/* Custom CSS for Dr. Xingmeng Zhao Portfolio */

:root {
    --primary-color: #1A1A1A;
    --secondary-color: #F8F8F8;
    --accent-color: #666666;
    --text-color: #333333;
    --highlight-color: #000000;
    --white: #ffffff;
    
    --font-serif: 'Playfair Display', serif;
    --font-sans: 'Inter', sans-serif;
    
    --section-padding: 100px 0;
    --transition: all 0.3s ease;
}

/* Global Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    font-weight: 400;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--white);
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-serif);
    font-weight: 600;
    line-height: 1.2;
    color: var(--primary-color);
}

.section-title {
    font-size: 3rem;
    font-weight: 600;
    margin-bottom: 2rem;
    position: relative;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 2px;
    background-color: var(--primary-color);
}

/* Utility Classes */
.section-padding {
    padding: var(--section-padding);
}

.fade-in {
    opacity: 0;
    transform: translateY(30px);
    animation: fadeInUp 1s ease forwards;
}

@keyframes fadeInUp {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Navigation */
.navbar {
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    transition: var(--transition);
    padding: 1rem 0;
}

.navbar.scrolled {
    box-shadow: 0 2px 20px rgba(0, 0, 0, 0.1);
}

.navbar-brand {
    font-family: var(--font-serif);
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--primary-color) !important;
    text-decoration: none;
}

.navbar-nav .nav-link {
    font-family: var(--font-sans);
    font-weight: 500;
    color: var(--text-color) !important;
    padding: 0.5rem 1rem !important;
    transition: var(--transition);
    position: relative;
}

.navbar-nav .nav-link:hover {
    color: var(--primary-color) !important;
}

.navbar-nav .nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 0;
    height: 2px;
    background-color: var(--primary-color);
    transition: var(--transition);
}

.navbar-nav .nav-link:hover::after {
    width: 80%;
}

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

.hero-content {
    text-align: center;
}

.hero-title {
    font-size: 4.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.hero-subtitle {
    font-size: 1.5rem;
    font-weight: 400;
    color: var(--accent-color);
    margin-bottom: 2rem;
}

.hero-description {
    font-size: 1.2rem;
    line-height: 1.8;
    color: var(--text-color);
    max-width: 800px;
    margin: 0 auto;
}

.hero-links .btn {
    padding: 12px 30px;
    font-weight: 500;
    border-radius: 0;
    transition: var(--transition);
    text-decoration: none;
}

.btn-outline-dark {
    border: 2px solid var(--primary-color);
    color: var(--primary-color);
}

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

.btn-dark {
    background-color: var(--primary-color);
    border: 2px solid var(--primary-color);
    color: var(--white);
}

.btn-dark:hover {
    background-color: transparent;
    color: var(--primary-color);
}

.social-links a {
    display: inline-block;
    width: 50px;
    height: 50px;
    line-height: 50px;
    text-align: center;
    color: var(--accent-color);
    font-size: 1.2rem;
    transition: var(--transition);
    margin: 0 10px;
}

.social-links a:hover {
    color: var(--primary-color);
    transform: translateY(-3px);
}

/* Section Styles */
.bg-light {
    background-color: var(--secondary-color) !important;
}

.section-header {
    margin-bottom: 4rem;
}

/* Research Areas */
.research-areas {
    max-width: 800px;
    margin: 0 auto;
}

.research-category {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.research-description {
    font-size: 1.1rem;
    line-height: 1.8;
    color: var(--text-color);
}

/* Education Timeline */
.education-timeline {
    position: relative;
}

.education-item {
    position: relative;
    padding: 2rem 0;
    border-bottom: 1px solid #eee;
}

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

.education-year {
    font-weight: 600;
    color: var(--accent-color);
    font-size: 0.95rem;
}

.education-degree {
    font-size: 1.4rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.education-school {
    font-size: 1.1rem;
    font-weight: 500;
    color: var(--text-color);
    margin-bottom: 1rem;
}

.education-details p {
    margin-bottom: 0.5rem;
    color: var(--text-color);
}

/* Experience Timeline */
.experience-timeline {
    position: relative;
}

.experience-item {
    position: relative;
    padding: 2rem 0;
    border-bottom: 1px solid #eee;
}

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

.experience-date {
    font-weight: 600;
    color: var(--accent-color);
    font-size: 0.95rem;
}

.experience-title {
    font-size: 1.4rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.experience-company {
    font-size: 1.1rem;
    font-weight: 500;
    color: var(--text-color);
    margin-bottom: 1rem;
}

.experience-details {
    list-style: none;
    padding: 0;
}

.experience-details li {
    position: relative;
    padding-left: 1.5rem;
    margin-bottom: 0.75rem;
    color: var(--text-color);
    line-height: 1.6;
}

.experience-details li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: bold;
}

