:root {
    --primary-color: #0070f3;
    --secondary-color: #4a5568;
    --background-color: #ffffff;
    --text-color: #2d3748;
    --gray-light: #f7fafc;
    --gray-dark: #4a5568;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

/* Reset and base styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', system-ui, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1rem;
}

/* Header Styles */
.site-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    z-index: 1000;
    transition: all 0.3s ease;
}

.site-header.scrolled {
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

.nav-menu {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 0;
    height: 4rem;
}

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    text-decoration: none;
    background: linear-gradient(to right, #0070f3, #6b46c1);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    transition: transform 0.3s ease;
}

.logo:hover {
    transform: scale(1.05);
}

.menu-items {
    display: flex;
    gap: 2rem;
}

.nav-link {
    text-decoration: none;
    color: #4a5568;
    font-weight: 500;
    transition: color 0.3s ease;
    position: relative;
}

.nav-link:after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 100%;
    height: 2px;
    background: linear-gradient(to right, #0070f3, #6b46c1);
    opacity: 0;
    transform: scaleX(0);
    transition: all 0.3s ease;
}

.nav-link:hover:after,
.nav-link.active:after {
    opacity: 1;
    transform: scaleX(1);
}

.social-links {
    display: flex;
    gap: 1rem;
}

.social-link {
    color: #4a5568;
    transition: all 0.3s ease;
    padding: 0.5rem;
    border-radius: 50%;
}

.social-link:hover {
    color: #0070f3;
    transform: translateY(-2px);
}

.mobile-menu-button {
    display: none;
    background: none;
    border: none;
    color: #4a5568;
    font-size: 1.5rem;
    cursor: pointer;
    padding: 0.5rem;
}

.mobile-menu {
    display: none;
    position: fixed;
    top: 4rem;
    left: 0;
    right: 0;
    background: white;
    padding: 1rem 0;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    transform: translateY(-100%);
    transition: transform 0.3s ease;
}

.mobile-menu.active {
    transform: translateY(0);
}

.mobile-link {
    display: block;
    padding: 0.75rem 1rem;
    color: #4a5568;
    text-decoration: none;
    transition: background-color 0.3s ease;
}

.mobile-link:hover {
    background-color: #f7fafc;
    color: #0070f3;
}

@media (max-width: 768px) {
    .menu-items {
        display: none;
    }

    .mobile-menu-button {
        display: block;
    }

    .mobile-menu {
        display: block;
    }
}

/* Dark mode styles */
@media (prefers-color-scheme: dark) {
    .site-header {
        background: rgba(17, 24, 39, 0.9);
    }

    .nav-link {
        color: #e5e7eb;
    }

    .social-link {
        color: #e5e7eb;
    }

    .mobile-menu {
        background: #1f2937;
    }

    .mobile-link {
        color: #e5e7eb;
    }

    .mobile-link:hover {
        background-color: #374151;
    }
}

/* Hero section */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    background: linear-gradient(135deg, var(--gray-light), #fff);
    padding-top: 80px;
}

.hero-content {
    text-align: center;
    max-width: 800px;
    margin: 0 auto;
}

.hero h1 {
    font-size: 3.5rem;
    font-weight: bold;
    margin-bottom: 1rem;
    background: linear-gradient(135deg, var(--primary-color), #6b46c1);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

/* Research section */
.research {
    padding: 5rem 0;
    background: var(--background-color);
}

.research-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    padding: 2rem 0;
}

.research-card {
    padding: 2rem;
    background: white;
    border-radius: 1rem;
    box-shadow: var(--shadow);
    transition: transform 0.3s ease;
}

.research-card:hover {
    transform: translateY(-5px);
}

/* Publications section */
.publications {
    padding: 5rem 0;
    background: var(--gray-light);
}

.publication-card {
    background: white;
    padding: 2rem;
    margin-bottom: 1.5rem;
    border-radius: 1rem;
    box-shadow: var(--shadow);
}

/* Teaching section */
.teaching {
    padding: 5rem 0;
    background: var(--background-color);
}

.teaching-card {
    background: white;
    padding: 2rem;
    margin-bottom: 2rem;
    border-radius: 1rem;
    box-shadow: var(--shadow);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    padding: 0.75rem 1.5rem;
    border-radius: 0.5rem;
    font-weight: 500;
    text-decoration: none;
    transition: transform 0.3s ease;
    margin: 0.5rem;
}

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

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

.btn:hover {
    transform: translateY(-2px);
}

/* Footer Styles */
.site-footer {
    background-color: #1a202c;
    color: #fff;
    padding: 3rem 0;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 2rem;
    padding-bottom: 2rem;
    margin-bottom: 2rem;
    border-bottom: 1px solid #2d3748;
}

.footer-about {
    max-width: 24rem;
}

.gradient-text {
    font-size: 1.5rem;
    font-weight: bold;
    background: linear-gradient(to right, #60a5fa, #a78bfa);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: 1rem;
}

.footer-description {
    color: #9ca3af;
    margin-bottom: 1.5rem;
    line-height: 1.6;
}

.footer-social {
    display: flex;
    gap: 1.5rem;
    margin-top: 1.5rem;
}

.social-icon-link {
    width: 2.5rem;
    height: 2.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: #2d3748;
    color: #9ca3af;
    border-radius: 9999px;
    transition: all 0.3s ease;
}

.social-icon-link:hover {
    background-color: #3b82f6;
    color: white;
    transform: translateY(-3px);
}

.footer-section h5 {
    color: white;
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 1rem;
}

.footer-links,
.contact-info {
    list-style: none;
    padding: 0;
    margin: 0;
}

.footer-links li,
.contact-info li {
    margin-bottom: 0.5rem;
}

.footer-link {
    color: #9ca3af;
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer-link:hover {
    color: white;
}

.contact-info li {
    color: #9ca3af;
}

.mt-4 {
    margin-top: 1rem;
}

.footer-bottom {
    padding-top: 2rem;
}

.footer-bottom-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.copyright {
    color: #9ca3af;
    font-size: 0.875rem;
}

.legal-links {
    display: flex;
    gap: 1.5rem;
}

.legal-link {
    color: #9ca3af;
    text-decoration: none;
    font-size: 0.875rem;
    transition: color 0.3s ease;
}

.legal-link:hover {
    color: white;
}

/* Responsive Design */
@media (max-width: 768px) {
    .footer-grid {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .footer-about {
        max-width: none;
    }

    .footer-social {
        justify-content: center;
    }

    .footer-bottom-content {
        flex-direction: column;
        text-align: center;
    }

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

/* Dark Mode Support */
@media (prefers-color-scheme: dark) {
    .site-footer {
        background-color: #111827;
    }

    .footer-bottom {
        border-color: #374151;
    }

    .social-icon-link {
        background-color: #374151;
    }

    .social-icon-link:hover {
        background-color: #3b82f6;
    }
}