:root {
    --primary: #1a1a1a;
    --secondary: #666;
    --accent: #2563eb;
    --light-gray: #f8f9fa;
    --border: #e5e7eb;
    --text: #333;
    --text-light: #6b7280;
    --bg: #ffffff;
    --shadow: 0 1px 3px rgba(0,0,0,0.1);
    --radius: 8px;
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'SF Mono', Monaco, Consolas, monospace;
    --max-width: 900px;
    --spacing: 1.5rem;
}

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

body {
    font-family: var(--font-sans);
    line-height: 1.6;
    color: var(--text);
    background: var(--bg);
    font-size: 15px;
}

/* Navigation */
.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border);
    z-index: 1000;
    padding: 0.75rem 0;
}

.nav-container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
    align-items: center;
}

.nav-link {
    text-decoration: none;
    color: var(--text);
    font-weight: 500;
    font-size: 14px;
    transition: color 0.2s;
    position: relative;
}

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

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -8px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--accent);
    border-radius: 1px;
}

.lang-switcher {
    display: flex;
    gap: 0.5rem;
}

.lang-btn {
    padding: 0.25rem 0.5rem;
    border: 1px solid var(--border);
    background: none;
    cursor: pointer;
    border-radius: 4px;
    font-size: 12px;
    font-weight: 500;
    transition: all 0.2s;
}

.lang-btn.active {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
}

.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
    gap: 3px;
}

.hamburger span {
    width: 20px;
    height: 2px;
    background: var(--text);
    transition: 0.3s;
}

/* Main Content */
main {
    margin-top: 60px;
}

.section {
    padding: 1rem 0;
    max-width: var(--max-width);
    margin: 0 auto;
    padding-left: 1rem;
    padding-right: 1rem;
}

.section-title {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 2rem;
    color: var(--primary);
    position: relative;
    padding-bottom: 0.5rem;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 40px;
    height: 2px;
    background: var(--accent);
}

/* Hero Section - Academic Style */
.hero {
    padding: 4rem 0 3rem;
    background: white;
    border-bottom: 1px solid var(--border);
}

.hero-content {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1rem;
    display: grid;
    grid-template-columns: auto 1fr;
    gap: 2.5rem;
    align-items: center;
}

.hero-photo {
    width: 150px;
    height: 150px;
    border-radius: 50%;
    object-fit: cover;
    border: 3px solid var(--accent);
    box-shadow: var(--shadow);
}

.hero-info h1 {
    font-size: 2.25rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: var(--primary);
}

.hero-info .subtitle {
    font-size: 1.1rem;
    color: var(--accent);
    font-weight: 600;
    margin-bottom: 1rem;
}

.hero-info .description {
    font-size: 1rem;
    color: var(--text-light);
    line-height: 1.6;
    margin-bottom: 1.5rem;
    max-width: 500px;
}

.hero-links {
    display: flex;
    gap: 1rem;
    align-items: center;
}

.hero-links a {
    color: var(--text-light);
    text-decoration: none;
    font-size: 1.1rem;
    transition: color 0.2s;
}

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

.btn {
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius);
    text-decoration: none;
    font-weight: 500;
    font-size: 14px;
    transition: all 0.2s;
    border: 1px solid transparent;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

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

.btn-primary:hover {
    background: #1d4ed8;
    transform: translateY(-1px);
}

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

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

/* About Section */
.about-grid {
    display: grid;
    grid-template-columns: 1fr auto;
    gap: 3rem;
    align-items: start;
}

.about-text p {
    margin-bottom: 1rem;
    color: var(--text-light);
}

.stat-item {
    text-align: center;
    padding: 1rem;
    background: var(--light-gray);
    border-radius: var(--radius);
    border: 1px solid var(--border);
}

.stat-number {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent);
}

.stat-label {
    font-size: 12px;
    color: var(--text-light);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-top: 0.25rem;
}

/* Timeline */
.timeline {
    position: relative;
    padding-left: 2rem;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 0.75rem;
    top: 0;
    bottom: 0;
    width: 2px;
    background: var(--border);
}

.timeline-item {
    position: relative;
    margin-bottom: 2rem;
    padding-left: 2rem;
}

.timeline-item::before {
    content: '';
    position: absolute;
    left: -0.375rem;
    top: 0.375rem;
    width: 8px;
    height: 8px;
    background: var(--accent);
    border-radius: 50%;
    border: 2px solid white;
    box-shadow: var(--shadow);
}

.timeline-date {
    font-size: 12px;
    color: var(--text-light);
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    margin-bottom: 0.5rem;
}

.timeline-content h3 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 0.25rem;
    color: var(--primary);
}

.institution {
    font-size: 14px;
    color: var(--accent);
    font-weight: 500;
    margin-bottom: 0.5rem;
}

.description {
    font-size: 14px;
    color: var(--text-light);
    line-height: 1.5;
}

/* Grid Layouts */
.grid {
    display: grid;
    gap: 1.5rem;
}

.grid-2 {
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.grid-3 {
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
}

/* Cards */
.card {
    background: white;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.5rem;
    transition: all 0.2s;
}

.card:hover {
    border-color: var(--accent);
    box-shadow: var(--shadow);
}

.card h3, .card h4 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
    color: var(--primary);
}

.card p {
    font-size: 14px;
    color: var(--text-light);
    line-height: 1.5;
}

/* Research Section Improvements */
.research-subsection {
    margin-bottom: 3rem;
}

