/* CSS Variables for consistent theming */
:root {
    --primary-color: #0078d4;
    --secondary-color: #106ebe;
    --accent-color: #40e0d0;
    --text-dark: #323130;
    --text-light: #605e5c;
    --text-muted: #8a8886;
    --background-light: #faf9f8;
    --background-white: #ffffff;
    --border-light: #edebe9;
    --shadow-light: rgba(0, 0, 0, 0.1);
    --shadow-medium: rgba(0, 0, 0, 0.15);
    --transition: all 0.3s ease;
    --border-radius: 8px;
    --max-width: 1200px;
    --section-padding: 80px 20px;
    --focus-ring: 0 0 0 3px rgba(0,120,212,0.4);
}

/* Dark theme variables (will activate when body has .dark-theme) */
body.dark-theme {
    --primary-color: #3aa9ff;
    --secondary-color: #62baff;
    --accent-color: #64ffe9;
    --text-dark: #f5f5f5;
    --text-light: #d0d0ce;
    --text-muted: #a3a19f;
    --background-light: #1f1f1f;
    --background-white: #141414;
    --border-light: #2a2a2a;
    --shadow-light: rgba(0,0,0,0.4);
    --shadow-medium: rgba(0,0,0,0.6);
}

@media (prefers-color-scheme: dark) {
    body:not(.light-forced) {
        --primary-color: #3aa9ff;
        --secondary-color: #62baff;
        --accent-color: #64ffe9;
        --text-dark: #f5f5f5;
        --text-light: #d0d0ce;
        --text-muted: #a3a19f;
        --background-light: #1f1f1f;
        --background-white: #141414;
        --border-light: #2a2a2a;
        --shadow-light: rgba(0,0,0,0.4);
        --shadow-medium: rgba(0,0,0,0.6);
    }
}

body, .research-card, .publication-card, .additional-links, .social-link, .education-item {
    transition: background-color .4s ease, color .4s ease, border-color .4s ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: var(--text-dark);
    background-color: var(--background-white);
}

/* Skip link */
.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--primary-color);
    color: #fff;
    padding: 8px 16px;
    z-index: 10000;
    border-radius: 0 0 4px 0;
    transition: top 0.2s ease;
}
.skip-link:focus { top: 0; }

/* Container */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 20px;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.2;
    margin-bottom: 1rem;
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }

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

.lead {
    font-size: 1.125rem;
    font-weight: 400;
    color: var(--text-dark);
}

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

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

/* Header and Navigation */
.header {
    background: var(--background-white);
    box-shadow: 0 2px 10px var(--shadow-light);
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
}

.nav-container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 70px;
}

.nav-brand h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
    margin: 0;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
    margin: 0;
}

.theme-toggle {
    background: var(--background-light);
    border: 1px solid var(--border-light);
    color: var(--text-dark);
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    cursor: pointer;
    margin-right: 1rem;
    transition: var(--transition);
}
.theme-toggle:hover, .theme-toggle:focus {
    background: var(--primary-color);
    color: #fff;
    box-shadow: var(--focus-ring);
}

.nav-link {
    font-weight: 500;
    color: var(--text-dark);
    padding: 0.5rem 0;
    border-bottom: 2px solid transparent;
    transition: var(--transition);
}

.nav-link:hover {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
}

.nav-link.active {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
}

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

.nav-toggle span {
    width: 25px;
    height: 3px;
    background: var(--text-dark);
    transition: var(--transition);
}

/* Hero Section */
.hero {
    padding: 120px 20px 80px;
    background: linear-gradient(135deg, var(--background-light) 0%, var(--background-white) 60%), radial-gradient(circle at 70% 30%, rgba(64,224,208,0.15), transparent 60%);
    background-blend-mode: overlay;
    position: relative;
}
body.dark-theme .hero {
    background: linear-gradient(135deg, #1a1a1a 0%, #111 60%), radial-gradient(circle at 70% 30%, rgba(58,169,255,0.15), transparent 60%);
}

.hero-content {
    display: grid;
    grid-template-columns: 1fr auto;
    gap: 3rem;
    align-items: center;
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 700;
    color: var(--text-dark);
    margin-bottom: 0.5rem;
}

.hero-subtitle {
    font-size: 1.5rem;
    font-weight: 500;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.hero-description {
    font-size: 1.125rem;
    color: var(--text-light);
    margin-bottom: 1rem;
}