/* Publications */
.publication-category {
    margin-bottom: 3rem;
}

.publication-category-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 2rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--primary-color);
}

.publication-item {
    padding: 1.5rem 0;
    border-bottom: 1px solid #eee;
}

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

.publication-title {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
    line-height: 1.4;
}

.publication-authors {
    font-weight: 500;
    color: var(--text-color);
    margin-bottom: 0.5rem;
}

.publication-venue {
    font-style: italic;
    color: var(--accent-color);
    margin-bottom: 0.5rem;
}

.publication-details {
    font-size: 0.9rem;
    color: var(--accent-color);
}

/* Teaching */
.teaching-timeline {
    position: relative;
}

.teaching-item {
    position: relative;
    padding: 2rem 0;
    border-bottom: 1px solid #eee;
}

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

.teaching-semester {
    font-weight: 600;
    color: var(--accent-color);
    font-size: 0.95rem;
}

.teaching-course {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.teaching-role {
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-color);
    margin-bottom: 1rem;
}

.teaching-details p {
    margin-bottom: 0.5rem;
    color: var(--text-color);
}

/* Awards */
.awards-grid {
    margin-top: 2rem;
}

.award-item {
    background: var(--white);
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.08);
    transition: var(--transition);
    height: 100%;
}

.award-item:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.15);
}

.award-date {
    font-weight: 600;
    color: var(--accent-color);
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

.award-title {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.award-organization {
    color: var(--text-color);
    font-size: 0.95rem;
}

/* Footer */
.footer-section {
    background-color: var(--primary-color);
    color: var(--white);
    padding: 4rem 0 2rem;
}

.footer-content {
    text-align: center;
}

.footer-title {
    font-size: 2.5rem;
    font-weight: 600;
    color: var(--white);
    margin-bottom: 1rem;
}

.footer-description {
    font-size: 1.1rem;
    color: rgba(255, 255, 255, 0.8);
    max-width: 600px;
    margin: 0 auto;
}

.contact-link {
    color: var(--white);
    text-decoration: none;
    font-size: 1.1rem;
    font-weight: 500;
    transition: var(--transition);
}

.contact-link:hover {
    color: rgba(255, 255, 255, 0.8);
}

.contact-link i {
    margin-right: 0.5rem;
}

.footer-location {
    color: rgba(255, 255, 255, 0.8);
    font-size: 1rem;
}

.footer-location i {
    margin-right: 0.5rem;
}

.footer-social {
    margin-top: 2rem;
}

.social-link {
    display: inline-block;
    width: 50px;
    height: 50px;
    line-height: 50px;
    text-align: center;
    color: rgba(255, 255, 255, 0.8);
    font-size: 1.2rem;
    transition: var(--transition);
    margin: 0 10px;
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 50%;
}

.social-link:hover {
    color: var(--white);
    border-color: var(--white);
    transform: translateY(-3px);
}

.footer-bottom {
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.2);
}

.footer-copyright {
    color: rgba(255, 255, 255, 0.6);
    font-size: 0.9rem;
    margin: 0;
}

/* Responsive Design */
@media (max-width: 992px) {
    .hero-title {
        font-size: 3.5rem;
    }
    
    .hero-subtitle {
        font-size: 1.3rem;
    }
    
    .section-title {
        font-size: 2.5rem;
    }
}

@media (max-width: 768px) {
    .hero-title {
        font-size: 2.8rem;
    }
    
    .hero-subtitle {
        font-size: 1.1rem;
    }
    
    .hero-description {
        font-size: 1rem;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .section-padding {
        padding: 60px 0;
    }
    
    .education-item,
    .experience-item,
    .teaching-item {
        padding: 1.5rem 0;
    }
    
    .award-item {
        margin-bottom: 1.5rem;
    }
}

@media (max-width: 576px) {
    .hero-title {
        font-size: 2.2rem;
    }
    
    .hero-links .btn {
        display: block;
        margin: 0.5rem 0;
        width: 100%;
    }
    
    .navbar-brand {
        font-size: 1.2rem;
    }
    
    .footer-title {
        font-size: 2rem;
    }
}

/* Animations */
.section-padding {
    opacity: 0;
    transform: translateY(50px);
    transition: all 0.6s ease;
}

.section-padding.animate {
    opacity: 1;
    transform: translateY(0);
}

/* Smooth transitions for all interactive elements */
a, button, .btn {
    transition: var(--transition);
}

/* About Section Enhancements */
.about-content {
    max-width: 100%;
}

.about-text {
    font-size: 1.1rem;
    line-height: 1.8;
    color: var(--text-color);
    margin-bottom: 1.5rem;
}

.about-text.lead {
    font-size: 1.3rem;
    font-weight: 500;
    color: var(--primary-color);
}

