/* CSS Variables */
:root {
    /* Colors - Light Mode */
    --color-bg: #faf9f7;
    --color-bg-alt: #f0eeeb;
    --color-surface: #ffffff;
    --color-text: #1a1a1a;
    --color-text-muted: #5a5a5a;
    --color-accent: #2d5a4a;
    --color-accent-light: #3d7a6a;
    --color-border: #e0ddd8;
    --color-highlight: #e8f4f0;
    
    /* Typography */
    --font-serif: 'Crimson Pro', Georgia, serif;
    --font-sans: 'Source Sans 3', -apple-system, BlinkMacSystemFont, sans-serif;
    
    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 2rem;
    --space-xl: 4rem;
    --space-2xl: 6rem;
    
    /* Layout */
    --container-width: 900px;
    --nav-height: 60px;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 300ms ease;
}

/* Dark Mode */
[data-theme="dark"] {
    --color-bg: #121212;
    --color-bg-alt: #1a1a1a;
    --color-surface: #1e1e1e;
    --color-text: #e8e6e3;
    --color-text-muted: #a0a0a0;
    --color-accent: #5db89a;
    --color-accent-light: #7dcdb2;
    --color-border: #2a2a2a;
    --color-highlight: #1a2d26;
}

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

html {
    scroll-behavior: smooth;
    scroll-padding-top: var(--nav-height);
}

body {
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-text);
    background-color: var(--color-bg);
    transition: background-color var(--transition-normal), color var(--transition-normal);
}

/* Typography */
h1, h2, h3, h4 {
    font-family: var(--font-serif);
    font-weight: 600;
    line-height: 1.3;
}

h1 { font-size: 3rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.25rem; }

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

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

strong {
    font-weight: 600;
}

em {
    font-style: italic;
}

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

/* Navigation */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--nav-height);
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    z-index: 1000;
    transition: background-color var(--transition-normal), border-color var(--transition-normal);
}

.nav-container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 var(--space-lg);
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    font-family: var(--font-serif);
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--color-text);
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--space-lg);
}

.nav-menu a {
    color: var(--color-text-muted);
    font-size: 0.9rem;
    font-weight: 400;
    letter-spacing: 0.02em;
}

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

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-sm);
}

.nav-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-text);
    transition: var(--transition-fast);
}

.theme-toggle {
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-sm);
    color: var(--color-text-muted);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: color var(--transition-fast);
}

.theme-toggle:hover {
    color: var(--color-accent);
}

.moon-icon { display: none; }

[data-theme="dark"] .sun-icon { display: none; }
[data-theme="dark"] .moon-icon { display: block; }

/* Hero Section */
.hero {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    padding: var(--space-2xl) var(--space-lg);
    padding-top: calc(var(--nav-height) + var(--space-2xl));
    background: 
        radial-gradient(ellipse at 20% 30%, var(--color-highlight) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 70%, var(--color-highlight) 0%, transparent 50%),
        var(--color-bg);
    position: relative;
}

.hero-content {
    text-align: center;
    max-width: 700px;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--space-lg);
}

/* Profile Photo */
.hero-photo {
    width: 180px;
    height: 180px;
    border-radius: 50%;
    overflow: hidden;
    border: 4px solid var(--color-surface);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
}

.profile-img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.hero-name {
    font-size: clamp(2.5rem, 8vw, 4rem);
    margin-bottom: var(--space-sm);
    letter-spacing: -0.02em;
}

.hero-title {
    font-size: 1.5rem;
    color: var(--color-accent);
    margin-bottom: var(--space-sm);
    font-weight: 400;
}

.hero-subtitle {
    color: var(--color-text-muted);
    font-size: 1rem;
    letter-spacing: 0.1em;
    margin-bottom: var(--space-xl);
}

.hero-links {
    display: flex;
    justify-content: center;
    gap: var(--space-lg);
    flex-wrap: wrap;
}

.hero-link {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    color: var(--color-text-muted);
    font-size: 0.95rem;
    padding: var(--space-sm) var(--space-md);
    border: 1px solid var(--color-border);
    border-radius: 4px;
    transition: all var(--transition-fast);
}

.hero-link:hover {
    color: var(--color-accent);
    border-color: var(--color-accent);
    background: var(--color-highlight);
}

.hero-scroll {
    position: absolute;
    bottom: var(--space-lg);
    animation: bounce 2s infinite;
}

.hero-scroll a {
    color: var(--color-text-muted);
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% { transform: translateY(0); }
    40% { transform: translateY(-10px); }
    60% { transform: translateY(-5px); }
}

/* Sections */
.section {
    padding: var(--space-2xl) 0;
}

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

.section-title {
    font-size: 1.75rem;
    margin-bottom: var(--space-xl);
    position: relative;
    display: inline-block;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -8px;
    left: 0;
    width: 40px;
    height: 3px;
    background: var(--color-accent);
}

