/* ===== CSS Variables & Reset ===== */
:root {
    --color-primary: #0f2b46;
    --color-primary-light: #1a4a73;
    --color-accent: #2563eb;
    --color-accent-soft: #eff6ff;
    --color-accent-hover: #1d4ed8;
    --color-text: #0f172a;
    --color-text-secondary: #475569;
    --color-text-muted: #64748b;
    --color-bg: #ffffff;
    --color-bg-alt: #f8fafc;
    --color-border: #e2e8f0;
    --color-border-light: #f1f5f9;
    --color-wp: #b45309;
    --color-wp-bg: #fffbeb;
    --color-ur: #1d4ed8;
    --color-ur-bg: #eff6ff;
    --color-rr: #b91c1c;
    --color-rr-bg: #fef2f2;
    --color-highlight: #7c3aed;
    --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-heading: 'Playfair Display', Georgia, 'Times New Roman', serif;
    --font-serif: 'Source Serif 4', Georgia, serif;
    --max-width: 980px;
    --radius: 10px;
    --radius-lg: 16px;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
    --shadow-md: 0 4px 16px rgba(0,0,0,0.08);
    --shadow-lg: 0 8px 30px rgba(0,0,0,0.1);
    --transition: 0.25s ease;

    /* Spacing (tune these to tighten/loosen the whole page) */
    --space-section: 56px;
    --space-title: 24px;
    --space-card: 24px;
    --space-item: 22px;
}

*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: 72px;
}

body {
    font-family: var(--font-body);
    color: var(--color-text);
    background: var(--color-bg);
    line-height: 1.75;
    -webkit-font-smoothing: antialiased;
}

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

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

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

::selection {
    background: var(--color-accent);
    color: #fff;
}

/* ===== Navigation ===== */
#navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    background: rgba(255,255,255,0.88);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid transparent;
    transition: all var(--transition);
}

#navbar.scrolled {
    border-bottom-color: var(--color-border);
    box-shadow: 0 1px 8px rgba(0,0,0,0.04);
}

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

.nav-brand {
    font-family: var(--font-heading);
    font-weight: 700;
    font-size: 1.2rem;
    color: var(--color-primary);
    letter-spacing: -0.01em;
}

.nav-links {
    display: flex;
    gap: 32px;
}

.nav-links a {
    font-size: 0.85rem;
    font-weight: 500;
    color: var(--color-text-secondary);
    transition: color var(--transition);
    position: relative;
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--color-accent);
    transition: width var(--transition);
}

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

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

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
}

.nav-toggle span {
    width: 22px;
    height: 2px;
    background: var(--color-text);
    border-radius: 2px;
    transition: all var(--transition);
}

/* ===== Hero ===== */
#hero {
    position: relative;
    padding: 140px 24px 80px;
    background: linear-gradient(135deg, #0f2b46 0%, #1a4a73 40%, #2563eb 100%);
    color: #fff;
    overflow: hidden;
}

.hero-bg-shapes {
    position: absolute;
    inset: 0;
    pointer-events: none;
    overflow: hidden;
}

.shape {
    position: absolute;
    border-radius: 50%;
    opacity: 0.08;
    background: #fff;
}

.shape-1 {
    width: 600px;
    height: 600px;
    top: -200px;
    right: -100px;
}

.shape-2 {
    width: 400px;
    height: 400px;
    bottom: -150px;
    left: -100px;
}

.shape-3 {
    width: 200px;
    height: 200px;
    top: 50%;
    left: 60%;
}

.hero-container {
    max-width: var(--max-width);
    margin: 0 auto;
    display: flex;
    align-items: center;
    gap: 56px;
    position: relative;
    z-index: 1;
}

.hero-image-wrapper {
    flex-shrink: 0;
    position: relative;
}

.hero-image-ring {
    position: absolute;
    inset: -8px;
    border-radius: 50%;
    border: 2px solid rgba(255,255,255,0.3);
}

.hero-image {
    max-width: 450px;
    height: auto;
    border-radius: 12px;
    object-fit: cover;
    border: 4px solid rgba(255,255,255,0.5);
    box-shadow: 0 8px 32px rgba(0,0,0,0.3);
}

.hero-text h1 {
    font-family: var(--font-heading);
    font-size: 3.2rem;
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: 12px;
    letter-spacing: -0.02em;
}

