/* ============================================
   CSS Custom Properties
   ============================================ */
:root {
    /* Colors */
    --color-bg: #0f1117;
    --color-bg-alt: #161822;
    --color-surface: #1c1e2e;
    --color-surface-hover: #242640;
    --color-border: #2a2d42;
    --color-text: #e2e4f0;
    --color-text-muted: #8b8fa8;
    --color-text-dim: #5c6080;
    --color-primary: #6366f1;
    --color-primary-light: #818cf8;
    --color-accent: #06b6d4;
    --color-gradient-start: #6366f1;
    --color-gradient-end: #06b6d4;

    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 4rem;
    --space-4xl: 6rem;

    /* Borders */
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 400ms ease;

    /* Layout */
    --max-width: 1100px;
    --nav-height: 64px;
}

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

html {
    scroll-behavior: smooth;
    scroll-padding-top: var(--nav-height);
}

body {
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-text);
    background-color: var(--color-bg);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

a:hover {
    color: var(--color-accent);
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    display: block;
}

/* ============================================
   Utility
   ============================================ */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--space-xl);
}

/* ============================================
   Navigation
   ============================================ */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--nav-height);
    background: rgba(15, 17, 23, 0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid transparent;
    z-index: 1000;
    transition: border-color var(--transition-base);
}

.nav.scrolled {
    border-bottom-color: var(--color-border);
}

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

.nav-logo {
    font-family: var(--font-mono);
    font-size: 1.25rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.nav-logo:hover {
    opacity: 0.8;
}

.nav-menu {
    display: flex;
    gap: var(--space-lg);
}

.nav-link {
    color: var(--color-text-muted);
    font-size: 0.9rem;
    font-weight: 500;
    padding: var(--space-xs) 0;
    position: relative;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 0;
    height: 2px;
    background: linear-gradient(90deg, var(--color-gradient-start), var(--color-gradient-end));
    transition: width var(--transition-base);
}

.nav-link:hover,
.nav-link.active {
    color: var(--color-text);
}

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

/* Mobile nav toggle */
.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-sm);
}

.nav-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-text);
    transition: var(--transition-fast);
}

/* ============================================
   Hero
   ============================================ */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: var(--space-4xl) var(--space-xl);
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(ellipse at 30% 50%, rgba(99, 102, 241, 0.12) 0%, transparent 60%),
                radial-gradient(ellipse at 70% 50%, rgba(6, 182, 212, 0.08) 0%, transparent 60%);
    animation: heroGlow 8s ease-in-out infinite alternate;
}

@keyframes heroGlow {
    0% { transform: translate(0, 0); }
    100% { transform: translate(-2%, 2%); }
}

.hero-content {
    position: relative;
    z-index: 1;
}

.hero-greeting {
    font-family: var(--font-mono);
    font-size: 1rem;
    color: var(--color-accent);
    margin-bottom: var(--space-sm);
}

.hero-title {
    font-size: clamp(2.5rem, 6vw, 4.5rem);
    font-weight: 700;
    line-height: 1.1;
    margin-bottom: var(--space-md);
    background: linear-gradient(135deg, var(--color-text) 0%, var(--color-text-muted) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: clamp(1.25rem, 3vw, 1.75rem);
    font-weight: 600;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--space-lg);
}

.hero-description {
    font-size: 1.1rem;
    color: var(--color-text-muted);
    max-width: 540px;
    margin: 0 auto var(--space-2xl);
    line-height: 1.7;
}

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

/* ============================================
   Buttons
   ============================================ */
.btn {
    display: inline-block;
    padding: 0.75rem 1.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-base);
    border: 1px solid transparent;
}

.btn-primary {
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    color: #fff;
}

.btn-primary:hover {
    opacity: 0.9;
    transform: translateY(-1px);
    color: #fff;
}

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

.btn-outline:hover {
    border-color: var(--color-primary);
    color: var(--color-primary-light);
    background: rgba(99, 102, 241, 0.05);
}

/* ============================================
   Sections
   ============================================ */
.section {
    padding: var(--space-4xl) 0;
}

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

.section-title {
    font-size: 2rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: var(--space-3xl);
    position: relative;
}

.section-title::after {
    content: '';
    display: block;
    width: 60px;
    height: 3px;
    background: linear-gradient(90deg, var(--color-gradient-start), var(--color-gradient-end));
    margin: var(--space-md) auto 0;
    border-radius: 2px;
}

/* ============================================
   About
   ============================================ */
.about-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-3xl);
    align-items: start;
}

.about-text p {
    color: var(--color-text-muted);
    margin-bottom: var(--space-md);
    line-height: 1.8;
}

.about-stats {
    display: grid;
    gap: var(--space-md);
}

.stat-card {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--space-lg);
    text-align: center;
    transition: border-color var(--transition-base);
}

.stat-card:hover {
    border-color: var(--color-primary);
}

.stat-number {
    display: block;
    font-size: 2rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.stat-label {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    margin-top: var(--space-xs);
}

/* ============================================
   Skills
   ============================================ */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-lg);
}

.skill-card {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--space-xl);
    transition: all var(--transition-base);
}

.skill-card:hover {
    border-color: var(--color-primary);
    box-shadow: 0 0 20px rgba(99, 102, 241, 0.1);
    transform: translateY(-2px);
}

.skill-title {
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: var(--space-md);
    color: var(--color-text);
}

.skill-list li {
    font-size: 0.875rem;
    color: var(--color-text-muted);
    padding: var(--space-xs) 0;
    font-family: var(--font-mono);
}

.skill-list li::before {
    content: '\25B8 ';
    color: var(--color-accent);
}

