/* ================================================
   Liu Lab Website - Clean Academic Style
   Inspired by synthneuro.org
   ================================================ */

/* CSS Variables */
:root {
    --color-text: #1a1a1a;
    --color-text-secondary: #4a4a4a;
    --color-text-muted: #6b6b6b;
    --color-bg: #ffffff;
    --color-bg-alt: #f7f7f7;
    --color-border: #e0e0e0;
    --color-accent: #2c5282;
    --color-accent-hover: #1a365d;

    --font-sans: 'Source Sans 3', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-serif: 'Source Serif 4', Georgia, 'Times New Roman', serif;

    --max-width: 900px;
    --max-width-wide: 1100px;

    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    --spacing-3xl: 6rem;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    font-size: 1rem;
    line-height: 1.7;
    color: var(--color-text);
    background-color: var(--color-bg);
    -webkit-font-smoothing: antialiased;
}

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

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

a:hover {
    text-decoration: underline;
}

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

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

h2 {
    font-size: 2rem;
    margin-bottom: var(--spacing-lg);
}

h3 {
    font-size: 1.35rem;
    margin-bottom: var(--spacing-sm);
}

h4 {
    font-size: 1.1rem;
    margin-bottom: var(--spacing-xs);
}

p {
    margin-bottom: var(--spacing-sm);
}

p:last-child {
    margin-bottom: 0;
}

/* Button */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    background-color: var(--color-text);
    color: var(--color-bg);
    font-family: var(--font-sans);
    font-size: 0.9375rem;
    font-weight: 500;
    text-decoration: none;
    border: none;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

.btn:hover {
    background-color: var(--color-text-secondary);
    text-decoration: none;
}

/* Header */
.site-header {
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-container {
    max-width: var(--max-width-wide);
    margin: 0 auto;
    padding: var(--spacing-sm) var(--spacing-md);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.site-logo {
    text-decoration: none;
    display: flex;
    flex-direction: column;
}

.logo-main {
    font-family: var(--font-serif);
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-text);
    line-height: 1.1;
}

.logo-sub {
    font-size: 0.8125rem;
    color: var(--color-text-muted);
}

.main-nav {
    display: flex;
    align-items: center;
}

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

.nav-menu a {
    font-size: 0.9375rem;
    color: var(--color-text);
    padding: var(--spacing-xs) 0;
}

.nav-menu a:hover {
    color: var(--color-accent);
    text-decoration: none;
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 4px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.nav-toggle span {
    width: 22px;
    height: 2px;
    background-color: var(--color-text);
}

/* Hero */
.hero {
    background: var(--color-bg);
}

.hero-image {
    width: 100%;
    max-height: 400px;
    overflow: hidden;
}

.hero-image img {
    width: 100%;
    height: 400px;
    object-fit: cover;
}

.hero-content {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: var(--spacing-xl) var(--spacing-md);
}

.hero-text {
    font-family: var(--font-serif);
    font-size: 1.25rem;
    line-height: 1.7;
    color: var(--color-text);
    margin: 0;
}

/* Sections */
.section {
    padding: var(--spacing-3xl) 0;
}

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

/* About */
.about-content {
    font-size: 1.0625rem;
    color: var(--color-text-secondary);
}

.about-content p {
    margin-bottom: var(--spacing-md);
}

/* Research Grid */
.research-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-xl);
}

.research-card {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
}

.card-image {
    width: 100%;
    height: 200px;
    overflow: hidden;
    background: #000;
}

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

.card-content {
    padding: var(--spacing-md);
}

.card-content h3 {
    color: var(--color-text);
}

.card-content p {
    font-size: 0.9375rem;
    color: var(--color-text-secondary);
    line-height: 1.6;
}

/* People Section */
.pi-section {
    margin-bottom: var(--spacing-xl);
}

.pi-card {
    padding: var(--spacing-lg);
    background: var(--color-bg-alt);
    border-left: 4px solid var(--color-accent);
}

.pi-info h3 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-xs);
}

.pi-title {
    font-size: 1rem;
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-md);
}

.pi-bio {
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-md);
}

.pi-contact {
    font-size: 0.9375rem;
}

.pi-contact .separator {
    margin: 0 var(--spacing-sm);
    color: var(--color-border);
}

.team-section {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.team-group h4 {
    font-family: var(--font-sans);
    font-size: 0.8125rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-text-muted);
    padding-bottom: var(--spacing-xs);
    border-bottom: 1px solid var(--color-border);
    margin-bottom: var(--spacing-sm);
}

.team-list {
    list-style: none;
}

.team-list li {
    margin-bottom: var(--spacing-sm);
}

.team-list li strong {
    display: block;
    font-weight: 600;
    color: var(--color-text);
}

.team-list li span {
    font-size: 0.875rem;
    color: var(--color-text-muted);
}

