/* ========================================
   RESET & BASE STYLES
   ======================================== */

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

:root {
    /* Colors */
    --primary-color: #2563eb;
    --primary-dark: #1e40af;
    --secondary-color: #64748b;
    --accent-color: #3b82f6;
    --bg-color: #ffffff;
    --bg-secondary: #f8fafc;
    --text-primary: #1e293b;
    --text-secondary: #475569;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    
    /* Typography */
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'Courier New', monospace;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    --spacing-2xl: 4rem;
    
    /* Border radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    color: var(--text-primary);
    line-height: 1.7;
    background-color: var(--bg-color);
    overflow-x: hidden;
}

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

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

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

/* ========================================
   TYPOGRAPHY
   ======================================== */

h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }

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

/* ========================================
   LAYOUT
   ======================================== */

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

.section {
    padding: var(--spacing-2xl) 0;
}

/* ========================================
   NAVIGATION
   ======================================== */

.navbar {
    background: var(--bg-color);
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 1000;
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) var(--spacing-md);
}

.logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    transition: color 0.3s ease;
}

.logo:hover {
    color: var(--primary-color);
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--spacing-lg);
    align-items: center;
}

.nav-link {
    color: var(--text-secondary);
    font-weight: 500;
    font-size: 0.95rem;
    padding: var(--spacing-xs) 0;
    position: relative;
    transition: color 0.3s ease;
}

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

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: width 0.3s ease;
}

.nav-link:hover::after,
.nav-link.active::after {
    width: 100%;
}

.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
    gap: 4px;
}

.bar {
    width: 25px;
    height: 3px;
    background: var(--text-primary);
    border-radius: 3px;
    transition: all 0.3s ease;
}

/* ========================================
   HERO SECTION
   ======================================== */

.hero {
    background: linear-gradient(135deg, #f8fafc 0%, #e0e7ff 100%);
    padding: var(--spacing-2xl) 0;
    min-height: 70vh;
    display: flex;
    align-items: center;
}

.hero-container {
    display: grid;
    grid-template-columns: 1.5fr 1fr;
    gap: var(--spacing-xl);
    align-items: center;
}

.hero-content {
    animation: fadeInUp 0.8s ease;
}

.hero-title {
    font-size: 3rem;
    font-weight: 800;
    margin-bottom: var(--spacing-sm);
    background: linear-gradient(135deg, var(--text-primary) 0%, var(--primary-color) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
}

.hero-location {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
    font-size: 1rem;
}

.hero-links {
    display: flex;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

.hero-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-xs) var(--spacing-md);
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    font-weight: 500;
    font-size: 0.9rem;
    transition: all 0.3s ease;
    box-shadow: var(--shadow-sm);
}

.hero-link:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.hero-image {
    animation: fadeIn 1s ease;
}

.hero-image img {
    width: 100%;
    max-width: 400px;
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-lg);
    margin: 0 auto;
}

/* ========================================
   SECTION TITLES
   ======================================== */

.section-title {
    text-align: center;
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: var(--spacing-xl);
    position: relative;
    padding-bottom: var(--spacing-md);
}

.section-title::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
    border-radius: 2px;
}

/* ========================================
   ABOUT SECTION
   ======================================== */

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

.about-content {
    max-width: 900px;
    margin: 0 auto;
    font-size: 1.1rem;
    line-height: 1.8;
}

.intro-text {
    font-size: 1.2rem;
    color: var(--text-primary);
    margin-bottom: var(--spacing-lg);
}

.about-content strong {
    color: var(--primary-color);
    font-weight: 600;
}

/* ========================================
   RESEARCH INTERESTS
   ======================================== */

.research-section {
    background: var(--bg-secondary);
}

.research-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.research-card {
    background: var(--bg-color);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: all 0.3s ease;
    border: 1px solid var(--border-color);
}

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

.research-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-sm);
}

.research-card h3 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
}

.research-card p {
    font-size: 0.95rem;
    line-height: 1.6;
}

/* ========================================
   NEWS SECTION
   ======================================== */

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

.news-timeline {
    max-width: 800px;
    margin: 0 auto;
}

.news-item {
    display: flex;
    gap: var(--spacing-lg);
    padding: var(--spacing-md);
    border-left: 3px solid var(--primary-color);
    margin-bottom: var(--spacing-md);
    background: var(--bg-secondary);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    transition: all 0.3s ease;
}

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

.news-date {
    font-weight: 600;
    color: var(--primary-color);
    min-width: 90px;
    font-size: 0.9rem;
}

