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

:root {
    --bg: #fafafa;
    --bg-alt: #f0f0f0;
    --text: #1a1a1a;
    --text-secondary: #555;
    --accent: #2563eb;
    --accent-hover: #1d4ed8;
    --border: #e0e0e0;
    --card-bg: #fff;
    --card-shadow: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
    --card-shadow-hover: 0 4px 12px rgba(0,0,0,0.1);
    --radius: 8px;
    --max-width: 1100px;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: 80px;
}

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

a {
    color: var(--accent);
    text-decoration: none;
    transition: color 0.2s;
}
a:hover {
    color: var(--accent-hover);
}

/* ===== Navbar ===== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    background: rgba(250, 250, 250, 0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid transparent;
    transition: border-color 0.3s, background 0.3s;
}
.navbar.scrolled {
    border-bottom-color: var(--border);
    background: rgba(250, 250, 250, 0.95);
}

.nav-content {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
}

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

.nav-links {
    list-style: none;
    display: flex;
    gap: 28px;
}
.nav-links a {
    color: var(--text-secondary);
    font-size: 0.875rem;
    font-weight: 500;
    transition: color 0.2s;
}
.nav-links a:hover {
    color: var(--text);
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
}
.nav-toggle span {
    display: block;
    width: 22px;
    height: 2px;
    background: var(--text);
    border-radius: 2px;
    transition: transform 0.3s, opacity 0.3s;
}
.nav-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
}
.nav-toggle.active span:nth-child(2) {
    opacity: 0;
}
.nav-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
}

/* ===== Hero ===== */
.hero {
    padding: 160px 24px 100px;
    text-align: center;
}

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

.hero h1 {
    font-size: 2.75rem;
    font-weight: 700;
    letter-spacing: -1px;
    margin-bottom: 12px;
    line-height: 1.1;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--accent);
    font-weight: 500;
    margin-bottom: 16px;
}

.hero-tagline {
    font-size: 1.05rem;
    color: var(--text-secondary);
    max-width: 550px;
    margin: 0 auto 32px;
}

.hero-links {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
}

.btn {
    display: inline-block;
    padding: 10px 24px;
    border-radius: 6px;
    font-size: 0.9rem;
    font-weight: 500;
    transition: all 0.2s;
}
.btn-primary {
    background: var(--accent);
    color: #fff;
}
.btn-primary:hover {
    background: var(--accent-hover);
    color: #fff;
}
.btn-secondary {
    background: var(--card-bg);
    color: var(--text);
    border: 1px solid var(--border);
}
.btn-secondary:hover {
    border-color: var(--accent);
    color: var(--accent);
}

/* ===== Sections ===== */
.section {
    padding: 80px 24px;
}
.section-alt {
    background: var(--bg-alt);
}

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

.section-title {
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: 40px;
    letter-spacing: -0.5px;
}

/* ===== Timeline ===== */
.timeline {
    position: relative;
    padding-left: 32px;
}
.timeline::before {
    content: '';
    position: absolute;
    left: 7px;
    top: 8px;
    bottom: 8px;
    width: 2px;
    background: var(--border);
}

.timeline-item {
    position: relative;
    margin-bottom: 48px;
}
.timeline-item:last-child {
    margin-bottom: 0;
}

.timeline-marker {
    position: absolute;
    left: -32px;
    top: 6px;
    width: 16px;
    height: 16px;
    border-radius: 50%;
    background: var(--card-bg);
    border: 3px solid var(--accent);
    z-index: 1;
}

.timeline-header h3 {
    font-size: 1.25rem;
    font-weight: 600;
}
.timeline-role {
    display: inline-block;
    font-size: 0.9rem;
    color: var(--accent);
    font-weight: 500;
}
.timeline-date {
    display: inline-block;
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-left: 8px;
}

.timeline-body {
    margin-top: 12px;
}
.timeline-body ul {
    padding-left: 20px;
}
.timeline-body li {
    margin-bottom: 8px;
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.experience-block {
    margin-bottom: 20px;
}
.experience-block h4 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 6px;
}
.date-tag {
    font-size: 0.8rem;
    font-weight: 400;
    color: var(--text-secondary);
}
.experience-block p {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.highlight {
    margin-top: 16px;
    padding: 12px 16px;
    background: rgba(37, 99, 235, 0.06);
    border-left: 3px solid var(--accent);
    border-radius: 0 var(--radius) var(--radius) 0;
    font-size: 0.9rem;
    color: var(--accent);
    font-weight: 500;
}

