:root {
    /* Colors */
    --primary-color: #0056b3; /* Deep Blue */
    --accent-color: #00a8cc; /* Teal */
    --bg-color: #ffffff;
    --bg-secondary: #f8f9fa;
    --text-color: #333333;
    --text-secondary: #666666;
    --border-color: #e0e0e0;
    --card-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
    --card-shadow-hover: 0 10px 15px rgba(0, 0, 0, 0.1);
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 2rem;
    --spacing-lg: 4rem;
    --spacing-xl: 8rem;
    
    /* Typography */
    --font-main: 'Inter', sans-serif;
    --font-heading: 'Inter', sans-serif;
}

[data-theme="dark"] {
    --primary-color: #4dabf7;
    --accent-color: #22b8cf;
    --bg-color: #121212;
    --bg-secondary: #1e1e1e;
    --text-color: #e0e0e0;
    --text-secondary: #a0a0a0;
    --border-color: #333333;
    --card-shadow: 0 4px 6px rgba(0, 0, 0, 0.3);
    --card-shadow-hover: 0 10px 15px rgba(0, 0, 0, 0.5);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-main);
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

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

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

ul {
    list-style: none;
}

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

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 var(--spacing-sm);
}

/* Typography */
h1, h2, h3, h4 {
    font-family: var(--font-heading);
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: var(--spacing-sm);
}

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

.section-title {
    text-align: center;
    margin-bottom: var(--spacing-lg);
    position: relative;
    padding-bottom: var(--spacing-xs);
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 4px;
    background-color: var(--accent-color);
    border-radius: 2px;
}

/* Header */
.site-header {
    background-color: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    position: sticky;
    top: 0;
    z-index: 1000;
    border-bottom: 1px solid var(--border-color);
    padding: var(--spacing-sm) 0;
}

[data-theme="dark"] .site-header {
    background-color: rgba(18, 18, 18, 0.9);
}

.site-header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--text-color);
}

.main-nav {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.main-nav ul {
    display: flex;
    gap: var(--spacing-md);
}

.main-nav a {
    color: var(--text-color);
    font-weight: 500;
}

.main-nav a:hover {
    color: var(--primary-color);
}

#theme-toggle, #mobile-menu-btn {
    background: none;
    border: none;
    color: var(--text-color);
    cursor: pointer;
    font-size: 1.2rem;
    padding: 0.5rem;
    transition: color 0.2s;
}

#mobile-menu-btn {
    display: none;
}

/* Sections */
.section {
    padding: var(--spacing-lg) 0;
}

.hero-section {
    padding: var(--spacing-xl) 0 var(--spacing-lg);
    background: linear-gradient(135deg, var(--bg-color) 0%, var(--bg-secondary) 100%);
}

/* Hero Content */
.hero-content {
    display: flex;
    align-items: center;
    gap: var(--spacing-lg);
}

.profile-image-container {
    flex: 0 0 250px;
}

.profile-image {
    width: 250px;
    height: 250px;
    object-fit: cover;
    object-position: top; /* Adjusted to fix head cropping */
    border-radius: 50%;
    box-shadow: var(--card-shadow-hover);
    border: 4px solid var(--bg-color);
}

.profile-info h1 {
    margin-bottom: 0.5rem;
}

.chinese-name {
    font-weight: 400;
    opacity: 0.8;
}

.role {
    font-size: 1.25rem;
    font-weight: 500;
    color: var(--primary-color);
    margin-bottom: 0.25rem;
}

.institution {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
}

.social-links {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.social-links a {
    font-size: 1.5rem;
    color: var(--text-secondary);
}

.social-links a:hover {
    color: var(--primary-color);
    transform: translateY(-2px);
}

.bio-text {
    max-width: 600px;
    color: var(--text-secondary);
}

/* News */
.news-scroll {
    background-color: var(--bg-secondary);
    border-radius: 12px;
    padding: var(--spacing-md);
    max-height: 400px;
    overflow-y: auto;
}

.news-item {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
    padding-bottom: var(--spacing-sm);
    border-bottom: 1px solid var(--border-color);
}

.news-item:last-child {
    border-bottom: none;
    margin-bottom: 0;
    padding-bottom: 0;
}

.news-item .date {
    font-weight: 600;
    color: var(--primary-color);
    min-width: 80px;
}

/* Publications */
.filter-bar {
    display: flex;
    justify-content: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
    flex-wrap: wrap;
}

.filter-btn {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    padding: 0.5rem 1.5rem;
    border-radius: 20px;
    cursor: pointer;
    font-family: var(--font-main);
    color: var(--text-color);
    transition: all 0.2s;
}

.filter-btn.active, .filter-btn:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

.publications-grid {
    display: grid;
    gap: var(--spacing-md);
}

.paper-card {
    display: grid;
    grid-template-columns: 200px 1fr;
    gap: var(--spacing-md);
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: var(--spacing-md);
    transition: box-shadow 0.2s;
}

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

.paper-thumb img {
    width: 100%;
    height: auto;
    border-radius: 8px;
    object-fit: cover;
}

.paper-info h3 {
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
}

.paper-info .authors {
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
    font-size: 0.95rem;
}

.paper-info .venue {
    margin-bottom: 1rem;
    font-weight: 500;
}

.tag {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    background-color: var(--bg-secondary);
    border-radius: 4px;
    font-size: 0.85rem;
    margin-right: 0.5rem;
}

.tag.highlight {
    background-color: rgba(255, 0, 0, 0.1);
    color: #d32f2f;
}

[data-theme="dark"] .tag.highlight {
    background-color: rgba(255, 69, 69, 0.2);
    color: #ff5252;
}

.paper-links {
    display: flex;
    gap: var(--spacing-sm);
}

.btn-link {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 500;
    font-size: 0.9rem;
}

.view-all-container {
    text-align: center;
    margin-top: var(--spacing-lg);
}

.btn {
    display: inline-block;
    padding: 0.75rem 2rem;
    border-radius: 8px;
    font-weight: 600;
    transition: transform 0.2s;
}

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

.btn.primary:hover {
    background-color: var(--accent-color);
    transform: translateY(-2px);
}

/* Footer */
.site-footer {
    background-color: var(--bg-secondary);
    padding: var(--spacing-md) 0;
    text-align: center;
    color: var(--text-secondary);
    margin-top: var(--spacing-xl);
    font-size: 0.9rem;
}

/* Mobile Responsive */
@media (max-width: 768px) {
    h1 { font-size: 2rem; }
    
    .hero-content {
        flex-direction: column;
        text-align: center;
    }
    
    .social-links {
        justify-content: center;
    }
    
    .main-nav ul {
        display: none;
        flex-direction: column;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background-color: var(--bg-color);
        padding: var(--spacing-md);
        box-shadow: var(--card-shadow);
        border-bottom: 1px solid var(--border-color);
    }
    
    .main-nav.active ul {
        display: flex;
    }
    
    #mobile-menu-btn {
        display: block;
    }
    
    .paper-card {
        grid-template-columns: 1fr;
    }
    
    .paper-thumb {
        max-width: 100%;
    }
}