/* ========================================
   CSS Variables & Reset
   ======================================== */
:root {
    /* Colors */
    --primary-color: #2563eb;
    --primary-dark: #1e40af;
    --primary-light: #3b82f6;
    --secondary-color: #0ea5e9;
    --accent-color: #f59e0b;
    --success-color: #10b981;
    
    --text-dark: #1f2937;
    --text-medium: #4b5563;
    --text-light: #6b7280;
    
    --bg-white: #ffffff;
    --bg-gray-50: #f9fafb;
    --bg-gray-100: #f3f4f6;
    --bg-gray-800: #1f2937;
    --bg-gray-900: #111827;
    
    --border-color: #e5e7eb;
    --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);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    
    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-mono: 'SF Mono', Monaco, 'Cascadia Code', 'Roboto Mono', Consolas, '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;
    
    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 300ms ease-in-out;
    --transition-slow: 500ms ease-in-out;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    line-height: 1.6;
    color: var(--text-dark);
    background-color: var(--bg-white);
    overflow-x: hidden;
}

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

/* ========================================
   Navigation Bar
   ======================================== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    box-shadow: var(--shadow-sm);
    z-index: 1000;
    transition: var(--transition-base);
}

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

.nav-brand {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-dark);
}

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

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

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

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

.nav-menu a:hover::after {
    width: 100%;
}

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

.hamburger span {
    width: 25px;
    height: 3px;
    background-color: var(--text-dark);
    transition: var(--transition-base);
}

/* ========================================
   Hero Section
   ======================================== */
.hero {
    padding: 8rem var(--spacing-md) 4rem;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    text-align: center;
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 800;
    margin-bottom: var(--spacing-sm);
    animation: fadeInUp 0.8s ease-out;
}

.hero-subtitle {
    font-size: 1.75rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    opacity: 0.95;
    animation: fadeInUp 1s ease-out;
}

.hero-company {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-md);
    opacity: 0.9;
    animation: fadeInUp 1.2s ease-out;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    background-color: rgba(255, 255, 255, 0.2);
    backdrop-filter: blur(10px);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-xl);
    margin-bottom: var(--spacing-lg);
    font-size: 1.1rem;
    font-weight: 600;
    animation: fadeInUp 1.4s ease-out;
}

.hero-badge i {
    font-size: 1.5rem;
    color: var(--accent-color);
}

.hero-description {
    font-size: 1.125rem;
    max-width: 800px;
    margin: 0 auto var(--spacing-lg);
    line-height: 1.8;
    opacity: 0.95;
    animation: fadeInUp 1.6s ease-out;
}

.hero-tags {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xl);
    animation: fadeInUp 1.8s ease-out;
}

.tag {
    background-color: rgba(255, 255, 255, 0.2);
    padding: var(--spacing-xs) var(--spacing-md);
    border-radius: var(--radius-lg);
    font-size: 0.9rem;
    font-weight: 500;
    backdrop-filter: blur(10px);
}

.hero-buttons {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    margin-bottom: var(--spacing-xl);
    animation: fadeInUp 2s ease-out;
}

.btn {
    padding: var(--spacing-sm) var(--spacing-lg);
    border-radius: var(--radius-md);
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition-base);
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
}

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

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

.btn-secondary {
    background-color: transparent;
    color: white;
    border: 2px solid white;
}

.btn-secondary:hover {
    background-color: white;
    color: var(--primary-color);
    transform: translateY(-2px);
}

.social-links {
    display: flex;
    justify-content: center;
    gap: var(--spacing-md);
    animation: fadeInUp 2.2s ease-out;
}

.social-links a {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background-color: rgba(255, 255, 255, 0.2);
    backdrop-filter: blur(10px);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.5rem;
    transition: var(--transition-base);
}

.social-links a:hover {
    background-color: white;
    color: var(--primary-color);
    transform: translateY(-5px);
}

/* ========================================
   Impact Section
   ======================================== */
.impact-section {
    padding: var(--spacing-2xl) var(--spacing-md);
    background-color: var(--bg-gray-50);
}

.section-title {
    font-size: 2.5rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: var(--spacing-xl);
    color: var(--text-dark);
}

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

.impact-card {
    background-color: white;
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    text-align: center;
    transition: var(--transition-base);
}

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

.impact-icon {
  font-family: "Apple Color Emoji","Segoe UI Emoji","Noto Color Emoji",sans-serif;
}


.impact-number {
  font-family: var(--font-sans) !important;   /* force normal text font */
  font-weight: 800;
  font-variant-numeric: normal;
  font-feature-settings: normal;
  letter-spacing: 0;
  white-space: nowrap;
  unicode-bidi: plaintext;                   /* avoid weird glyph substitution */
}


.impact-label {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-dark);
    margin-bottom: var(--spacing-xs);
}

.impact-detail {
    font-size: 0.875rem;
    color: var(--text-light);
}

/* ========================================
   About Section
   ======================================== */
.about-section {
    padding: var(--spacing-2xl) var(--spacing-md);
}

.about-content {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: var(--spacing-xl);
    margin-top: var(--spacing-xl);
}

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

.about-skills h3 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-dark);
}

.skills-tags {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.skill-tag {
    background-color: var(--bg-gray-100);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    font-weight: 500;
    color: var(--text-dark);
    transition: var(--transition-fast);
}

.skill-tag:hover {
    background-color: var(--primary-light);
    color: white;
    transform: translateX(5px);
}

/* ========================================
   Achievements Section
   ======================================== */
.achievements-section {
    padding: var(--spacing-2xl) var(--spacing-md);
    background-color: var(--bg-gray-50);
}