.news-item p {
    margin: 0;
    color: var(--text-secondary);
}

.news-item strong {
    color: var(--text-primary);
}

/* ========================================
   EXPERIENCE SECTION
   ======================================== */

.experience-section {
    background: var(--bg-secondary);
}

.experience-timeline {
    max-width: 900px;
    margin: 0 auto;
}

.experience-item {
    background: var(--bg-color);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    margin-bottom: var(--spacing-lg);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

.experience-item:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
}

.experience-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: var(--spacing-sm);
    flex-wrap: wrap;
    gap: var(--spacing-sm);
}

.experience-item h3 {
    font-size: 1.3rem;
    color: var(--text-primary);
    margin-bottom: var(--spacing-xs);
}

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

.experience-date {
    color: var(--text-secondary);
    font-size: 0.9rem;
    font-weight: 500;
}

.experience-desc {
    margin-bottom: var(--spacing-md);
    line-height: 1.7;
}

.experience-tags {
    display: flex;
    gap: var(--spacing-xs);
    flex-wrap: wrap;
}

.tag {
    padding: 0.25rem 0.75rem;
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    font-size: 0.85rem;
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
}

/* ========================================
   PROJECTS PREVIEW
   ======================================== */

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

.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

.project-card {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

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

.project-card h3 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
    font-size: 1.2rem;
}

.project-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    color: var(--primary-color);
    font-weight: 500;
    margin-top: var(--spacing-sm);
}

/* ========================================
   BUTTONS
   ======================================== */

.btn-primary {
    display: inline-block;
    padding: 0.75rem 2rem;
    background: var(--primary-color);
    color: white;
    font-weight: 600;
    border-radius: var(--radius-lg);
    transition: all 0.3s ease;
    box-shadow: var(--shadow-md);
    border: none;
    cursor: pointer;
}

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
    color: white;
}

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

/* ========================================
   PAGE HEADER
   ======================================== */

.page-header {
    background: linear-gradient(135deg, var(--bg-secondary) 0%, #e0e7ff 100%);
    padding: var(--spacing-2xl) 0;
    text-align: center;
}

.page-header h1 {
    font-size: 3rem;
    margin-bottom: var(--spacing-sm);
}

.page-header p {
    font-size: 1.2rem;
    color: var(--text-secondary);
}

/* ========================================
   PUBLICATIONS PAGE
   ======================================== */

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

.year-section {
    margin-bottom: var(--spacing-2xl);
}

.year-title {
    font-size: 1.8rem;
    color: var(--primary-color);
    margin-bottom: var(--spacing-lg);
    padding-bottom: var(--spacing-sm);
    border-bottom: 2px solid var(--border-color);
}

.publication-item {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    margin-bottom: var(--spacing-lg);
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

.publication-item:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-3px);
}

.publication-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: var(--spacing-sm);
    flex-wrap: wrap;
    gap: var(--spacing-sm);
}

.publication-title {
    flex: 1;
    font-size: 1.3rem;
    color: var(--text-primary);
}

.publication-badges {
    display: flex;
    gap: var(--spacing-xs);
    flex-wrap: wrap;
}

.badge {
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-md);
    font-size: 0.85rem;
    font-weight: 600;
}

.badge-conference {
    background: #dbeafe;
    color: #1e40af;
}

.badge-spotlight {
    background: #fef3c7;
    color: #92400e;
}

.badge-preprint {
    background: #e0e7ff;
    color: #4338ca;
}

.publication-authors {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
}

.publication-authors strong {
    color: var(--text-primary);
}

.publication-venue {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-bottom: var(--spacing-sm);
}

.publication-abstract {
    line-height: 1.7;
    margin: var(--spacing-md) 0;
    padding: var(--spacing-md);
    background: var(--bg-color);
    border-radius: var(--radius-md);
    border-left: 3px solid var(--primary-color);
}

.publication-links {
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
    margin: var(--spacing-md) 0;
}

.pub-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: 0.5rem 1rem;
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    font-weight: 500;
    transition: all 0.3s ease;
}

.pub-link:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
}

.bibtex-container {
    margin-top: var(--spacing-md);
    background: var(--bg-color);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
}

.bibtex-container pre {
    margin: 0;
    overflow-x: auto;
}

.bibtex-container code {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    color: var(--text-primary);
}

.publication-topics {
    display: flex;
    gap: var(--spacing-xs);
    flex-wrap: wrap;
    margin-top: var(--spacing-md);
}

.topic-tag {
    padding: 0.25rem 0.75rem;
    background: var(--bg-color);
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
    border-radius: var(--radius-md);
    font-size: 0.85rem;
}

.cta-box {
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--accent-color) 100%);
    color: white;
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    text-align: center;
    margin-top: var(--spacing-2xl);
}

.cta-box h3 {
    color: white;
    margin-bottom: var(--spacing-sm);
}

.cta-box p {
    color: rgba(255, 255, 255, 0.9);
    margin-bottom: var(--spacing-lg);
}

