/* ===== CSS Variables ===== */
:root {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-card: rgba(30, 41, 59, 0.7);
    --bg-card-hover: rgba(30, 41, 59, 0.9);
    --accent: #2563eb;
    --accent-light: #3b82f6;
    --accent-glow: rgba(37, 99, 235, 0.3);
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --border: rgba(148, 163, 184, 0.1);
    --border-accent: rgba(37, 99, 235, 0.3);
    --glass-bg: rgba(15, 23, 42, 0.6);
    --glass-border: rgba(148, 163, 184, 0.08);
    --shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
    --radius: 12px;
    --radius-sm: 8px;
    --nav-height: 64px;
    --max-width: 1100px;
    --transition: 0.3s ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    -webkit-font-smoothing: antialiased;
}

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

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

/* ===== Navigation ===== */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--nav-height);
    background: rgba(15, 23, 42, 0.85);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--glass-border);
    z-index: 1000;
    transition: background var(--transition);
}

.nav-container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 24px;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.5px;
}

.nav-logo:hover {
    color: var(--accent-light);
}

.nav-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--text-primary);
    font-size: 1.25rem;
    cursor: pointer;
    padding: 8px;
}

.nav-tabs {
    display: flex;
    list-style: none;
    gap: 4px;
}

.tab-link {
    display: block;
    padding: 8px 16px;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    border-radius: var(--radius-sm);
    transition: all var(--transition);
    position: relative;
}

.tab-link:hover {
    color: var(--text-primary);
    background: rgba(148, 163, 184, 0.08);
}

.tab-link.active {
    color: var(--accent-light);
    background: var(--accent-glow);
}

.tab-link.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 20px;
    height: 2px;
    background: var(--accent);
    border-radius: 1px;
}

/* ===== Main Content ===== */
.main {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: calc(var(--nav-height) + 32px) 24px 48px;
}

.section {
    display: none;
    animation: fadeIn 0.4s ease;
}

.section.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(12px); }
    to { opacity: 1; transform: translateY(0); }
}

.section-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 8px;
    letter-spacing: -0.5px;
}

.section-subtitle {
    color: var(--text-secondary);
    margin-bottom: 32px;
    font-size: 1rem;
}

.cert-count {
    color: var(--accent-light);
    font-weight: 700;
}

/* ===== Glass Card ===== */
.glass-card {
    background: var(--bg-card);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius);
    padding: 24px;
    transition: all var(--transition);
}

.glass-card:hover {
    background: var(--bg-card-hover);
    border-color: var(--border-accent);
    box-shadow: 0 8px 32px rgba(37, 99, 235, 0.08);
}

/* ===== Hero / About Me ===== */
.hero {
    display: flex;
    align-items: center;
    gap: 48px;
    margin-bottom: 32px;
    padding: 48px 0;
}

.hero-photo {
    flex-shrink: 0;
}

.profile-photo {
    width: 200px;
    height: 200px;
    border-radius: 50%;
    object-fit: cover;
    border: 3px solid var(--accent);
    box-shadow: 0 0 40px var(--accent-glow), 0 0 80px rgba(37, 99, 235, 0.1);
}

.hero-text {
    flex: 1;
}

.hero-name {
    font-size: 2.5rem;
    font-weight: 700;
    letter-spacing: -1px;
    line-height: 1.1;
    margin-bottom: 8px;
}

.hero-title {
    font-size: 1.15rem;
    color: var(--accent-light);
    font-weight: 500;
    margin-bottom: 20px;
}

.hero-contact {
    display: flex;
    gap: 16px;
}

.hero-contact a {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: var(--bg-card);
    border: 1px solid var(--glass-border);
    color: var(--text-secondary);
    font-size: 1.15rem;
    transition: all var(--transition);
}

.hero-contact a:hover {
    color: var(--accent-light);
    border-color: var(--accent);
    background: var(--accent-glow);
    transform: translateY(-2px);
}

