:root {
    --primary-color: #003366;
    --secondary-color: #F4F4F9;
    --accent-color: #B38808;
    --text-color: #333333;
    --text-light: #666666;
    --font-heading: Georgia, 'Times New Roman', serif;
    --font-body: Helvetica, Arial, sans-serif;
    --container-width: 1100px;
}

body {
    font-family: var(--font-body);
    color: var(--text-color);
    line-height: 1.6;
    margin: 0;
    padding: 0;
    background-color: var(--secondary-color);
}

h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-heading);
    color: var(--primary-color);
}

/* i18n support */
body .lang-zh { display: none; }
body.lang-zh-active .lang-zh { display: initial; }
body.lang-zh-active .lang-en { display: none; }

/* In case of block elements */
body div.lang-zh, body p.lang-zh, body h1.lang-zh, body h2.lang-zh, body h3.lang-zh, body li.lang-zh { display: none; }
body.lang-zh-active div.lang-zh, body.lang-zh-active p.lang-zh, body.lang-zh-active h1.lang-zh, body.lang-zh-active h2.lang-zh, body.lang-zh-active h3.lang-zh, body.lang-zh-active li.lang-zh { display: block; }

body.lang-zh-active div.lang-en, body.lang-zh-active p.lang-en, body.lang-zh-active h1.lang-en, body.lang-zh-active h2.lang-en, body.lang-zh-active h3.lang-en, body.lang-zh-active li.lang-en { display: none; }


/* Header & Nav */
header {
    background-color: var(--primary-color);
    color: white;
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

.header-container {
    max-width: var(--container-width);
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 2rem;
}

.logo h1 {
    color: white;
    margin: 0;
    font-size: 1.8rem;
    font-family: var(--font-heading);
    letter-spacing: 1px;
}

.logo p {
    margin: 0;
    font-size: 0.9rem;
    color: var(--accent-color);
    font-weight: bold;
}

nav {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

nav a {
    color: white;
    text-decoration: none;
    font-weight: 500;
    font-size: 1rem;
    transition: color 0.3s;
}

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

#lang-toggle {
    background-color: var(--accent-color);
    color: white;
    border: none;
    padding: 0.4rem 0.8rem;
    border-radius: 4px;
    cursor: pointer;
    font-weight: bold;
    font-size: 0.9rem;
    transition: background-color 0.3s;
}

#lang-toggle:hover {
    background-color: #926f06;
}

/* Layout */
.container {
    max-width: var(--container-width);
    margin: 2rem auto;
    padding: 0 2rem;
    background-color: white;
    box-shadow: 0 0 10px rgba(0,0,0,0.05);
    min-height: 60vh;
}

.section {
    padding: 3rem 0;
    border-bottom: 1px solid #eee;
}
.section:last-child {
    border-bottom: none;
}

.section h2 {
    font-size: 2rem;
    margin-top: 0;
    margin-bottom: 1.5rem;
    border-left: 5px solid var(--accent-color);
    padding-left: 15px;
}

/* Hero Section */
.hero {
    background: linear-gradient(rgba(0, 51, 102, 0.8), rgba(0, 51, 102, 0.8)), url('https://images.unsplash.com/photo-1576086213369-97a306d36557?auto=format&fit=crop&q=80&w=1600') center/cover;
    color: white;
    text-align: center;
    padding: 6rem 2rem;
    margin-bottom: 2rem;
}

.hero h1 {
    color: white;
    font-size: 3rem;
    margin-bottom: 1rem;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.5);
}

.hero p {
    font-size: 1.2rem;
    max-width: 800px;
    margin: 0 auto;
    font-family: var(--font-heading);
    font-style: italic;
    color: #e0e0e0;
}

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

.card {
    background-color: white;
    border: 1px solid #ddd;
    border-top: 4px solid var(--primary-color);
    padding: 1.5rem;
    box-shadow: 0 4px 6px rgba(0,0,0,0.05);
    transition: transform 0.3s, box-shadow 0.3s;
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 15px rgba(0,0,0,0.1);
}

.card h3 {
    margin-top: 0;
    font-size: 1.3rem;
    border-bottom: 1px dashed #ccc;
    padding-bottom: 10px;
}

/* Publications */
.pub-list {
    list-style: none;
    padding: 0;
}
.pub-list li {
    margin-bottom: 1.5rem;
    padding: 1rem;
    background-color: #f9f9f9;
    border-left: 3px solid var(--primary-color);
}
.pub-list strong {
    color: #111;
}
.pub-list em {
    color: var(--primary-color);
}
.pub-actions {
    margin-top: 0.5rem;
}
.pub-actions a, .pub-actions button {
    display: inline-block;
    margin-right: 10px;
    padding: 4px 10px;
    background-color: #e0e0e0;
    color: var(--text-color);
    text-decoration: none;
    font-size: 0.85rem;
    border-radius: 3px;
    border: none;
    cursor: pointer;
}
.pub-actions a:hover, .pub-actions button:hover {
    background-color: var(--primary-color);
    color: white;
}

/* Team */
.team-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 2rem;
}
.team-member {
    text-align: center;
}
.team-member img {
    width: 150px;
    height: 150px;
    border-radius: 50%;
    object-fit: cover;
    border: 3px solid var(--secondary-color);
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}
.team-member h4 {
    margin: 10px 0 5px;
}
.team-member p {
    margin: 0;
    font-size: 0.9rem;
    color: var(--text-light);
}

/* Form */
.contact-form {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    max-width: 600px;
}
.contact-form input, .contact-form textarea {
    padding: 10px;
    border: 1px solid #ccc;
    border-radius: 4px;
    font-family: var(--font-body);
}
.contact-form button {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 1rem;
    align-self: flex-start;
}
.contact-form button:hover {
    background-color: var(--accent-color);
}

/* Chart Container */
.chart-container {
    width: 100%;
    max-width: 800px;
    margin: 2rem auto;
    background: white;
    padding: 1rem;
    border: 1px solid #ddd;
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

/* Footer */
footer {
    background-color: var(--primary-color);
    color: #cfd8dc;
    text-align: center;
    padding: 3rem 1rem;
    margin-top: 4rem;
    border-top: 5px solid var(--accent-color);
}
footer p {
    margin: 0.5rem 0;
    font-size: 0.95rem;
}
footer a {
    color: var(--accent-color);
}