/* css/style.css */

/* ===========================
   CSS Variables
   =========================== */
:root {
    --primary-color: #2563eb;
    --secondary-color: #1e40af;
    --text-dark: #1f2937;
    --text-light: #6b7280;
    --bg-light: #f9fafb;
    --bg-white: #ffffff;
    --border-color: #e5e7eb;
    --accent-color: #10b981;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s ease;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-dark);
    background-color: var(--bg-white);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

/* ===========================
   Navigation
   =========================== */
nav {
    position: fixed;
    top: 0;
    width: 100%;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow);
    z-index: 1000;
    transition: var(--transition);
}

nav.scrolled {
    box-shadow: var(--shadow-lg);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary-color);
    text-decoration: none;
    transition: var(--transition);
}

.nav-logo:hover {
    opacity: 0.8;
}

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

.nav-menu a {
    color: var(--text-dark);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

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

.nav-menu a.active::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 100%;
    height: 2px;
    background: var(--primary-color);
}

.nav-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-dark);
}

/* ===========================
   Hero Section
   =========================== */
.hero {
    margin-top: 70px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 5rem 2rem;
    text-align: center;
}

.hero-container {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2rem;
}

.hero-image {
    width: 180px;
    height: 180px;
    border-radius: 50%;
    border: 5px solid rgba(255, 255, 255, 0.3);
    object-fit: cover;
    box-shadow: var(--shadow-lg);
    transition: transform 0.3s ease;
}

.hero-image:hover {
    transform: scale(1.05);
}

.hero-content h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
}

.hero-subtitle {
    font-size: 1.25rem;
    opacity: 0.95;
    margin-bottom: 1rem;
}

.hero-description {
    max-width: 700px;
    font-size: 1.1rem;
    line-height: 1.8;
    opacity: 0.9;
    margin-bottom: 1.5rem;
}

.research-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    justify-content: center;
    margin-bottom: 2rem;
}

.tag {
    background: rgba(255, 255, 255, 0.2);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.9rem;
    backdrop-filter: blur(10px);
    transition: var(--transition);
}

.tag:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: translateY(-2px);
}

.social-links {
    display: flex;
    gap: 1rem;
    justify-content: center;
    flex-wrap: wrap;
}

.social-link {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    background: rgba(255, 255, 255, 0.2);
    color: white;
    text-decoration: none;
    border-radius: 8px;
    transition: var(--transition);
    backdrop-filter: blur(10px);
}

.social-link:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: translateY(-2px);
}

/* ===========================
   Section Styles
   =========================== */
section {
    padding: 4rem 2rem;
}

.page-section {
    max-width: 1200px;
    margin: 90px auto 0;
    padding: 4rem 2rem;
}

.section-title {
    font-size: 2rem;
    margin-bottom: 2rem;
    color: var(--text-dark);
    position: relative;
    padding-bottom: 0.5rem;
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 60px;
    height: 4px;
    background: var(--primary-color);
    border-radius: 2px;
}

/* ===========================
   Overview Cards (Home)
   =========================== */
.overview-section {
    background: var(--bg-light);
}

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

.overview-card {
    background: var(--bg-white);
    padding: 2rem;
    border-radius: 8px;
    text-align: center;
    box-shadow: var(--shadow);
    transition: var(--transition);
}

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

.overview-icon {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.overview-card h3 {
    color: var(--text-dark);
    margin-bottom: 1rem;
}

.overview-card p {
    color: var(--text-light);
    margin-bottom: 1rem;
}

.card-link {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition);
}

.card-link:hover {
    opacity: 0.8;
}

/* ===========================
   News Section
   =========================== */
.news-section {
    background: var(--bg-white);
}

.news-list {
    max-width: 800px;
}

.news-item {
    display: flex;
    gap: 2rem;
    padding: 1.5rem;
    background: var(--bg-light);
    border-radius: 8px;
    margin-bottom: 1rem;
    border-left: 4px solid var(--primary-color);
    transition: var(--transition);
}

.news-item:hover {
    transform: translateX(5px);
    box-shadow: var(--shadow);
}

.news-date {
    font-weight: 600;
    color: var(--primary-color);
    min-width: 100px;
}

.news-item p {
    color: var(--text-dark);
}

/* ===========================
   About Section
   =========================== */
.about-content {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 3rem;
}

.about-text p {
    margin-bottom: 1rem;
    color: var(--text-light);
    text-align: justify;
}

.skills-container {
    background: var(--bg-light);
    padding: 1.5rem;
    border-radius: 8px;
}

.skills-container h3 {
    margin-bottom: 1rem;
    color: var(--text-dark);
}

.skill-category {
    margin-bottom: 1.5rem;
}

.skill-category h4 {
    font-size: 0.9rem;
    color: var(--text-light);
    margin-bottom: 0.5rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.skill-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.skill-tag {
    background: var(--bg-white);
    padding: 0.4rem 0.8rem;
    border-radius: 6px;
    font-size: 0.85rem;
    color: var(--text-dark);
    border: 1px solid var(--border-color);
    transition: var(--transition);
}

.skill-tag:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

/* ===========================
   Publications Section
   =========================== */
.publication {
    background: var(--bg-light);
    padding: 1.5rem;
    border-radius: 8px;
    margin-bottom: 1.5rem;
    border-left: 4px solid var(--primary-color);
    transition: var(--transition);
}

.publication:hover {
    transform: translateX(5px);
    box-shadow: var(--shadow);
}