.research-subsection:last-child {
    margin-bottom: 0;
}

.project-item {
    margin-bottom: 1rem;
}

.subsection-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 1.5rem;
    color: var(--primary);
    position: relative;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--border);
}

.subsection-title::before {
    content: '';
    position: absolute;
    bottom: -1px;
    left: 0;
    width: 60px;
    height: 2px;
    background: var(--accent);
}

.subsection-text {
    color: var(--text-light);
}

/* Publications */
.publication-item {
    padding: 1.5rem 0;
    border-bottom: 1px solid var(--border);
}

.publication-item:first-child {
    padding-top: 0;
}

.publication-item:last-child {
    border-bottom: none;
}

.publication-item h3 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--primary);
}

.authors {
    font-size: 14px;
    margin-bottom: 0.25rem;
}

.venue {
    font-size: 14px;
    color: var(--accent);
    font-weight: 500;
    margin-bottom: 0.5rem;
}

.keywords {
    margin-top: 0.75rem;
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.keyword {
    font-size: 11px;
    padding: 0.25rem 0.5rem;
    background: var(--light-gray);
    color: var(--text-light);
    border-radius: 12px;
    border: 1px solid var(--border);
    text-transform: uppercase;
    letter-spacing: 0.25px;
}

/* Publication and Education Links */
.publication-links {
    margin-top: 0.5rem;
}

.pub-link {
    color: var(--accent);
    text-decoration: none;
    font-size: 13px;
    font-weight: 500;
    transition: color 0.2s ease;
}

.pub-link:hover {
    color: #1d4ed8;
    text-decoration: underline;
}

.pub-link i {
    font-size: 11px;
    margin-right: 0.25rem;
}

.teaching-item {
    border: 0.5px solid var(--border);
    border-radius: var(--radius);
    padding: 1rem;
}

/* Contact */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 3rem;
}

.contact-info {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.contact-item {
    display: flex;
    align-items: flex-start;
    gap: 1rem;
}

.contact-item i {
    width: 20px;
    color: var(--accent);
    margin-top: 0.125rem;
}

.contact-item div h4 {
    font-size: 14px;
    font-weight: 600;
    margin-bottom: 0.25rem;
    color: var(--primary);
}

.contact-item div p {
    font-size: 14px;
    color: var(--text-light);
}

.contact-form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.form-group label {
    font-size: 14px;
    font-weight: 500;
    color: var(--text);
}

.form-group input,
.form-group textarea {
    padding: 0.75rem;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    font-family: inherit;
    font-size: 14px;
    transition: border-color 0.2s;
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--accent);
}

.form-group textarea {
    resize: vertical;
    min-height: 120px;
}

/* Footer */
.footer {
    background: var(--light-gray);
    border-top: 1px solid var(--border);
    padding: 2rem 0;
    text-align: center;
}

.footer p {
    font-size: 14px;
    color: var(--text-light);
}

/* Color Picker Styles */
.nav-tools {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.color-picker-container {
    position: relative;
    display: flex;
    align-items: center;
}

.color-picker-btn {
    width: 36px;
    height: 36px;
    border: 0px;
    background: var(--bg);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
    color: var(--text-light);
}

.color-picker-btn:hover {
    border-color: var(--accent);
    background: var(--light-gray);
    color: var(--accent);
}

.color-picker {
    position: absolute;
    top: 0;
    left: 0;
    width: 36px;
    height: 36px;
    opacity: 0;
    cursor: pointer;
    border: none;
    border-radius: 6px;
}

.color-picker::-webkit-color-swatch-wrapper {
    padding: 0;
    border: none;
    border-radius: 6px;
}

.color-picker::-webkit-color-swatch {
    border: none;
    border-radius: 6px;
}

.color-picker::-moz-color-swatch {
    border: none;
    border-radius: 6px;
}

/* Responsive Design */
@media (max-width: 768px) {
    .hamburger {
        display: flex;
    }

    .nav-menu {
        position: fixed;
        top: 60px;
        left: -100%;
        width: 100%;
        height: calc(100vh - 60px);
        background: white;
        flex-direction: column;
        justify-content: flex-start;
        align-items: center;
        padding-top: 2rem;
        transition: left 0.3s;
        box-shadow: var(--shadow);
    }

    .nav-menu.active {
        left: 0;
    }

    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
        gap: 2rem;
    }

    .hero-photo {
        justify-self: center;
        width: 120px;
        height: 120px;
    }    .hero-info h1 {
        font-size: 1.75rem;
    }

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

    .about-grid {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .about-stats {
        flex-direction: row;
        justify-content: center;
    }

    .contact-grid {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .section {
        padding: 2rem 0;
    }

    .timeline {
        padding-left: 1.5rem;
    }

    .timeline-item {
        padding-left: 1.5rem;
    }
}

@media (max-width: 480px) {
    .hero {
        padding: 3rem 0;
    }

    .section {
        padding-left: 0.75rem;
        padding-right: 0.75rem;
    }

    .nav-container {
        padding: 0 0.75rem;
    }

    .card {
        padding: 1rem;
    }

    .hero-photo {
        width: 100px;
        height: 100px;
    }

    .hero-info h1 {
        font-size: 1.5rem;
    }
}

/* Smooth scrolling */
html {
    scroll-behavior: smooth;
}

/* Focus styles */
*:focus {
    outline: none;
}

button:focus,
.btn:focus,
.lang-btn:focus,
input:focus,
textarea:focus {
    outline: none !important;
    box-shadow: none !important;
}

/* Print styles */
@media print {
    .navbar, .footer {
        display: none;
    }
    
    main {
        margin-top: 0;
    }
}