.research-focus-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

/* Research Areas Grid */
.research-areas-grid {
    margin-top: 4rem;
}

.research-areas-title {
    font-size: 2rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.research-areas-subtitle {
    font-size: 1.1rem;
    color: var(--accent-color);
    margin-bottom: 3rem;
}

.research-card-link {
    text-decoration: none;
    color: inherit;
}

.research-card {
    background: var(--white);
    padding: 2.5rem 1.5rem;
    border-radius: 12px;
    box-shadow: 0 5px 20px rgba(0, 0, 0, 0.08);
    transition: var(--transition);
    height: 100%;
    text-align: center;
    border: 1px solid transparent;
}

.research-card:hover {
    transform: translateY(-8px);
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.15);
    border-color: var(--primary-color);
}

.research-card-icon {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.research-card-title {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.research-card-description {
    color: var(--text-color);
    line-height: 1.6;
    margin: 0;
}

/* Research Detail Sections */
.research-detail-header {
    margin-bottom: 3rem;
}

.research-detail-description {
    font-size: 1.2rem;
    line-height: 1.7;
    color: var(--text-color);
    max-width: 800px;
    margin: 0 auto;
}

.research-projects {
    margin-top: 2rem;
}

.research-project {
    background: var(--white);
    padding: 3rem 2rem;
    border-radius: 12px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.06);
    transition: var(--transition);
}

.research-project:hover {
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.12);
    transform: translateY(-3px);
}

.project-title {
    font-size: 1.6rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.project-description {
    font-size: 1.1rem;
    line-height: 1.7;
    color: var(--text-color);
    margin-bottom: 1.5rem;
}

.project-icon {
    text-align: center;
    font-size: 4rem;
    color: var(--accent-color);
    opacity: 0.3;
}

.project-publications h5 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.75rem;
}

.publication-links {
    list-style: none;
    padding: 0;
    margin: 0;
}

.publication-links li {
    margin-bottom: 0.5rem;
}

.publication-links a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    border-bottom: 1px solid transparent;
    transition: var(--transition);
}

.publication-links a:hover {
    border-bottom-color: var(--primary-color);
    color: var(--highlight-color);
}

/* Enhanced Publications Section */
.publication-item {
    background: var(--white);
    padding: 2rem;
    border-radius: 8px;
    margin-bottom: 1.5rem;
    border: 1px solid #eee;
    transition: var(--transition);
}

.publication-item:hover {
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    transform: translateY(-2px);
    border-color: var(--primary-color);
}

.publication-title {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
}

.publication-title a {
    color: var(--primary-color);
    text-decoration: none;
    transition: var(--transition);
}

.publication-title a:hover {
    color: var(--highlight-color);
    text-decoration: underline;
}

.publication-authors {
    font-weight: 500;
    color: var(--text-color);
    margin-bottom: 0.5rem;
}

.publication-venue {
    font-style: italic;
    color: var(--accent-color);
    margin-bottom: 0.5rem;
}

.publication-details {
    font-size: 0.9rem;
    color: var(--accent-color);
}

.publication-links-footer {
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid #eee;
}

.publication-link {
    display: inline-block;
    margin-right: 1rem;
    margin-bottom: 0.5rem;
    padding: 0.4rem 1rem;
    background: var(--secondary-color);
    color: var(--primary-color);
    text-decoration: none;
    border-radius: 20px;
    font-size: 0.9rem;
    font-weight: 500;
    transition: var(--transition);
}

.publication-link:hover {
    background: var(--primary-color);
    color: var(--white);
}

.publication-link i {
    margin-right: 0.5rem;
}

/* Custom scrollbar */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: var(--secondary-color);
}

::-webkit-scrollbar-thumb {
    background: var(--accent-color);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--primary-color);
}

/* 5-Card Layout Support */
.col-xl-2dot4 {
    flex: 0 0 auto;
    width: 20%;
}

@media (max-width: 1199.98px) {
    .col-xl-2dot4 {
        width: 33.333333%;
    }
}

@media (max-width: 767.98px) {
    .col-xl-2dot4 {
        width: 100%;
    }
}

/* Framework Sections */
.research-focus-subtitle {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.75rem;
}

.framework-areas {
    margin-top: 2rem;
}

.framework-item {
    background: var(--secondary-color);
    padding: 1.5rem;
    border-radius: 8px;
    border-left: 4px solid var(--primary-color);
}

.framework-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.75rem;
}

.framework-description {
    color: var(--text-color);
    line-height: 1.6;
    margin: 0;
}

/* Responsive Design for Research Cards */
@media (max-width: 768px) {
    .research-card {
        margin-bottom: 2rem;
    }
    
    .research-project {
        padding: 2rem 1rem;
    }
    
    .project-icon {
        font-size: 3rem;
        margin-bottom: 1rem;
    }
    
    .research-areas-title {
        font-size: 1.7rem;
    }
    
    .framework-item {
        margin-bottom: 1rem;
    }
}