ease;
    box-shadow: var(--shadow-sm);
}

.nav-container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 var(--spacing-md);
    height: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent-primary);
    text-decoration: none;
    font-family: var(--font-mono);
}

.nav-menu {
    display: flex;
    list-style: none;
    align-items: center;
    gap: var(--spacing-md);
}

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.2s ease;
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--accent-primary);
    transition: width 0.3s ease;
}

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

.nav-link:hover::after {
    width: 100%;
}

.theme-toggle {
    background: transparent;
    border: 2px solid var(--border-color);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    transition: all 0.3s ease;
}

.theme-toggle:hover {
    border-color: var(--accent-primary);
    transform: rotate(20deg);
}

/* ============================================
   HERO SECTION
   ============================================ */
.hero {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    padding: var(--spacing-xl) var(--spacing-md);
    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
    position: relative;
}

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

.hero-title {
    font-size: 4rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    background: linear-gradient(135deg, var(--accent-primary), var(--accent-secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.5rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    font-weight: 500;
}

.hero-description {
    font-size: 1.1rem;
    color: var(--text-muted);
    margin-bottom: var(--spacing-lg);
}

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

.btn {
    padding: 0.875rem 2rem;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s ease;
    display: inline-block;
    border: 2px solid transparent;
}

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

.btn-primary:hover {
    background-color: var(--accent-secondary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

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

.btn-secondary:hover {
    background-color: var(--accent-primary);
    color: white;
    transform: translateY(-2px);
}

.scroll-indicator {
    position: absolute;
    bottom: 2rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-muted);
    font-size: 0.9rem;
}

.scroll-arrow {
    animation: bounce 2s infinite;
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        transform: translateY(0);
    }
    40% {
        transform: translateY(-10px);
    }
    60% {
        transform: translateY(-5px);
    }
}

/* ============================================
   SECTION STYLES
   ============================================ */
.section {
    padding: var(--spacing-xl) var(--spacing-md);
    background-color: var(--bg-primary);
}

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

.container {
    max-width: var(--container-max);
    margin: 0 auto;
}

.section-title {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: var(--spacing-lg);
    text-align: center;
    color: var(--text-primary);
}

/* ============================================
   ABOUT SECTION
   ============================================ */
.about-content {
    display: grid;
    gap: var(--spacing-lg);
}

.about-text {
    font-size: 1.1rem;
    color: var(--text-secondary);
    line-height: 1.8;
}

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

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

.stat-card {
    background-color: var(--bg-card);
    padding: var(--spacing-md);
    border-radius: 12px;
    text-align: center;
    border: 1px solid var(--border-color);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

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

.stat-number {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--accent-primary);
    font-family: var(--font-mono);
}

.stat-label {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-top: var(--spacing-xs);
}

/* ============================================
   PROJECTS SECTION
   ============================================ */
.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: var(--spacing-md);
}

.project-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: var(--spacing-md);
    transition: all 0.3s ease;
}

.project-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-lg);
    border-color: var(--accent-primary);
}

.project-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: var(--spacing-sm);
}

.project-title {
    font-size: 1.4rem;
    font-weight: 600;
    color: var(--text-primary);
    flex: 1;
}

.project-tag {
    background-color: var(--accent-primary);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 600;
    white-space: nowrap;
}

.project-description {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    line-height: 1.7;
}

.project-tech {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
    margin-top: var(--spacing-sm);
}

.tech-badge {
    background-color: var(--bg-secondary);
    color: var(--text-secondary);
    padding: 0.375rem 0.75rem;
    border-radius: 6px;
    font-size: 0.85rem;
    border: 1px solid var(--border-color);
    font-family: var(--font-mono);
}

/* ============================================
   SKILLS SECTION
   ============================================ */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--spacing-md);
}

.skill-category {
    background-color: var(--bg-card);
    padding: var(--spacing-md);
    border-radius: 12px;
    border: 1px solid var(--border-color);
}

.skill-category-title {
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--accent-primary);
}

.skill-list {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
}

.skill-item {
    background-color: var(--bg-secondary);
    color: var(--text-secondary);
    padding: 0.5rem 1rem;
    border-radius: 8px;
    font-size: 0.9rem;
    border: 1px solid var(--border-color);
    transition: all 0.2s ease;
}

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

/* ============================================
   EXPERIENCE SECTION
   ============================================ */
.experience-timeline {
    max-width: 800px;
    margin: 0 auto;
}

.experience-item {
    display: grid;
    grid-template-columns: 120px 1fr;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
    position: relative;
}

.experience-item::before {
    content: '';
    position: absolute;
    left: 60px;
    top: 30px;
    bottom: -40px;
    width: 2px;
    background-color: var(--border-color);
}

.experience-item:last-child::before {
    display: none;
}

.experience-date {
    color: var(--accent-primary);
    font-weight: 600;
    font-family: var(--font-mono);
    position: relative;
}

.experience-date::after {
    content: '';
    position: absolute;
    right: -22px;
    top: 5px;
    width: 12px;
    height: 12px;
    background-color: var(--accent-primary);
    border-radius: 50%;
    border: 3px solid var(--bg-primary);
}

.experience-content {
    background-color: var(--bg-card);
    padding: var(--spacing-md);
    border-radius: 12px;
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

.experience-content:hover {
    border-color: var(--accent-primary);
    box-shadow: var(--shadow-md);
}

.experience-title {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    color: var(--text-primary);
}

.experience-company {
    color: var(--accent-primary);
    font-size: 1rem;
    margin-bottom: var(--spacing-sm);
}

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

/* ============================================
   CONTACT SECTION
   ============================================ */
.contact-content {
    max-width: 600px;
    margin: 0 auto;
    text-align: center;
}

.contact-text {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
    line-height: 1.8;
}

.contact-methods {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.contact-link {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    text-decoration: none;
    color: var(--text-primary);
    transition: all 0.3s ease;
}

.contact-link:hover {
    border-color: var(--accent-primary);
    background-color: var(--accent-primary);
    color: white;
    transform: translateX(5px);
}

.contact-icon {
    font-size: 1.5rem;
}

/* ============================================
   FOOTER
   ============================================ */
.footer {
    background-color: var(--bg-secondary);
    padding: var(--spacing-md);
    text-align: center;
    color: var(--text-muted);
    border-top: 1px solid var(--border-color);
}

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

.footer-tech {
    font-size: 0.85rem;
    font-family: var(--font-mono);
}

/* ============================================
   ANIMATION CLASSES
   ============================================ */
.fade-in {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ============================================
   RESPONSIVE DESIGN
   ============================================ */
@media (max-width: 768px) {
    .nav-menu {
        gap: var(--spacing-sm);
    }
    
    .nav-link {
        font-size: 0.9rem;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-subtitle {
        font-size: 1.2rem;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .projects-grid {
        grid-template-columns: 1fr;
    }
    
    .skills-grid {
        grid-template-columns: 1fr;
    }
    
    .experience-item {
        grid-template-columns: 1fr;
        gap: var(--spacing-sm);
    }
    
    .experience-item::before {
        display: none;
    }
    
    .experience-date::after {
        display: none;
    }
    
    .hero-cta {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
    }
}

@media (max-width: 480px) {
    :root {
        --spacing-md: 1.5rem;
        --spacing-lg: 3rem;
        --spacing-xl: 4rem;
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .stat-number {
        font-size: 2rem;
    }
}