.team-list.inline {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-md);
}

.team-list.inline li {
    margin-bottom: 0;
}

.team-photo {
    max-width: 700px;
    margin: 0 auto;
}

.team-photo img {
    width: 100%;
    border: 1px solid var(--color-border);
}

.photo-caption {
    font-size: 0.875rem;
    color: var(--color-text-muted);
    text-align: center;
    margin-top: var(--spacing-sm);
    font-style: italic;
}

/* Publications */
.publications-list {
    margin-bottom: var(--spacing-lg);
}

.publication {
    display: flex;
    gap: var(--spacing-md);
    padding: var(--spacing-md) 0;
    border-bottom: 1px solid var(--color-border);
}

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

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

.pub-year {
    font-family: var(--font-serif);
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--color-accent);
    min-width: 60px;
    flex-shrink: 0;
}

.pub-info h4 {
    font-family: var(--font-sans);
    font-size: 1rem;
    font-weight: 500;
    line-height: 1.5;
    margin-bottom: var(--spacing-xs);
}

.pub-info h4 a {
    color: var(--color-text);
    text-decoration: none;
}

.pub-info h4 a:hover {
    color: var(--color-accent);
    text-decoration: underline;
}

.pub-info .authors {
    font-size: 0.9375rem;
    color: var(--color-text-secondary);
    margin-bottom: 0.25rem;
}

.pub-info .journal {
    font-size: 0.875rem;
    color: var(--color-text-muted);
    font-style: italic;
}

.publications-link {
    margin-top: var(--spacing-md);
}

.publications-link a {
    font-weight: 500;
}

/* Join Section */
.join-content > p {
    font-size: 1.0625rem;
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-lg);
}

.positions-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

.position-card {
    padding: var(--spacing-md);
    background: var(--color-bg-alt);
    border: 1px solid var(--color-border);
}

.position-card h4 {
    font-family: var(--font-serif);
    color: var(--color-text);
    margin-bottom: var(--spacing-xs);
}

.position-card p {
    font-size: 0.9375rem;
    color: var(--color-text-secondary);
}

.join-cta {
    text-align: center;
    margin-top: var(--spacing-lg);
}

/* Contact Section */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1.5fr;
    gap: var(--spacing-xl);
}

.contact-info {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

.contact-block h4 {
    font-family: var(--font-sans);
    font-size: 0.8125rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-xs);
}

.contact-block p {
    color: var(--color-text-secondary);
    line-height: 1.6;
}

.contact-map {
    border: 1px solid var(--color-border);
}

.contact-map iframe {
    display: block;
}

/* Footer */
.site-footer {
    background: var(--color-text);
    color: var(--color-bg);
    padding: var(--spacing-xl) 0 var(--spacing-lg);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    padding-bottom: var(--spacing-lg);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-logo {
    font-family: var(--font-serif);
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
}

.footer-info p {
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.7);
    line-height: 1.6;
}

.footer-links {
    display: flex;
    gap: var(--spacing-lg);
}

.footer-links a {
    font-size: 0.875rem;
    color: rgba(255, 255, 255, 0.7);
}

.footer-links a:hover {
    color: var(--color-bg);
}

.footer-bottom {
    padding-top: var(--spacing-lg);
    text-align: center;
}

.footer-bottom p {
    font-size: 0.8125rem;
    color: rgba(255, 255, 255, 0.5);
}

/* Responsive */
@media (max-width: 900px) {
    .research-grid {
        grid-template-columns: 1fr;
    }

    .team-section {
        grid-template-columns: 1fr;
    }

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

    .positions-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    :root {
        --spacing-3xl: 4rem;
    }

    .nav-toggle {
        display: flex;
    }

    .nav-menu {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--color-bg);
        flex-direction: column;
        padding: var(--spacing-sm) var(--spacing-md);
        gap: 0;
        border-bottom: 1px solid var(--color-border);
        display: none;
    }

    .nav-menu.active {
        display: flex;
    }

    .nav-menu li {
        border-bottom: 1px solid var(--color-border);
    }

    .nav-menu li:last-child {
        border-bottom: none;
    }

    .nav-menu a {
        display: block;
        padding: var(--spacing-sm) 0;
    }

    .hero-image img {
        height: 250px;
    }

    .hero-text {
        font-size: 1.125rem;
    }

    h2 {
        font-size: 1.5rem;
    }

    .footer-content {
        flex-direction: column;
        gap: var(--spacing-lg);
    }

    .footer-links {
        flex-direction: column;
        gap: var(--spacing-sm);
    }

    .publication {
        flex-direction: column;
        gap: var(--spacing-xs);
    }

    .pub-year {
        font-size: 1rem;
    }
}

@media (max-width: 480px) {
    .header-container {
        padding: var(--spacing-sm);
    }

    .container {
        padding: 0 var(--spacing-sm);
    }

    .team-list.inline {
        flex-direction: column;
        gap: var(--spacing-sm);
    }
}