.hero-tagline {
    font-style: italic;
    color: var(--text-muted);
    margin-bottom: 2rem;
    font-size: 1rem;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.hero-image {
    display: flex;
    justify-content: center;
    align-items: center;
}

.profile-image {
    width: 200px;
    height: 200px;
    border-radius: 50%;
    object-fit: cover;
    object-position: left center; /* Focus on the left side where your face is */
    border: 4px solid var(--primary-color);
    box-shadow: 0 8px 25px var(--shadow-medium);
    transition: var(--transition);
}

.profile-image:hover {
    transform: scale(1.05);
    box-shadow: 0 12px 35px var(--shadow-medium);
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 12px 24px;
    border-radius: var(--border-radius);
    font-weight: 500;
    text-align: center;
    transition: var(--transition);
    border: 2px solid transparent;
    cursor: pointer;
}

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

.btn-primary:hover {
    background: var(--secondary-color);
    color: white;
    transform: translateY(-2px);
    box-shadow: 0 4px 15px var(--shadow-medium);
}

.btn-secondary {
    background: transparent;
    color: var(--primary-color);
    border-color: var(--primary-color);
}

.btn-secondary:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-2px);
    box-shadow: 0 4px 15px var(--shadow-medium);
}

/* Sections */
.section {
    padding: var(--section-padding);
}

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

.section-title {
    text-align: center;
    margin-bottom: 3rem;
    font-size: 2.5rem;
    color: var(--text-dark);
}

/* About Section */
.about-content {
    max-width: 800px;
    margin: 0 auto;
}

.education {
    margin-top: 2rem;
}

.education h3 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.education-item {
    margin-bottom: 1.5rem;
    padding: 1.5rem;
    background: var(--background-white);
    border-radius: var(--border-radius);
    box-shadow: 0 2px 10px var(--shadow-light);
}

.education-item h4 {
    color: var(--text-dark);
    margin-bottom: 0.5rem;
}

.education-item p {
    margin-bottom: 0.25rem;
}

.education-item em {
    color: var(--text-muted);
}

/* Research Grid */
.research-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

.research-card {
    background: var(--background-white);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: 0 4px 20px var(--shadow-light);
    text-align: center;
    transition: var(--transition);
}
body.dark-theme .research-card { background: #1e1e1e; }

.research-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 30px var(--shadow-medium);
}

.research-icon {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.research-card h3 {
    color: var(--text-dark);
    margin-bottom: 1rem;
}

/* Publications Section */
.publications-header {
    text-align: center;
    margin-bottom: 2rem;
}

.publications-description {
    max-width: 600px;
    margin: 0 auto 2rem;
    font-size: 1.1rem;
    color: var(--text-light);
}

.publications-grid {
    display: grid;
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.publication-card {
    background: var(--background-white);
    border: 1px solid var(--border-light);
    border-radius: var(--border-radius);
    padding: 1.5rem;
    transition: var(--transition);
    position: relative;
}
body.dark-theme .publication-card { background:#1e1e1e; border-color:#2a2a2a; }

.publication-card:hover {
    box-shadow: 0 4px 20px var(--shadow-light);
    transform: translateY(-2px);
}

.publication-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-dark);
    margin-bottom: 0.5rem;
    line-height: 1.4;
}

.publication-title a {
    color: inherit;
    text-decoration: none;
}

.publication-title a:hover {
    color: var(--primary-color);
}

.publication-authors {
    color: var(--text-light);
    margin-bottom: 0.5rem;
    font-size: 0.95rem;
}

.publication-authors .author-highlight {
    font-weight: 600;
    color: var(--text-dark);
}

.publication-venue {
    color: var(--text-muted);
    font-style: italic;
    margin-bottom: 0.75rem;
    font-size: 0.9rem;
}

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

.publication-year {
    background: var(--background-light);
    color: var(--text-dark);
    padding: 0.25rem 0.75rem;
    border-radius: 15px;
    font-size: 0.85rem;
    font-weight: 500;
}

.publication-citations {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-muted);
    font-size: 0.9rem;
}

.citation-count {
    background: var(--primary-color);
    color: white;
    padding: 0.2rem 0.6rem;
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 500;
}

.publication-links {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.publication-link {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    padding: 0.4rem 0.8rem;
    background: var(--background-light);
    color: var(--text-dark);
    border-radius: 15px;
    font-size: 0.85rem;
    text-decoration: none;
    transition: var(--transition);
}

.publication-link:hover {
    background: var(--primary-color);
    color: white;
}