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

.about-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
}

.about-list li {
    position: relative;
    padding-left: var(--space-lg);
    color: var(--color-text-muted);
}

.about-list li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 10px;
    width: 8px;
    height: 8px;
    background: var(--color-accent);
    border-radius: 50%;
}

.about-list strong {
    color: var(--color-text);
}

/* Timeline */
.timeline {
    position: relative;
    padding-left: var(--space-lg);
}

.timeline::before {
    content: '';
    position: absolute;
    left: 5px;
    top: 8px;
    bottom: 8px;
    width: 2px;
    background: var(--color-border);
}

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

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

.timeline-marker {
    position: absolute;
    left: calc(-1 * var(--space-lg) + 1px);
    top: 8px;
    width: 10px;
    height: 10px;
    background: var(--color-accent);
    border-radius: 50%;
    border: 2px solid var(--color-bg);
}

.section-alt .timeline-marker {
    border-color: var(--color-bg-alt);
}

.timeline-content {
    background: var(--color-surface);
    padding: var(--space-lg);
    border-radius: 8px;
    border: 1px solid var(--color-border);
}

.timeline-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    flex-wrap: wrap;
    gap: var(--space-sm);
    margin-bottom: var(--space-sm);
}

.timeline-header h3 {
    font-size: 1.15rem;
}

.timeline-date {
    font-size: 0.85rem;
    color: var(--color-accent);
    font-weight: 500;
}

.timeline-subtitle {
    font-size: 0.95rem;
    color: var(--color-text-muted);
    margin-bottom: var(--space-xs);
}

.timeline-location {
    font-size: 0.85rem;
    color: var(--color-text-muted);
    margin-bottom: var(--space-md);
}

.timeline-detail {
    font-size: 0.9rem;
    color: var(--color-text-muted);
    margin-bottom: var(--space-xs);
}

.timeline-list {
    list-style: disc;
    padding-left: var(--space-lg);
    margin-top: var(--space-md);
}

.timeline-list li {
    font-size: 0.9rem;
    color: var(--color-text-muted);
    margin-bottom: var(--space-sm);
}

/* Skills Grid */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--space-md);
}

.skill-card {
    background: var(--color-surface);
    padding: var(--space-lg);
    border-radius: 8px;
    border: 1px solid var(--color-border);
    transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.skill-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
}

.skill-card h3 {
    font-size: 1rem;
    margin-bottom: var(--space-sm);
    color: var(--color-accent);
}

.skill-card p {
    font-size: 0.9rem;
    color: var(--color-text-muted);
    line-height: 1.5;
}

/* Publications */
.publications-summary {
    margin-bottom: var(--space-xl);
    font-size: 1.1rem;
}

.publications-categories {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
}

.publication-category {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    overflow: hidden;
}

.category-header {
    width: 100%;
    display: flex;
    align-items: center;
    gap: var(--space-md);
    padding: var(--space-md) var(--space-lg);
    background: none;
    border: none;
    cursor: pointer;
    text-align: left;
    transition: background var(--transition-fast);
}

.category-header:hover {
    background: var(--color-highlight);
}

.category-header h3 {
    flex: 1;
    font-size: 1rem;
    color: var(--color-text);
}

.category-count {
    font-size: 0.8rem;
    color: var(--color-text-muted);
    background: var(--color-bg-alt);
    padding: 2px 10px;
    border-radius: 12px;
}

.chevron {
    color: var(--color-text-muted);
    transition: transform var(--transition-fast);
}

.category-header[aria-expanded="true"] .chevron {
    transform: rotate(180deg);
}

.category-content {
    max-height: 0;
    overflow: hidden;
    transition: max-height var(--transition-normal);
}

.category-content.expanded {
    max-height: 2000px;
}

.publication-list {
    padding: var(--space-md) var(--space-lg) var(--space-lg);
    padding-left: calc(var(--space-lg) + var(--space-lg));
}

.publication-list li {
    font-size: 0.9rem;
    color: var(--color-text-muted);
    margin-bottom: var(--space-md);
    line-height: 1.6;
}

.publication-list li:last-child {
    margin-bottom: 0;
}

.publication-list strong {
    color: var(--color-text);
}

.publication-list em {
    color: var(--color-accent);
}

.publication-list a {
    color: var(--color-text-muted);
    text-decoration: none;
    transition: color var(--transition-fast);
}

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

.publication-list a strong {
    color: var(--color-text);
}

.publication-list a em {
    color: var(--color-accent);
}

/* Featured Paper */
.featured-paper {
    margin: var(--space-md) var(--space-lg);
    padding: var(--space-lg);
    background: var(--color-highlight);
    border-radius: 8px;
    border-left: 4px solid var(--color-accent);
}

