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

:root {
    --primary-color: #1a365d;
    --secondary-color: #2c5282;
    --accent-color: #3182ce;
    --text-color: #2d3748;
    --light-bg: #f7fafc;
    --white: #ffffff;
    --border-color: #e2e8f0;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--light-bg);
}

a {
    color: var(--accent-color);
    text-decoration: none;
    transition: color 0.3s ease;
}

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

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Navigation */
.navbar {
    background-color: var(--primary-color);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand {
    color: var(--white);
    font-size: 1.5rem;
    font-weight: bold;
}

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

.nav-menu a {
    color: rgba(255, 255, 255, 0.9);
    font-weight: 500;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    transition: background-color 0.3s ease;
}

.nav-menu a:hover,
.nav-menu a.active {
    background-color: rgba(255, 255, 255, 0.1);
    color: var(--white);
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--secondary-color) 100%);
    color: var(--white);
    padding: 4rem 0;
}

.hero-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

.profile-section {
    display: flex;
    align-items: center;
    gap: 3rem;
}

.profile-image {
    width: 180px;
    height: 180px;
    border-radius: 50%;
    overflow: hidden;
    border: 4px solid rgba(255, 255, 255, 0.9);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

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

.profile-info h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

.profile-info .title {
    font-size: 1.3rem;
    opacity: 0.9;
    margin-bottom: 0.5rem;
}

.profile-info .affiliation {
    opacity: 0.8;
    margin-bottom: 1rem;
}

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

.social-links a {
    color: var(--white);
    font-size: 1.5rem;
    transition: transform 0.3s ease, opacity 0.3s ease;
}

.social-links a:hover {
    transform: translateY(-2px);
    opacity: 0.8;
}

/* Main Content Sections */
main.container {
    padding-top: 3rem;
    padding-bottom: 3rem;
}

section {
    background: var(--white);
    padding: 2rem;
    margin-bottom: 2rem;
    border-radius: 8px;
    box-shadow: var(--shadow);
}

section h2 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--accent-color);
}

/* About Section */
.about-section p {
    margin-bottom: 1rem;
}

/* Timeline (Education) */
.timeline {
    position: relative;
    padding-left: 2rem;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 2px;
    background: var(--accent-color);
}

.timeline-item {
    position: relative;
    margin-bottom: 1.5rem;
    padding-left: 1.5rem;
}

.timeline-item::before {
    content: '';
    position: absolute;
    left: -2rem;
    top: 0.5rem;
    width: 12px;
    height: 12px;
    background: var(--accent-color);
    border-radius: 50%;
    transform: translateX(-5px);
}

.timeline-date {
    color: var(--accent-color);
    font-weight: bold;
    margin-bottom: 0.25rem;
}

.timeline-content h3 {
    color: var(--primary-color);
    font-size: 1.1rem;
}

.timeline-content p {
    color: var(--text-color);
    opacity: 0.8;
}

/* Experience Grid */
.experience-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
}

.experience-card {
    padding: 1.5rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    transition: box-shadow 0.3s ease;
}

.experience-card:hover {
    box-shadow: var(--shadow);
}

.experience-card h3 {
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.experience-card .org {
    color: var(--accent-color);
    font-weight: 500;
}

.experience-card .period {
    color: var(--text-color);
    opacity: 0.7;
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

.experience-card .desc {
    font-size: 0.9rem;
}

/* Awards List */
.awards-list {
    list-style: none;
}

.awards-list li {
    padding: 0.75rem 0;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 1rem;
}

.awards-list li:last-child {
    border-bottom: none;
}

.awards-list i {
    color: var(--accent-color);
    font-size: 1.2rem;
}

/* Service List */
.service-list {
    list-style: none;
}

.service-list li {
    padding: 0.5rem 0;
    padding-left: 1.5rem;
    position: relative;
}

.service-list li::before {
    content: '\2022';
    color: var(--accent-color);
    position: absolute;
    left: 0;
    font-weight: bold;
}

/* News List */
.news-list {
    list-style: none;
}

.news-list li {
    display: flex;
    gap: 1.5rem;
    padding: 1rem 0;
    border-bottom: 1px solid var(--border-color);
}

.news-list li:last-child {
    border-bottom: none;
}

.news-list .date {
    color: var(--accent-color);
    font-weight: bold;
    min-width: 60px;
}

/* Publications Page */
.publication-list {
    list-style: none;
}

.publication-item {
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

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

.publication-item h3 {
    color: var(--primary-color);
    font-size: 1.1rem;
    margin-bottom: 0.5rem;
}

.publication-item .authors {
    color: var(--text-color);
    margin-bottom: 0.25rem;
}

.publication-item .venue {
    color: var(--accent-color);
    font-style: italic;
}

.publication-item .year {
    color: var(--text-color);
    opacity: 0.7;
}

.publication-item .links {
    margin-top: 0.5rem;
}

.publication-item .links a {
    margin-right: 1rem;
    font-size: 0.9rem;
}

/* Publication Filter Tabs */
.filter-tabs {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    padding: 1rem;
    background-color: var(--white);
    border-radius: 8px;
    box-shadow: var(--shadow);
}

.filter-btn {
    padding: 0.5rem 1rem;
    background-color: var(--white);
    color: var(--text-color);
    border: 2px solid var(--border-color);
    border-radius: 20px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 500;
    transition: all 0.3s ease;
}

.filter-btn:hover {
    background-color: var(--light-bg);
    border-color: var(--accent-color);
}

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

.publication-item.hidden {
    display: none;
}

.year-heading.hidden {
    display: none;
}

/* Research Areas */
.research-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
}

.research-card {
    padding: 1.5rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

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

.research-card h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.research-card i {
    color: var(--accent-color);
}

/* Projects Section */
.project-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1.5rem;
}

.project-card {
    padding: 1.5rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    background: var(--light-bg);
}

.project-card h3 {
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.project-card .partners {
    color: var(--accent-color);
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

/* Contact Section */
.contact-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
}

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

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

.contact-item h3 {
    color: var(--primary-color);
    margin-bottom: 0.25rem;
}

/* Footer */
.footer {
    background-color: var(--primary-color);
    color: var(--white);
    padding: 2rem 0;
    text-align: center;
}

.footer p {
    opacity: 0.9;
    margin-bottom: 0.5rem;
}

/* Teaching Page */
.course-list {
    list-style: none;
}

.course-item {
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.course-item:last-child {
    border-bottom: none;
}

.course-item h3 {
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.course-item .code {
    color: var(--accent-color);
    font-weight: 500;
}

/* Year Filter */
.year-filter {
    margin-bottom: 1.5rem;
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.year-filter button {
    padding: 0.5rem 1rem;
    border: 1px solid var(--accent-color);
    background: var(--white);
    color: var(--accent-color);
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.year-filter button:hover,
.year-filter button.active {
    background: var(--accent-color);
    color: var(--white);
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        display: none;
    }

    .profile-section {
        flex-direction: column;
        text-align: center;
    }

    .profile-info h1 {
        font-size: 1.8rem;
    }

    .social-links {
        justify-content: center;
    }

    .experience-grid,
    .research-grid,
    .project-grid,
    .contact-grid {
        grid-template-columns: 1fr;
    }

    .news-list li {
        flex-direction: column;
        gap: 0.5rem;
    }
}