.about-bio {
    max-width: 800px;
}

.about-bio p {
    margin-bottom: 16px;
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.75;
}

.about-bio p:last-child {
    margin-bottom: 0;
}

/* ===== Timeline (Experience & Education) ===== */
.timeline {
    position: relative;
    padding-left: 32px;
    margin-top: 32px;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 7px;
    top: 0;
    bottom: 0;
    width: 2px;
    background: linear-gradient(to bottom, var(--accent), var(--border));
}

.timeline-item {
    position: relative;
    margin-bottom: 32px;
}

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

.timeline-dot {
    position: absolute;
    left: -32px;
    top: 28px;
    width: 16px;
    height: 16px;
    border-radius: 50%;
    background: var(--accent);
    border: 3px solid var(--bg-primary);
    box-shadow: 0 0 12px var(--accent-glow);
    z-index: 1;
}

.timeline-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 16px;
    margin-bottom: 12px;
    flex-wrap: wrap;
}

.timeline-role {
    font-size: 1.15rem;
    font-weight: 600;
    color: var(--text-primary);
}

.timeline-company {
    font-size: 0.95rem;
    color: var(--accent-light);
    font-weight: 500;
    margin-top: 2px;
}

.timeline-date {
    font-size: 0.8rem;
    color: var(--text-muted);
    white-space: nowrap;
    padding: 4px 12px;
    background: rgba(37, 99, 235, 0.1);
    border-radius: 20px;
    font-weight: 500;
    flex-shrink: 0;
}

.timeline-details {
    list-style: none;
    padding: 0;
}

.timeline-details li {
    position: relative;
    padding-left: 20px;
    margin-bottom: 8px;
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.6;
}

.timeline-details li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 10px;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--accent);
}

.metric {
    color: var(--accent-light);
    font-weight: 700;
    background: rgba(37, 99, 235, 0.1);
    padding: 1px 6px;
    border-radius: 4px;
}

/* ===== Education Specific ===== */
.education-stats {
    display: flex;
    gap: 8px;
    margin-bottom: 12px;
    flex-wrap: wrap;
}

.stat-badge {
    font-size: 0.8rem;
    font-weight: 600;
    padding: 4px 12px;
    border-radius: 20px;
    background: rgba(37, 99, 235, 0.15);
    color: var(--accent-light);
    border: 1px solid rgba(37, 99, 235, 0.2);
}

.education-details {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 8px;
}

.education-details:last-child {
    margin-bottom: 0;
}

.dual-degree-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--accent-light);
    margin-bottom: 12px;
}

.dual-degree-badge i {
    color: #fbbf24;
}

.admission-highlight {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 20px;
    padding: 12px 16px;
    background: rgba(37, 99, 235, 0.08);
    border-radius: var(--radius-sm);
    border-left: 3px solid var(--accent);
}

.admission-highlight i {
    color: #fbbf24;
}

.dual-degree-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
}

.dual-degree-card {
    padding: 16px;
    background: rgba(15, 23, 42, 0.4);
    border-radius: var(--radius-sm);
    border: 1px solid var(--glass-border);
}

/* ===== Articles Grid ===== */
.articles-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 20px;
    margin-top: 32px;
}

.article-card {
    display: flex;
    flex-direction: column;
    color: var(--text-primary);
    cursor: pointer;
}

.article-card:hover {
    transform: translateY(-4px);
}

.article-date {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-bottom: 8px;
    display: flex;
    align-items: center;
    gap: 6px;
}

.article-date i {
    color: var(--text-muted);
}

.article-title {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 8px;
    line-height: 1.4;
    color: var(--text-primary);
}

.article-desc {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.6;
    flex: 1;
}

/* ===== Certifications ===== */
.cert-filters {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
    flex-wrap: wrap;
}

.cert-filter {
    padding: 6px 16px;
    font-size: 0.8rem;
    font-weight: 500;
    border: 1px solid var(--glass-border);
    border-radius: 20px;
    background: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition);
    font-family: inherit;
}