.featured-paper h4 {
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--color-accent);
    margin-bottom: var(--space-sm);
}

.featured-citation {
    font-size: 0.9rem;
    line-height: 1.6;
    color: var(--color-text-muted);
    margin-bottom: var(--space-md);
}

.featured-citation strong {
    color: var(--color-text);
}

.featured-citation em {
    color: var(--color-accent);
}

.paper-link {
    display: inline-block;
    margin-left: var(--space-sm);
    padding: 2px 8px;
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--color-accent);
    border: 1px solid var(--color-accent);
    border-radius: 4px;
    text-decoration: none;
    transition: all var(--transition-fast);
}

.paper-link:hover {
    background: var(--color-accent);
    color: white;
}

.featured-abstract {
    font-size: 0.85rem;
    line-height: 1.7;
    color: var(--color-text-muted);
}

.featured-abstract strong {
    color: var(--color-text);
}

/* Scholar Link in Publications Summary */
.scholar-link {
    display: inline-flex;
    align-items: center;
    gap: var(--space-xs);
    color: var(--color-accent);
}

.scholar-link svg {
    vertical-align: middle;
}

/* Timeline Links */
.timeline-header h3 a {
    color: var(--color-text);
    text-decoration: none;
    transition: color var(--transition-fast);
}

.timeline-header h3 a:hover {
    color: var(--color-accent);
}

.timeline-subtitle a {
    color: var(--color-text-muted);
    text-decoration: none;
    transition: color var(--transition-fast);
}

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

/* Award Links */
.award-card h3 a {
    color: var(--color-text);
    text-decoration: none;
    transition: color var(--transition-fast);
}

.award-card h3 a:hover {
    color: var(--color-accent);
}

/* Awards */
.awards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--space-lg);
}

.award-card {
    background: var(--color-surface);
    padding: var(--space-lg);
    border-radius: 8px;
    border: 1px solid var(--color-border);
    text-align: center;
}

.award-amount {
    font-family: var(--font-serif);
    font-size: 2rem;
    font-weight: 600;
    color: var(--color-accent);
    margin-bottom: var(--space-sm);
}

.award-card h3 {
    font-size: 1rem;
    margin-bottom: var(--space-sm);
}

.award-card p {
    font-size: 0.85rem;
    color: var(--color-text-muted);
}

/* Footer */
.footer {
    padding: var(--space-xl) 0;
    text-align: center;
    color: var(--color-text-muted);
    font-size: 0.9rem;
    border-top: 1px solid var(--color-border);
}

/* Responsive Design */
@media (max-width: 768px) {
    :root {
        --space-lg: 1.5rem;
        --space-xl: 3rem;
        --space-2xl: 4rem;
    }
    
    h1 { font-size: 2.5rem; }
    h2 { font-size: 1.75rem; }
    
    .nav-menu {
        position: fixed;
        top: var(--nav-height);
        left: 0;
        right: 0;
        background: var(--color-bg);
        flex-direction: column;
        padding: var(--space-lg);
        gap: var(--space-md);
        border-bottom: 1px solid var(--color-border);
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: all var(--transition-normal);
    }
    
    .nav-menu.active {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }
    
    .nav-toggle {
        display: flex;
    }
    
    .nav-toggle.active span:nth-child(1) {
        transform: rotate(45deg) translate(5px, 5px);
    }
    
    .nav-toggle.active span:nth-child(2) {
        opacity: 0;
    }
    
    .nav-toggle.active span:nth-child(3) {
        transform: rotate(-45deg) translate(5px, -5px);
    }
    
    .hero {
        padding-top: calc(var(--nav-height) + var(--space-xl));
    }
    
    .hero-photo {
        width: 140px;
        height: 140px;
    }
    
    .hero-links {
        gap: var(--space-sm);
    }
    
    .hero-link {
        padding: var(--space-xs) var(--space-sm);
        font-size: 0.8rem;
    }
    
    .featured-paper {
        margin: var(--space-sm) var(--space-md);
        padding: var(--space-md);
    }
    
    .timeline {
        padding-left: var(--space-md);
    }
    
    .timeline-marker {
        left: calc(-1 * var(--space-md) + 1px);
    }
    
    .timeline-header {
        flex-direction: column;
    }
    
    .skills-grid {
        grid-template-columns: 1fr;
    }
    
    .awards-grid {
        grid-template-columns: 1fr;
    }
}

/* Print Styles */
@media print {
    .nav, .hero-scroll, .theme-toggle {
        display: none;
    }
    
    .hero {
        min-height: auto;
        padding: var(--space-lg);
    }
    
    .section {
        padding: var(--space-lg) 0;
    }
    
    .category-content {
        max-height: none;
    }
}