.cta-box .btn-primary {
    background: white;
    color: var(--primary-color);
}

.cta-box .btn-primary:hover {
    background: var(--bg-secondary);
}

/* ========================================
   PROJECTS PAGE
   ======================================== */

.category-section {
    margin-bottom: var(--spacing-2xl);
}

.category-title {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 2rem;
    margin-bottom: var(--spacing-lg);
    color: var(--text-primary);
}

.category-icon {
    font-size: 2rem;
}

.project-detailed {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    margin-bottom: var(--spacing-lg);
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

.project-detailed:hover {
    box-shadow: var(--shadow-lg);
    transform: translateY(-3px);
}

.project-detailed-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: var(--spacing-md);
    flex-wrap: wrap;
    gap: var(--spacing-sm);
}

.project-detailed-header h3 {
    flex: 1;
    color: var(--text-primary);
}

.github-link {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: 0.5rem 1rem;
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-weight: 500;
    font-size: 0.9rem;
    transition: all 0.3s ease;
}

.github-link:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
}

.project-description {
    line-height: 1.7;
    margin-bottom: var(--spacing-md);
}

.project-tech {
    display: flex;
    gap: var(--spacing-xs);
    flex-wrap: wrap;
}

.tech-badge {
    padding: 0.25rem 0.75rem;
    background: var(--bg-color);
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
    border-radius: var(--radius-md);
    font-size: 0.85rem;
    font-weight: 500;
}

.project-status {
    padding: 0.25rem 0.75rem;
    background: #fef3c7;
    color: #92400e;
    border-radius: var(--radius-md);
    font-size: 0.85rem;
    font-weight: 600;
}

.projects-grid-small {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
}

.small-project-card {
    background: var(--bg-secondary);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

.small-project-card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-3px);
    border-color: var(--primary-color);
}

.small-project-card h4 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-xs);
    font-size: 1.1rem;
}

.small-project-card p {
    font-size: 0.9rem;
    margin-bottom: var(--spacing-sm);
}

.small-tech {
    display: flex;
    gap: var(--spacing-xs);
    flex-wrap: wrap;
}

.small-tech span {
    padding: 0.2rem 0.5rem;
    background: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.achievements-section {
    margin-top: var(--spacing-2xl);
}

.achievement-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
}

.achievement-card {
    background: linear-gradient(135deg, #fef3c7 0%, #fed7aa 100%);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    text-align: center;
    border: 2px solid #fbbf24;
    transition: all 0.3s ease;
}

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

.achievement-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-sm);
}

.achievement-card h4 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-xs);
}

.achievement-card p {
    color: var(--text-secondary);
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.achievement-detail {
    display: block;
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-top: var(--spacing-sm);
}

.achievement-link {
    display: inline-block;
    margin-top: var(--spacing-sm);
    color: var(--primary-color);
    font-weight: 500;
}

/* ========================================
   FOOTER
   ======================================== */

.footer {
    background: var(--text-primary);
    color: white;
    padding: var(--spacing-lg) 0;
    text-align: center;
}

.footer p {
    color: rgba(255, 255, 255, 0.8);
    margin-bottom: var(--spacing-sm);
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: var(--spacing-md);
}

.footer-links a {
    color: white;
    font-size: 1.5rem;
    transition: all 0.3s ease;
}

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

/* ========================================
   ANIMATIONS
   ======================================== */

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ========================================
   RESPONSIVE DESIGN
   ======================================== */

@media (max-width: 968px) {
    .hero-container {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-links {
        justify-content: center;
    }
    
    .hero-image img {
        max-width: 300px;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .research-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background: var(--bg-color);
        width: 100%;
        text-align: center;
        transition: 0.3s;
        box-shadow: var(--shadow-lg);
        padding: var(--spacing-lg) 0;
        gap: var(--spacing-md);
    }
    
    .nav-menu.active {
        left: 0;
    }
    
    .hamburger {
        display: flex;
    }
    
    .hamburger.active .bar:nth-child(2) {
        opacity: 0;
    }
    
    .hamburger.active .bar:nth-child(1) {
        transform: translateY(7px) rotate(45deg);
    }
    
    .hamburger.active .bar:nth-child(3) {
        transform: translateY(-7px) rotate(-45deg);
    }
    
    .hero-title {
        font-size: 2rem;
    }
    
    .page-header h1 {
        font-size: 2rem;
    }
    
    .experience-header,
    .publication-header,
    .project-detailed-header {
        flex-direction: column;
    }
    
    .news-item {
        flex-direction: column;
        gap: var(--spacing-xs);
    }
    
    .projects-grid,
    .projects-grid-small,
    .achievement-grid {
        grid-template-columns: 1fr;
    }
}