/* ============================================
   CSS VARIABLES & ROOT STYLES
   ============================================ */
:root {
    /* Light mode colors - Minimalist palette */
    --bg-primary: #ffffff;
    --bg-secondary: #fafafa;
    --text-primary: #1a1a1a;
    --text-secondary: #737373;
    --accent: #000000;
    --border: #e5e5e5;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.05);

    /* Spacing */
    --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, 'Helvetica Neue', Arial, sans-serif;
}

/* Dark mode */
[data-theme="dark"] {
    --bg-primary: #0a0a0a;
    --bg-secondary: #141414;
    --text-primary: #ededed;
    --text-secondary: #a3a3a3;
    --accent: #ffffff;
    --border: #262626;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
}

/* ============================================
   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: 1.7;
    overflow-x: hidden;
    transition: background-color 0.2s ease, color 0.2s ease;
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* ============================================
   NAVIGATION
   ============================================ */
.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    background-color: var(--bg-primary);
    border-bottom: 1px solid var(--border);
    z-index: 1000;
    transition: all 0.2s ease;
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) var(--spacing-md);
}

.logo {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--accent);
    text-decoration: none;
    letter-spacing: -0.02em;
    opacity: 0;
    transition: opacity 0.3s ease;
}

.logo.visible {
    opacity: 1;
}

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

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.9375rem;
    font-weight: 400;
    transition: color 0.2s ease;
}

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

.theme-toggle {
    background: none;
    border: 1px solid var(--border);
    border-radius: 6px;
    width: 36px;
    height: 36px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
    padding: 0;
}

.theme-toggle:hover {
    border-color: var(--accent);
}

.theme-toggle svg {
    width: 18px;
    height: 18px;
    stroke: var(--text-primary);
}

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

[data-theme="light"] .moon-icon,
:root:not([data-theme]) .moon-icon {
    display: none;
}

.mobile-menu-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
}

.mobile-menu-toggle span {
    width: 22px;
    height: 2px;
    background-color: var(--text-primary);
    transition: all 0.2s ease;
}

/* ============================================
   HERO SECTION
   ============================================ */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-xl) 0;
    background: var(--bg-primary);
}

.hero-content {
    max-width: 720px;
    animation: fadeIn 0.6s ease;
}

.hero-title {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
    line-height: 1.1;
    letter-spacing: -0.03em;
}

.highlight {
    color: var(--accent);
}

.hero-subtitle {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    font-weight: 400;
}

.hero-description {
    font-size: 1.0625rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    line-height: 1.7;
}

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

/* ============================================
   BUTTONS
   ============================================ */
.btn {
    padding: 0.75rem 1.75rem;
    border-radius: 6px;
    text-decoration: none;
    font-weight: 500;
    font-size: 0.9375rem;
    transition: all 0.2s ease;
    display: inline-block;
    border: 1px solid transparent;
}

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

.btn-primary:hover {
    opacity: 0.85;
}

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

.btn-secondary:hover {
    border-color: var(--accent);
}

/* ============================================
   SECTIONS
   ============================================ */
.section {
    padding: var(--spacing-xl) 0;
}

.section-title {
    font-size: 2rem;
    font-weight: 600;
    margin-bottom: var(--spacing-lg);
    letter-spacing: -0.02em;
}

/* ============================================
   ABOUT SECTION
   ============================================ */
.about {
    background: var(--bg-primary);
}

.about-content {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: var(--spacing-lg);
    align-items: start;
}

.about-text p {
    font-size: 1.0625rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    line-height: 1.8;
}

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

.stat {
    background: var(--bg-secondary);
    padding: var(--spacing-md);
    border-radius: 8px;
    border: 1px solid var(--border);
}

.stat-commits {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.stat-icon svg {
    width: 28px;
    height: 28px;
    stroke: var(--accent);
    flex-shrink: 0;
}

.stat-content {
    flex: 1;
}

.stat-number {
    font-size: 2rem;
    font-weight: 600;
    color: var(--accent);
    letter-spacing: -0.02em;
    line-height: 1;
}

.stat-label {
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin-top: var(--spacing-xs);
}

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

.stat-achievements .stat-label {
    margin-top: 0;
    font-weight: 500;
}

.achievement-badges {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.achievement-badge {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem;
    background: var(--bg-primary);
    border-radius: 6px;
    border: 1px solid var(--border);
}

.achievement-icon svg {
    width: 16px;
    height: 16px;
    stroke: var(--text-secondary);
    flex-shrink: 0;
}

.achievement-badge span {
    font-size: 0.8125rem;
    color: var(--text-primary);
}

/* ============================================
   EDUCATION SECTION
   ============================================ */
.education {
    background: var(--bg-secondary);
}

.education-content {
    max-width: 800px;
    margin: 0 auto;
}

.education-item {
    background: var(--bg-primary);
    padding: var(--spacing-md);
    border-radius: 8px;
    border: 1px solid var(--border);
}