/* ===== Project Grid ===== */
.project-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

.project-card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 24px;
    transition: box-shadow 0.2s, transform 0.2s;
}
.project-card:hover {
    box-shadow: var(--card-shadow-hover);
    transform: translateY(-2px);
}

.project-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 10px;
}
.project-header h3 {
    font-size: 1.05rem;
    font-weight: 600;
}
.stars {
    font-size: 0.8rem;
    color: var(--text-secondary);
    white-space: nowrap;
}

.project-card > p {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 14px;
}

.tags {
    display: flex;
    gap: 6px;
    flex-wrap: wrap;
}
.tag {
    display: inline-block;
    padding: 3px 10px;
    background: var(--bg-alt);
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-secondary);
}

/* ===== Publications ===== */
.publication-card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 28px;
}
.publication-card h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 10px;
}
.publication-card p {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

/* ===== Speaking ===== */
.speaking-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

.speaking-card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 24px;
}
.speaking-type {
    display: inline-block;
    padding: 3px 10px;
    background: var(--accent);
    color: #fff;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 12px;
}
.speaking-card h3 {
    font-size: 1.05rem;
    font-weight: 600;
    margin-bottom: 8px;
}
.talk-title {
    font-style: italic;
    color: var(--accent);
    margin-bottom: 8px;
    font-size: 0.9rem;
}
.speaking-card p {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* ===== Education ===== */
.education-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

.education-card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 24px;
}
.education-card h3 {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 6px;
}
.degree {
    color: var(--accent);
    font-weight: 500;
    font-size: 0.95rem;
}
.specialization {
    color: var(--text-secondary);
    font-size: 0.9rem;
}
.edu-date {
    color: var(--text-secondary);
    font-size: 0.85rem;
    margin-top: 8px;
}

/* ===== Skills ===== */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 24px;
}

.skill-category h3 {
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: 10px;
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}
.skill-tags span {
    display: inline-block;
    padding: 6px 14px;
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 20px;
    font-size: 0.85rem;
    color: var(--text-secondary);
    transition: border-color 0.2s, color 0.2s;
}
.skill-tags span:hover {
    border-color: var(--accent);
    color: var(--accent);
}

/* ===== Memberships ===== */
.membership-list {
    display: flex;
    gap: 20px;
    flex-wrap: wrap;
}

.membership-item {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 20px 28px;
    display: flex;
    flex-direction: column;
    gap: 4px;
}
.membership-org {
    font-size: 1.1rem;
    font-weight: 600;
}
.membership-level {
    font-size: 0.85rem;
    color: var(--text-secondary);
}

/* ===== Contact ===== */
.contact-grid {
    display: flex;
    gap: 20px;
    flex-wrap: wrap;
}

.contact-item {
    display: flex;
    flex-direction: column;
    gap: 4px;
    padding: 20px 28px;
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    transition: border-color 0.2s;
    min-width: 200px;
}
.contact-item:hover {
    border-color: var(--accent);
}
.contact-label {
    font-size: 0.8rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-secondary);
}
.contact-value {
    font-size: 0.95rem;
    color: var(--text);
}

/* ===== Footer ===== */
.footer {
    text-align: center;
    padding: 32px 24px;
    border-top: 1px solid var(--border);
    font-size: 0.85rem;
    color: var(--text-secondary);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .nav-toggle {
        display: flex;
    }
    .nav-links {
        display: none;
        position: absolute;
        top: 64px;
        left: 0;
        right: 0;
        background: rgba(250, 250, 250, 0.98);
        backdrop-filter: blur(12px);
        flex-direction: column;
        padding: 16px 24px;
        gap: 12px;
        border-bottom: 1px solid var(--border);
    }
    .nav-links.active {
        display: flex;
    }

    .hero {
        padding: 130px 20px 70px;
    }
    .hero h1 {
        font-size: 2rem;
    }
    .hero-subtitle {
        font-size: 1.1rem;
    }

    .section {
        padding: 60px 20px;
    }
    .section-title {
        font-size: 1.5rem;
        margin-bottom: 28px;
    }

    .project-grid,
    .speaking-grid,
    .education-grid,
    .skills-grid {
        grid-template-columns: 1fr;
    }

    .contact-grid,
    .membership-list {
        flex-direction: column;
    }
}