.hero-greeting {
    font-size: 1rem;
    font-weight: 400;
    opacity: 0.8;
    margin-bottom: 4px;
    letter-spacing: 0.05em;
    text-transform: uppercase;
}

.hero-subtitle {
    font-size: 1.2rem;
    font-weight: 500;
    margin-bottom: 6px;
    opacity: 0.95;
}

.hero-affiliation {
    font-size: 0.92rem;
    opacity: 0.8;
    line-height: 1.6;
    display: flex;
    align-items: center;
    gap: 6px;
}

.hero-affiliation svg {
    flex-shrink: 0;
    opacity: 0.7;
}

.hero-contact-row {
    margin-top: 20px;
    display: flex;
    gap: 12px;
}

.contact-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 18px;
    font-size: 0.85rem;
    font-weight: 500;
    border-radius: 8px;
    background: rgba(255,255,255,0.15);
    color: #fff;
    border: 1px solid rgba(255,255,255,0.25);
    transition: all var(--transition);
    backdrop-filter: blur(4px);
}

.contact-btn:hover {
    background: rgba(255,255,255,0.25);
    color: #fff;
    transform: translateY(-1px);
}

.hero-tags {
    margin-top: 22px;
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.hero-tags .tag {
    display: inline-block;
    padding: 5px 14px;
    font-size: 0.78rem;
    font-weight: 500;
    background: rgba(255,255,255,0.12);
    color: rgba(255,255,255,0.9);
    border-radius: 20px;
    border: 1px solid rgba(255,255,255,0.2);
    backdrop-filter: blur(4px);
}

.hero-scroll-hint {
    position: relative;
    z-index: 1;
    margin-top: 48px;
    text-align: center;
}

.hero-scroll-hint a {
    display: inline-flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
    color: rgba(255,255,255,0.5);
    font-size: 0.75rem;
    font-weight: 500;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    transition: color var(--transition);
    animation: bounce 2s ease infinite;
}

.hero-scroll-hint a:hover {
    color: rgba(255,255,255,0.8);
}

@keyframes bounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(6px); }
}

/* ===== Sections ===== */
.section {
    padding: var(--space-section) 24px;
}

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

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

.section-title {
    font-family: var(--font-heading);
    font-size: 2rem;
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: 12px;
    letter-spacing: -0.01em;
}

.section-title::after {
    content: '';
    display: block;
    width: 48px;
    height: 3px;
    background: var(--color-accent);
    border-radius: 2px;
    margin-top: 12px;
    margin-bottom: var(--space-title);
}

.section-subtitle {
    font-size: 0.95rem;
    color: var(--color-text-muted);
    margin-top: -24px;
    margin-bottom: 32px;
    font-weight: 500;
}

.research-subhead {
    font-family: var(--font-heading);
    font-size: 1.35rem;
    font-weight: 700;
    color: var(--color-text);
    margin: 32px 0 20px;
    padding-top: 16px;
    border-top: 1px solid var(--color-border-light);
}

/* ===== About ===== */
.about-grid {
    display: grid;
    /* Sidebar highlights are hidden; single column. Restore to
       'grid-template-columns: 1.6fr 1fr' when uncommenting .about-sidebar */
    grid-template-columns: 1fr;
    gap: 40px;
    align-items: start;
}

.about-main p {
    font-family: var(--font-serif);
    font-size: 1.02rem;
    color: var(--color-text-secondary);
    line-height: 1.8;
    margin-bottom: 16px;
}

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

.about-sidebar {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.about-highlight {
    display: flex;
    gap: 14px;
    padding: 20px;
    background: var(--color-bg-alt);
    border-radius: var(--radius);
    border: 1px solid var(--color-border-light);
    transition: all var(--transition);
}

.about-highlight:hover {
    border-color: var(--color-accent);
    box-shadow: var(--shadow-sm);
    transform: translateY(-1px);
}

.highlight-icon {
    flex-shrink: 0;
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-accent-soft);
    color: var(--color-accent);
    border-radius: 10px;
}

.about-highlight h4 {
    font-size: 0.92rem;
    font-weight: 600;
    color: var(--color-text);
    margin-bottom: 2px;
}

.about-highlight p {
    font-size: 0.82rem;
    color: var(--color-text-muted);
    line-height: 1.5;
}

/* ===== Research Interests ===== */
.interests-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 28px;
}

.interest-card {
    background: #fff;
    padding: var(--space-card);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition);
}