.publication-link i {
    font-size: 0.8rem;
}

.publications-footer {
    text-align: center;
    margin-top: 3rem;
}

.publications-footer .btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

/* Publication Abstract */
.publication-abstract {
    color: var(--text-light);
    font-size: 0.9rem;
    line-height: 1.5;
    margin: 0.75rem 0;
    padding: 0.75rem;
    background: var(--background-light);
    border-radius: 4px;
    border-left: 3px solid var(--primary-color);
}
body.dark-theme .publication-abstract { background:#222; }

/* Contact Section */
.contact-content {
    display: grid;
    grid-template-columns: 1fr auto;
    gap: 3rem;
    max-width: 800px;
    margin: 0 auto;
}

.contact-item {
    display: flex;
    gap: 1rem;
    margin-bottom: 2rem;
    align-items: flex-start;
}

.contact-item i {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-top: 0.25rem;
}

.contact-item h3 {
    color: var(--text-dark);
    margin-bottom: 0.5rem;
}

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

.social-link {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem;
    background: var(--background-white);
    border-radius: var(--border-radius);
    box-shadow: 0 2px 10px var(--shadow-light);
    transition: var(--transition);
}
body.dark-theme .social-link { background:#1e1e1e; }

.social-link:hover {
    transform: translateX(5px);
    box-shadow: 0 4px 15px var(--shadow-medium);
}

.social-link i {
    font-size: 1.25rem;
    color: var(--primary-color);
}

.additional-links {
    background: var(--background-white);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: 0 4px 20px var(--shadow-light);
}
body.dark-theme .additional-links { background:#1e1e1e; }

.additional-links h3 {
    color: var(--text-dark);
    margin-bottom: 1rem;
}

.additional-links ul {
    list-style: none;
}

.additional-links li {
    margin-bottom: 0.5rem;
}

.additional-links a {
    display: block;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-light);
    transition: var(--transition);
}

.additional-links a:hover {
    padding-left: 1rem;
    background: var(--background-light);
}

/* Placeholder (future) resource cards */
.resource-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 1rem;
    margin-top: 1rem;
}
.resource-card {
    background: var(--background-light);
    padding: 1rem;
    border-radius: var(--border-radius);
    text-align: center;
    transition: var(--transition);
    border: 1px solid var(--border-light);
}
body.dark-theme .resource-card { background:#1e1e1e; }
.resource-card:hover { transform: translateY(-4px); box-shadow: 0 4px 15px var(--shadow-light); }
.resource-card i { font-size:1.5rem; color: var(--primary-color); margin-bottom: .5rem; }

/* Improved focus ring */
*:focus-visible { outline: none; box-shadow: var(--focus-ring); }

/* Footer */
.footer {
    background: var(--text-dark);
    color: white;
    text-align: center;
    padding: 2rem 20px;
}
body.dark-theme .footer { background:#111; }

.footer p {
    color: #ccc;
    margin-bottom: 0.5rem;
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        display: none;
    }
    
    .nav-toggle {
        display: flex;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .research-grid {
        grid-template-columns: 1fr;
    }
    
    .publications-grid {
        grid-template-columns: 1fr;
    }
    
    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .contact-content {
        grid-template-columns: 1fr;
    }
    
    .social-links {
        flex-direction: row;
        flex-wrap: wrap;
    }
    
    .hero-buttons {
        justify-content: center;
    }
    
    .section {
        padding: 60px 20px;
    }
    
    .section-title {
        font-size: 2rem;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }
    
    .hero-subtitle {
        font-size: 1.25rem;
    }
    
    .image-placeholder {
        width: 150px;
        height: 150px;
        font-size: 3rem;
    }
    
    .btn {
        padding: 10px 20px;
        font-size: 0.9rem;
    }
    
    .research-card {
        padding: 1.5rem;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
        gap: 0.75rem;
    }
    
    .stat-item {
        padding: 1rem;
    }
    
    .stat-number {
        font-size: 1.5rem;
    }
}

/* Animation for smooth loading */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.hero-content > * {
    animation: fadeInUp 0.8s ease-out;
}

.research-card {
    animation: fadeInUp 0.8s ease-out;
}

/* Accessibility improvements */
@media (prefers-reduced-motion: reduce) {
    * {
        animation: none !important;
        transition: none !important;
    }
}

/* Focus styles for accessibility */
a:focus,
.btn:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* Print styles */
@media print {
    .header,
    .nav,
    .hero-buttons,
    .footer {
        display: none;
    }
    
    .section {
        page-break-inside: avoid;
    }
}