.cert-filter:hover {
    border-color: var(--accent);
    color: var(--text-primary);
}

.cert-filter.active {
    background: var(--accent);
    border-color: var(--accent);
    color: white;
}

.certs-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 16px;
}

.cert-card {
    padding: 20px;
    transition: all var(--transition);
}

.cert-card.hidden {
    display: none;
}

.cert-institution {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 8px;
    display: flex;
    align-items: center;
    gap: 6px;
}

.cert-name {
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: 4px;
    line-height: 1.4;
}


.cert-desc {
    font-size: 0.82rem;
    color: var(--text-secondary);
    line-height: 1.5;
    margin-bottom: 12px;
}

.cert-verify {
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--accent-light);
    display: inline-flex;
    align-items: center;
    gap: 4px;
}

.cert-verify:hover {
    color: var(--text-primary);
}

/* ===== Skills ===== */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
    gap: 20px;
    margin-top: 32px;
}

.skill-category {
    padding: 24px;
}

.skill-category-title {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 16px;
    display: flex;
    align-items: center;
    gap: 8px;
    color: var(--text-primary);
}

.skill-category-title i {
    color: var(--accent-light);
    font-size: 0.9rem;
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.skill-tag {
    font-size: 0.8rem;
    font-weight: 500;
    padding: 5px 12px;
    border-radius: 20px;
    background: rgba(37, 99, 235, 0.1);
    border: 1px solid rgba(37, 99, 235, 0.15);
    color: var(--text-secondary);
    transition: all var(--transition);
}

.skill-tag:hover {
    background: rgba(37, 99, 235, 0.2);
    color: var(--text-primary);
    border-color: rgba(37, 99, 235, 0.3);
}

.languages {
    margin-top: 16px;
    padding-top: 16px;
    border-top: 1px solid var(--glass-border);
}

.languages-title {
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 10px;
    color: var(--text-muted);
}

.lang-tag small {
    color: var(--text-muted);
    font-weight: 400;
}

/* ===== Footer ===== */
.footer {
    border-top: 1px solid var(--glass-border);
    padding: 32px 24px;
    margin-top: 64px;
}

.footer-content {
    max-width: var(--max-width);
    margin: 0 auto;
    text-align: center;
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: 24px;
    margin-bottom: 16px;
    flex-wrap: wrap;
}

.footer-links a {
    font-size: 0.85rem;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    gap: 6px;
    transition: color var(--transition);
}

.footer-links a:hover {
    color: var(--accent-light);
}

.footer-copy {
    font-size: 0.8rem;
    color: var(--text-muted);
}

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

    .nav-tabs {
        display: none;
        position: absolute;
        top: var(--nav-height);
        left: 0;
        right: 0;
        background: rgba(15, 23, 42, 0.95);
        backdrop-filter: blur(16px);
        -webkit-backdrop-filter: blur(16px);
        flex-direction: column;
        padding: 12px;
        border-bottom: 1px solid var(--glass-border);
    }

    .nav-tabs.open {
        display: flex;
    }

    .tab-link {
        padding: 12px 16px;
    }

    .hero {
        flex-direction: column;
        text-align: center;
        gap: 24px;
        padding: 32px 0;
    }

    .hero-name {
        font-size: 1.75rem;
    }

    .hero-contact {
        justify-content: center;
    }

    .profile-photo {
        width: 150px;
        height: 150px;
    }

    .dual-degree-grid {
        grid-template-columns: 1fr;
    }

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

    .timeline-header {
        flex-direction: column;
        gap: 8px;
    }

    .section-title {
        font-size: 1.5rem;
    }

    .footer-links {
        flex-direction: column;
        align-items: center;
        gap: 12px;
    }
}

@media (max-width: 480px) {
    .main {
        padding: calc(var(--nav-height) + 16px) 16px 32px;
    }

    .glass-card {
        padding: 16px;
    }

    .hero-name {
        font-size: 1.5rem;
    }

    .education-stats {
        flex-direction: column;
        align-items: flex-start;
    }
}