.interest-card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-3px);
    border-color: var(--color-accent);
}

.interest-icon {
    color: var(--color-accent);
    margin-bottom: 14px;
}

.interest-card h3 {
    font-family: var(--font-heading);
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: 4px;
}

.interest-desc {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    margin-bottom: 16px;
}

.interest-items {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.pill {
    display: inline-block;
    padding: 6px 14px;
    font-size: 0.82rem;
    background: var(--color-accent-soft);
    color: var(--color-accent);
    border-radius: 8px;
    font-weight: 500;
    transition: all var(--transition);
}

.pill:hover {
    background: var(--color-accent);
    color: #fff;
}

/* ===== Education Timeline ===== */
.timeline {
    position: relative;
    padding-left: 36px;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 8px;
    top: 12px;
    bottom: 12px;
    width: 2px;
    background: linear-gradient(to bottom, var(--color-accent), var(--color-border));
    border-radius: 2px;
}

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

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

.timeline-marker {
    position: absolute;
    left: -36px;
    top: 8px;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: #fff;
    border: 3px solid var(--color-accent);
    box-shadow: 0 0 0 4px var(--color-accent-soft);
}

.timeline-item:first-child .timeline-marker {
    background: var(--color-accent);
}

.timeline-content {
    background: #fff;
    padding: var(--space-card);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition);
}

.timeline-content:hover {
    box-shadow: var(--shadow-md);
    border-color: rgba(37, 99, 235, 0.2);
}

.timeline-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 16px;
    margin-bottom: 10px;
}

.timeline-header h3 {
    font-family: var(--font-heading);
    font-size: 1.15rem;
    font-weight: 700;
    color: var(--color-primary);
}

.degree {
    font-size: 0.95rem;
    color: var(--color-text);
    font-weight: 500;
    font-family: var(--font-serif);
}

.timeline-meta {
    text-align: right;
    flex-shrink: 0;
}

.timeline-date {
    display: block;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--color-accent);
    white-space: nowrap;
}

.timeline-location {
    display: block;
    font-size: 0.82rem;
    color: var(--color-text-muted);
    white-space: nowrap;
}

.edu-detail {
    font-size: 0.88rem;
    color: var(--color-text-secondary);
    margin-bottom: 6px;
}

.edu-courses {
    font-size: 0.84rem;
    color: var(--color-text-muted);
    line-height: 1.65;
}

/* ===== Research Papers ===== */
.papers-list {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.paper-item {
    position: relative;
    background: #fff;
    padding: var(--space-card);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition);
    overflow: hidden;
}

.paper-item:hover {
    box-shadow: var(--shadow-md);
    border-color: rgba(37, 99, 235, 0.2);
}

.paper-item.featured-paper {
    border-left: 4px solid var(--color-accent);
}

.paper-badge {
    position: absolute;
    top: 0;
    right: 28px;
    padding: 4px 14px;
    font-size: 0.72rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: #fff;
    background: var(--color-accent);
    border-radius: 0 0 8px 8px;
}

.paper-content {
    /* no flex needed — full width now */
}

.paper-authors {
    font-size: 0.9rem;
    color: var(--color-text-secondary);
    margin-bottom: 6px;
    line-height: 1.5;
}

.paper-title {
    font-family: var(--font-heading);
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--color-text);
    margin-bottom: 10px;
    line-height: 1.4;
}

.paper-meta {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 16px;
}

.paper-status {
    display: inline-block;
    padding: 4px 12px;
    font-size: 0.75rem;
    font-weight: 600;
    border-radius: 6px;
}

.status-wp {
    background: var(--color-wp-bg);
    color: var(--color-wp);
    border: 1px solid rgba(180, 83, 9, 0.15);
}

.status-ur {
    background: var(--color-ur-bg);
    color: var(--color-ur);
    border: 1px solid rgba(29, 78, 216, 0.15);
}

.status-rr {
    background: var(--color-ur-bg);
    color: var(--color-ur);
    border: 1px solid rgba(29, 78, 216, 0.15);
}

.paper-journal {
    font-size: 0.85rem;
    font-style: italic;
    color: var(--color-text-secondary);
    font-weight: 500;
}

.paper-year {
    font-size: 0.82rem;
    color: var(--color-text-muted);
    font-weight: 600;
}