.education-item h3 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-sm);
    color: var(--accent);
    font-weight: 600;
}

.education-details {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
}

.degree {
    font-size: 1rem;
    color: var(--text-primary);
    font-weight: 400;
}

.education-date {
    color: var(--text-secondary);
    font-size: 0.9375rem;
}

/* ============================================
   SKILLS SECTION
   ============================================ */
.skills {
    background: var(--bg-primary);
}

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

.skill-category {
    background: var(--bg-secondary);
    padding: var(--spacing-md);
    border-radius: 8px;
    border: 1px solid var(--border);
}

.skill-category h3 {
    font-size: 1.125rem;
    margin-bottom: var(--spacing-sm);
    color: var(--accent);
    font-weight: 600;
}

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

.skill-tag {
    background: var(--bg-primary);
    padding: 0.5rem 0.875rem;
    border-radius: 6px;
    font-size: 0.875rem;
    color: var(--text-primary);
    border: 1px solid var(--border);
}

/* ============================================
   EXPERIENCE SECTION
   ============================================ */
.experience {
    background: var(--bg-secondary);
}

.timeline {
    position: relative;
    max-width: 900px;
    margin: 0 auto;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
    width: 1px;
    height: 100%;
    background: var(--border);
}

.timeline-item {
    position: relative;
    margin-bottom: var(--spacing-lg);
    display: flex;
    justify-content: flex-end;
    width: 50%;
}

.timeline-item:nth-child(even) {
    align-self: flex-end;
    justify-content: flex-start;
    left: 50%;
}

.timeline-marker {
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
    width: 12px;
    height: 12px;
    background: var(--accent);
    border-radius: 50%;
    border: 3px solid var(--bg-secondary);
    z-index: 1;
}

.timeline-item:nth-child(even) .timeline-marker {
    left: 0;
}

.timeline-content {
    background: var(--bg-primary);
    padding: var(--spacing-md);
    border-radius: 8px;
    border: 1px solid var(--border);
    width: 90%;
}

.timeline-date {
    color: var(--text-secondary);
    font-weight: 500;
    margin-bottom: var(--spacing-xs);
    font-size: 0.875rem;
}

.timeline-content h3 {
    font-size: 1.25rem;
    margin-bottom: 0.25rem;
    font-weight: 600;
}

.timeline-content h4 {
    color: var(--text-secondary);
    font-weight: 400;
    font-size: 1rem;
    margin-bottom: var(--spacing-sm);
}

.timeline-content p {
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: var(--spacing-sm);
    font-size: 0.9375rem;
}

.achievement-list {
    list-style: none;
    padding-left: 0;
}

.achievement-list li {
    color: var(--text-secondary);
    padding-left: 1.25rem;
    margin-bottom: 0.5rem;
    position: relative;
    font-size: 0.9375rem;
}

.achievement-list li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--accent);
    font-weight: bold;
}

/* ============================================
   CONTACT SECTION
   ============================================ */
.contact {
    background: var(--bg-primary);
}

.contact-content {
    max-width: 700px;
    margin: 0 auto;
}

.contact-intro {
    font-size: 1.0625rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    line-height: 1.8;
}

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

.contact-method {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md);
    background: var(--bg-secondary);
    border-radius: 8px;
    border: 1px solid var(--border);
    text-decoration: none;
    color: var(--text-primary);
    transition: all 0.2s ease;
}

.contact-method:hover {
    border-color: var(--accent);
}

.contact-icon svg {
    width: 20px;
    height: 20px;
    stroke: var(--text-primary);
}

/* ============================================
   FOOTER
   ============================================ */
.footer {
    background: var(--bg-secondary);
    padding: var(--spacing-md) 0;
    text-align: center;
    color: var(--text-secondary);
    border-top: 1px solid var(--border);
}

.footer p {
    margin-bottom: 0.5rem;
    font-size: 0.875rem;
}

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

/* ============================================
   RESPONSIVE DESIGN
   ============================================ */
@media (max-width: 968px) {
    .timeline::before {
        left: 0;
    }

    .timeline-item {
        width: 100%;
        padding-left: 40px;
    }

    .timeline-item:nth-child(even) {
        left: 0;
    }

    .timeline-marker {
        left: 0 !important;
    }

    .timeline-content {
        width: 100%;
    }

    .about-content {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    html {
        font-size: 15px;
    }

    .hero-title {
        font-size: 2.25rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .section-title {
        font-size: 1.75rem;
    }

    .nav-links {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        width: 100%;
        background: var(--bg-primary);
        flex-direction: column;
        padding: var(--spacing-sm);
        border-bottom: 1px solid var(--border);
    }

    .nav-links.active {
        display: flex;
    }

    .mobile-menu-toggle {
        display: flex;
    }

    .container {
        padding: 0 var(--spacing-sm);
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 1.875rem;
    }

    .hero-cta {
        flex-direction: column;
    }

    .btn {
        width: 100%;
        text-align: center;
    }
}