.publication.first-author {
    border-left-color: var(--accent-color);
}

.pub-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-dark);
    margin-bottom: 0.5rem;
}

.pub-authors {
    color: var(--text-light);
    margin-bottom: 0.5rem;
    font-style: italic;
}

.pub-venue {
    color: var(--text-dark);
    font-weight: 500;
    margin-bottom: 0.5rem;
}

.pub-status {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 600;
    margin-bottom: 0.75rem;
}

.pub-status.published {
    background: #dcfce7;
    color: #166534;
}

.pub-status.review {
    background: #fef3c7;
    color: #92400e;
}

.pub-links {
    display: flex;
    gap: 0.75rem;
    flex-wrap: wrap;
}

.pub-link {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    padding: 0.4rem 0.8rem;
    background: var(--primary-color);
    color: white;
    text-decoration: none;
    border-radius: 6px;
    font-size: 0.85rem;
    transition: var(--transition);
}

.pub-link:hover {
    background: var(--secondary-color);
}

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

.project-card {
    background: var(--bg-light);
    padding: 2rem;
    border-radius: 8px;
    border-top: 4px solid var(--primary-color);
    transition: var(--transition);
}

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

.project-card h3 {
    color: var(--text-dark);
    margin-bottom: 1rem;
}

.project-card p {
    color: var(--text-light);
    margin-bottom: 1rem;
}

.project-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 1rem;
}

.project-tag {
    background: var(--bg-white);
    padding: 0.3rem 0.6rem;
    border-radius: 4px;
    font-size: 0.8rem;
    color: var(--primary-color);
    border: 1px solid var(--primary-color);
}

/* ===========================
   Conference Section
   =========================== */
.conference-list {
    display: grid;
    gap: 1.5rem;
}

.conference-item {
    background: var(--bg-light);
    padding: 1.5rem;
    border-radius: 8px;
    display: flex;
    gap: 1.5rem;
    align-items: start;
    transition: var(--transition);
}

.conference-item:hover {
    box-shadow: var(--shadow);
}

.conference-year {
    font-size: 2rem;
    font-weight: 700;
    color: var(--primary-color);
    min-width: 80px;
}

.conference-details h3 {
    margin-bottom: 0.5rem;
    color: var(--text-dark);
}

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

.award-badge {
    display: inline-block;
    padding: 0.3rem 0.8rem;
    background: #fef3c7;
    color: #92400e;
    border-radius: 12px;
    font-size: 0.85rem;
    font-weight: 600;
    margin-top: 0.5rem;
}

/* ===========================
   Education Section
   =========================== */
.education-timeline {
    position: relative;
    padding-left: 2rem;
}

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

.education-item {
    position: relative;
    margin-bottom: 2rem;
    padding-left: 2rem;
    transition: var(--transition);
}

.education-item:hover {
    transform: translateX(5px);
}

.education-item::before {
    content: '';
    position: absolute;
    left: -2rem;
    top: 0;
    width: 12px;
    height: 12px;
    background: var(--primary-color);
    border-radius: 50%;
    border: 3px solid var(--bg-white);
    box-shadow: 0 0 0 3px var(--border-color);
}

.education-item h3 {
    color: var(--text-dark);
    margin-bottom: 0.25rem;
}

.education-item .institution {
    color: var(--primary-color);
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.education-item .period {
    color: var(--text-light);
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
}

.education-item p {
    color: var(--text-light);
    margin-bottom: 0.25rem;
}

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

.contact-card {
    background: var(--bg-light);
    padding: 2rem;
    border-radius: 8px;
    text-align: center;
    transition: var(--transition);
}

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

.contact-icon {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.contact-card h3 {
    margin-bottom: 0.5rem;
    color: var(--text-dark);
}

.contact-card p {
    color: var(--text-light);
}

.contact-card a {
    color: var(--primary-color);
    text-decoration: none;
    word-break: break-all;
    transition: var(--transition);
}

.contact-card a:hover {
    text-decoration: underline;
}

/* ===========================
   Footer
   =========================== */
footer {
    background: var(--text-dark);
    color: white;
    text-align: center;
    padding: 2rem;
    margin-top: 4rem;
}

.footer-content p {
    opacity: 0.8;
    margin-bottom: 0.5rem;
}

/* ===========================
   Scroll to Top Button
   =========================== */
.scroll-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 50px;
    height: 50px;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 50%;
    font-size: 1.5rem;
    cursor: pointer;
    opacity: 0;
    transition: var(--transition);
    z-index: 999;
    box-shadow: var(--shadow-lg);
}

.scroll-top.visible {
    opacity: 1;
}

.scroll-top:hover {
    transform: translateY(-5px);
    background: var(--secondary-color);
}

/* ===========================
   Responsive Design
   =========================== */
@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background: var(--bg-white);
        width: 100%;
        text-align: center;
        transition: 0.3s;
        box-shadow: var(--shadow-lg);
        padding: 2rem 0;
        gap: 0;
    }

    .nav-menu li {
        padding: 1rem 0;
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-toggle {
        display: block;
    }

    .hero-content h1 {
        font-size: 2rem;
    }

    .about-content {
        grid-template-columns: 1fr;
    }

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

    .conference-item {
        flex-direction: column;
    }

    .social-links {
        flex-direction: column;
        width: 100%;
    }

    .social-link {
        width: 100%;
        justify-content: center;
    }
}