.paper-link {
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--color-accent);
    text-decoration: none;
    border: 1px solid rgba(37, 99, 235, 0.25);
    border-radius: 6px;
    padding: 2px 8px;
    transition: all var(--transition);
}

.paper-link:hover {
    background: rgba(37, 99, 235, 0.08);
    border-color: var(--color-accent);
}

/* Abstract toggle */
.paper-abstract-toggle {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 6px 16px;
    font-size: 0.82rem;
    font-weight: 600;
    color: var(--color-accent);
    background: var(--color-accent-soft);
    border: 1px solid rgba(37, 99, 235, 0.15);
    border-radius: 8px;
    cursor: pointer;
    transition: all var(--transition);
    user-select: none;
}

.paper-abstract-toggle:hover {
    background: rgba(37, 99, 235, 0.12);
    border-color: var(--color-accent);
}

.toggle-arrow {
    transition: transform var(--transition);
}

.paper-abstract-toggle.open .toggle-arrow {
    transform: rotate(180deg);
}

.paper-abstract {
    display: none;
    margin-top: 16px;
}

.paper-abstract.open {
    max-height: 800px;
    margin-top: 16px;
    opacity: 1;
}

.paper-abstract p {
    font-family: var(--font-serif);
    font-size: 0.92rem;
    color: var(--color-text-secondary);
    line-height: 1.75;
    margin-bottom: 12px;
    padding: 20px 24px;
    background: var(--color-bg-alt);
    border-radius: var(--radius);
    border-left: 3px solid var(--color-accent);
}

.paper-abstract p:last-child {
    margin-bottom: 0;
}

.abstract-placeholder {
    font-style: italic;
    color: var(--color-text-muted);
}

/* ===== Teaching ===== */
.teaching-layout {
    display: grid;
    grid-template-columns: 1fr;
    gap: 24px;
}

.teaching-card {
    background: #fff;
    padding: var(--space-card);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-sm);
}

.teaching-role {
    display: flex;
    align-items: center;
    gap: 14px;
    margin-bottom: 20px;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--color-border-light);
}

.role-icon {
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 10px;
}

.instructor-icon {
    background: var(--color-accent-soft);
    color: var(--color-accent);
}

.ta-icon {
    background: var(--color-accent-soft);
    color: var(--color-accent);
}

.teaching-role h3 {
    font-family: var(--font-heading);
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--color-primary);
}

.role-count {
    font-size: 0.8rem;
    color: var(--color-text-muted);
    font-weight: 500;
}

.teaching-list {
    list-style: none;
}

.teaching-list li {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 10px 0;
    border-bottom: 1px solid var(--color-border-light);
}

.teaching-list li:last-child {
    border-bottom: none;
}

.course-info {
    display: flex;
    align-items: baseline;
    gap: 8px;
}

.course-name {
    font-weight: 500;
    color: var(--color-text);
    font-size: 0.9rem;
}

.course-level {
    font-size: 0.78rem;
    color: var(--color-text-muted);
    font-style: italic;
    white-space: nowrap;
}

.course-year {
    flex-shrink: 0;
    font-size: 0.82rem;
    font-weight: 600;
    color: var(--color-accent);
    white-space: nowrap;
}

/* ===== Service ===== */
.service-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 24px;
}

.service-card {
    background: #fff;
    padding: var(--space-card);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-sm);
}

.service-icon {
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-accent-soft);
    color: var(--color-accent);
    border-radius: 12px;
    margin-bottom: 16px;
}

.service-card h3 {
    font-family: var(--font-heading);
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: 16px;
}

.service-list {
    list-style: none;
}

.service-list li {
    padding: 10px 0;
    border-bottom: 1px solid var(--color-border-light);
}

.service-list li:last-child {
    border-bottom: none;
}

.service-name {
    font-weight: 500;
    display: block;
    color: var(--color-text);
    font-size: 0.92rem;
}

.service-detail {
    font-size: 0.82rem;
    color: var(--color-text-muted);
}

/* ===== Skills ===== */
.skills-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 24px;
}

.skill-category {
    background: #fff;
    padding: var(--space-card);
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-sm);
}

.skill-category h3 {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--color-primary);
    margin-bottom: 16px;
    padding-bottom: 12px;
    border-bottom: 1px solid var(--color-border-light);
}

.skill-category h3 svg {
    color: var(--color-accent);
}

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

.skill-badge {
    display: inline-block;
    padding: 7px 16px;
    font-size: 0.85rem;
    font-weight: 500;
    background: var(--color-bg-alt);
    color: var(--color-text-secondary);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    transition: all var(--transition);
}