/* ============================================
   Timeline / Experience
   ============================================ */
.timeline {
    position: relative;
    max-width: 700px;
    margin: 0 auto;
    padding-left: var(--space-2xl);
}

.timeline::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 2px;
    background: linear-gradient(180deg, var(--color-gradient-start), var(--color-gradient-end), transparent);
}

.timeline-item {
    position: relative;
    margin-bottom: var(--space-3xl);
}

.timeline-item:last-child {
    margin-bottom: 0;
}

.timeline-marker {
    position: absolute;
    left: calc(-1 * var(--space-2xl) - 5px);
    top: 6px;
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: var(--color-primary);
    border: 2px solid var(--color-bg);
}

.timeline-content {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--space-xl);
    transition: border-color var(--transition-base);
}

.timeline-content:hover {
    border-color: var(--color-primary);
}

.timeline-title {
    font-size: 1.15rem;
    font-weight: 600;
    margin-bottom: var(--space-xs);
}

.timeline-company {
    color: var(--color-primary-light);
    font-size: 0.95rem;
    margin-bottom: var(--space-xs);
}

.timeline-date {
    font-size: 0.85rem;
    color: var(--color-text-dim);
    font-family: var(--font-mono);
    margin-bottom: var(--space-md);
}

.timeline-details {
    list-style: none;
}

.timeline-details li {
    font-size: 0.9rem;
    color: var(--color-text-muted);
    padding: var(--space-xs) 0;
    padding-left: var(--space-md);
    position: relative;
}

.timeline-details li::before {
    content: '\25B8';
    position: absolute;
    left: 0;
    color: var(--color-accent);
}

/* ============================================
   Projects
   ============================================ */
.projects-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-lg);
}

.project-card {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--space-xl);
    transition: all var(--transition-base);
}

.project-card:hover {
    border-color: var(--color-primary);
    box-shadow: 0 0 24px rgba(99, 102, 241, 0.08);
    transform: translateY(-2px);
}

.project-title {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: var(--space-sm);
}

.project-description {
    font-size: 0.9rem;
    color: var(--color-text-muted);
    line-height: 1.7;
    margin-bottom: var(--space-md);
}

.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-sm);
}

.tag {
    font-size: 0.75rem;
    font-family: var(--font-mono);
    padding: 0.25rem 0.6rem;
    border-radius: var(--radius-sm);
    background: rgba(99, 102, 241, 0.1);
    color: var(--color-primary-light);
    border: 1px solid rgba(99, 102, 241, 0.2);
}

/* ============================================
   Certifications
   ============================================ */
.certs-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-lg);
}

.cert-card {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--space-xl);
    text-align: center;
    transition: all var(--transition-base);
}

.cert-card:hover {
    border-color: var(--color-primary);
    box-shadow: 0 0 20px rgba(99, 102, 241, 0.1);
}

.cert-title {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: var(--space-sm);
}

.cert-issuer {
    font-size: 0.85rem;
    color: var(--color-text-muted);
}

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

.contact-description {
    color: var(--color-text-muted);
    font-size: 1.05rem;
    margin-bottom: var(--space-2xl);
}

.contact-links {
    display: flex;
    justify-content: center;
    gap: var(--space-xl);
    flex-wrap: wrap;
}

.contact-link {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    color: var(--color-text-muted);
    font-size: 0.95rem;
    padding: var(--space-md) var(--space-lg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    transition: all var(--transition-base);
}

.contact-link:hover {
    color: var(--color-text);
    border-color: var(--color-primary);
    background: rgba(99, 102, 241, 0.05);
}

.contact-icon {
    font-size: 1.25rem;
}

/* ============================================
   Footer
   ============================================ */
.footer {
    padding: var(--space-xl) 0;
    text-align: center;
    border-top: 1px solid var(--color-border);
    color: var(--color-text-dim);
    font-size: 0.85rem;
}

/* ============================================
   Section Subtitle
   ============================================ */
.section-subtitle {
    font-size: 1.1rem;
    font-weight: 600;
    margin: 2rem 0 1rem;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* ============================================
   Animations
   ============================================ */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

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

/* ============================================
   Responsive - Tablet (768px)
   ============================================ */
@media (max-width: 768px) {
    .nav-toggle {
        display: flex;
    }

    .nav-menu {
        position: fixed;
        top: var(--nav-height);
        left: 0;
        right: 0;
        background: rgba(15, 17, 23, 0.95);
        backdrop-filter: blur(12px);
        flex-direction: column;
        align-items: center;
        padding: var(--space-xl) 0;
        gap: var(--space-md);
        transform: translateY(-100%);
        opacity: 0;
        pointer-events: none;
        transition: all var(--transition-base);
        border-bottom: 1px solid var(--color-border);
    }

    .nav-menu.open {
        transform: translateY(0);
        opacity: 1;
        pointer-events: all;
    }

    .about-grid {
        grid-template-columns: 1fr;
        gap: var(--space-2xl);
    }

    .about-stats {
        grid-template-columns: repeat(3, 1fr);
    }

    .skills-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .projects-grid {
        grid-template-columns: 1fr;
    }

    .certs-grid {
        grid-template-columns: 1fr;
    }

    .contact-links {
        flex-direction: column;
        align-items: center;
    }
}

/* ============================================
   Responsive - Mobile (480px)
   ============================================ */
@media (max-width: 480px) {
    .container {
        padding: 0 var(--space-md);
    }

    .section {
        padding: var(--space-3xl) 0;
    }

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

    .skills-grid {
        grid-template-columns: 1fr;
    }

    .hero-actions {
        flex-direction: column;
        align-items: center;
    }

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