.skill-badge:hover {
    border-color: var(--color-accent);
    color: var(--color-accent);
    background: var(--color-accent-soft);
    transform: translateY(-1px);
}

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

/* ===== References ===== */
.refs-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
}

.ref-card {
    display: flex;
    gap: 16px;
    background: #fff;
    padding: 24px;
    border-radius: var(--radius-lg);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition);
}

.ref-card:hover {
    box-shadow: var(--shadow-md);
    border-color: rgba(37, 99, 235, 0.2);
}

.ref-avatar {
    flex-shrink: 0;
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-primary);
    color: #fff;
    border-radius: 12px;
    font-weight: 700;
    font-size: 0.85rem;
    letter-spacing: 0.02em;
}

.ref-info h4 {
    font-family: var(--font-heading);
    font-size: 1rem;
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: 4px;
}

.ref-info p {
    font-size: 0.82rem;
    color: var(--color-text-secondary);
    line-height: 1.55;
    margin-bottom: 6px;
}

.ref-info a {
    font-size: 0.82rem;
    font-weight: 500;
}

/* ===== Footer ===== */
footer {
    background: var(--color-primary);
    color: rgba(255,255,255,0.7);
    padding: 40px 24px 24px;
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-bottom: 20px;
    border-bottom: 1px solid rgba(255,255,255,0.1);
    margin-bottom: 16px;
}

.footer-name {
    display: block;
    font-family: var(--font-heading);
    font-size: 1.1rem;
    font-weight: 700;
    color: #fff;
}

.footer-role {
    display: block;
    font-size: 0.82rem;
    margin-top: 2px;
}

.footer-links {
    display: flex;
    gap: 24px;
}

.footer-links a {
    color: rgba(255,255,255,0.7);
    font-size: 0.85rem;
    font-weight: 500;
    transition: color var(--transition);
}

.footer-links a:hover {
    color: #fff;
}

.footer-copy {
    text-align: center;
    font-size: 0.78rem;
    opacity: 0.6;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .nav-links {
        display: none;
        position: absolute;
        top: 64px;
        left: 0;
        right: 0;
        background: rgba(255,255,255,0.98);
        backdrop-filter: blur(16px);
        flex-direction: column;
        padding: 16px 24px;
        border-bottom: 1px solid var(--color-border);
        gap: 12px;
    }

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

    .nav-links a::after {
        display: none;
    }

    .nav-toggle {
        display: flex;
    }

    #hero {
        padding: 110px 20px 60px;
    }

    .hero-container {
        flex-direction: column;
        text-align: center;
    }

    .hero-image {
        width: 160px;
        height: 160px;
    }

    .hero-image-ring {
        inset: -6px;
    }

    .hero-text h1 {
        font-size: 2.2rem;
    }

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

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

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

    .hero-scroll-hint {
        display: none;
    }

    .about-grid {
        grid-template-columns: 1fr;
        gap: 28px;
    }

    .interests-grid,
    .skills-grid,
    .service-grid,
    .refs-grid {
        grid-template-columns: 1fr;
    }

    .teaching-layout {
        grid-template-columns: 1fr;
    }

    .timeline-header {
        flex-direction: column;
    }

    .timeline-meta {
        text-align: left;
    }

    .section {
        padding: var(--space-section) 16px;
    }

    .paper-title {
        font-size: 1.05rem;
    }

    .paper-item {
        padding: 24px;
    }

    .paper-badge {
        right: 20px;
    }

    .ref-card {
        flex-direction: column;
    }

    .footer-content {
        flex-direction: column;
        gap: 16px;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .hero-text h1 {
        font-size: 1.85rem;
    }

    .section-title {
        font-size: 1.6rem;
    }

    .timeline {
        padding-left: 28px;
    }

    .timeline-marker {
        left: -28px;
        width: 14px;
        height: 14px;
    }

    .timeline::before {
        left: 6px;
    }
}

/* ===== Animations ===== */
.fade-in {
    opacity: 0;
    transform: translateY(24px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

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

/* stagger children */
.fade-in:nth-child(2) { transition-delay: 0.08s; }
.fade-in:nth-child(3) { transition-delay: 0.16s; }
.fade-in:nth-child(4) { transition-delay: 0.24s; }