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

.achievement-card {
    background-color: white;
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: var(--transition-base);
}

.achievement-card.featured {
    grid-column: span 2;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

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

.achievement-icon {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-md);
    color: var(--primary-color);
}

.achievement-card.featured .achievement-icon {
    color: var(--accent-color);
}

.achievement-card h3 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-xs);
}

.achievement-year {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-light);
    margin-bottom: var(--spacing-md);
}

.achievement-card.featured .achievement-year {
    color: rgba(255, 255, 255, 0.8);
}

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

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

.tag-small {
    background-color: var(--bg-gray-100);
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 500;
}

.achievement-card.featured .tag-small {
    background-color: rgba(255, 255, 255, 0.2);
    color: white;
}

/* ========================================
   Experience Section (Timeline)
   ======================================== */
.experience-section {
    padding: var(--spacing-2xl) var(--spacing-md);
}

.timeline {
    position: relative;
    padding-left: 2rem;
    margin-top: var(--spacing-xl);
}

.timeline::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 3px;
    background: linear-gradient(to bottom, var(--primary-color), var(--secondary-color));
}

.timeline-item {
    position: relative;
    margin-bottom: var(--spacing-2xl);
}

.timeline-marker {
    position: absolute;
    left: -2.5rem;
    top: 0;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background-color: var(--primary-color);
    border: 4px solid white;
    box-shadow: var(--shadow-md);
}

.timeline-content {
    background-color: white;
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: var(--transition-base);
}

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

.timeline-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-sm);
}

.timeline-header h3 {
    font-size: 1.5rem;
    color: var(--text-dark);
}

.timeline-date {
    background-color: var(--bg-gray-100);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-medium);
}

.timeline-company {
    color: var(--text-medium);
    margin-bottom: var(--spacing-md);
    font-size: 1.1rem;
}

.timeline-company i {
    color: var(--primary-color);
    margin-right: var(--spacing-xs);
}

.experience-subsection {
    margin-bottom: var(--spacing-lg);
}

.experience-subsection h4 {
    font-size: 1.125rem;
    color: var(--primary-color);
    margin-bottom: var(--spacing-sm);
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.experience-subsection ul {
    list-style: none;
    padding-left: 0;
}

.experience-subsection li {
    padding-left: 1.5rem;
    margin-bottom: var(--spacing-sm);
    position: relative;
    line-height: 1.7;
}

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

.tech-stack {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
    margin-top: var(--spacing-md);
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--border-color);
}

.tech-tag {
    background-color: var(--bg-gray-100);
    color: var(--text-dark);
    padding: 0.375rem 0.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 500;
}

/* ========================================
   Research Section
   ======================================== */
.research-section {
    padding: var(--spacing-2xl) var(--spacing-md);
    background-color: var(--bg-gray-50);
}

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

.research-card {
    background-color: white;
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    transition: var(--transition-base);
}

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

.research-icon {
    width: 60px;
    height: 60px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: var(--spacing-md);
}

.research-icon i {
    font-size: 1.75rem;
    color: white;
}

.research-card h3 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-dark);
}

.research-card p {
    line-height: 1.7;
    color: var(--text-medium);
    margin-bottom: var(--spacing-md);
}

.research-keywords {
    list-style: none;
}

.research-keywords li {
    padding: var(--spacing-xs) 0;
    color: var(--text-light);
    font-size: 0.875rem;
    position: relative;
    padding-left: 1rem;
}

.research-keywords li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--primary-color);
}

/* ========================================
   Publications Section
   ======================================== */
.publications-section {
    padding: var(--spacing-2xl) var(--spacing-md);
}

.publications-stats {
    display: flex;
    justify-content: center;
    gap: var(--spacing-xl);
    margin: var(--spacing-xl) 0;
    flex-wrap: wrap;
}

.pub-stat {
    text-align: center;
    padding: var(--spacing-md);
}

.pub-stat i {
    font-size: 2rem;
    color: var(--primary-color);
    margin-bottom: var(--spacing-sm);
}

.stat-number {
    display: block;
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-dark);
}

.stat-label {
    display: block;
    font-size: 1rem;
    color: var(--text-medium);
    font-weight: 600;
}

.stat-detail {
    display: block;
    font-size: 0.875rem;
    color: var(--text-light);
    margin-top: var(--spacing-xs);
}

.publications-list {
    margin-top: var(--spacing-xl);
}

.publication-item {
    display: flex;
    gap: var(--spacing-lg);
    padding: var(--spacing-lg);
    background-color: white;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    margin-bottom: var(--spacing-md);
    transition: var(--transition-base);
}

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

.pub-year {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary-color);
    min-width: 60px;
}

.pub-content h4 {
    font-size: 1.125rem;
    color: var(--text-dark);
    margin-bottom: var(--spacing-xs);
}

.pub-authors {
    font-size: 0.9rem;
    color: var(--text-medium);
    margin-bottom: var(--spacing-xs);
}

.pub-venue {
    font-size: 0.9rem;
    color: var(--text-light);
    margin-bottom: var(--spacing-sm);
}

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

.conference-section,
.service-section {
    margin-top: var(--spacing-2xl);
    padding: var(--spacing-lg);
    background-color: var(--bg-gray-50);
    border-radius: var(--radius-lg);
}

.conference-section h3,
.service-section h3 {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-dark);
}

.conference-section h3 i,
.service-section h3 i {
    color: var(--primary-color);
    margin-right: var(--spacing-xs);
}

.conference-list,
.service-list {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-md);
}

.conference-tag,
.service-tag {
    background-color: white;
    padding: var(--spacing-xs) var(--spacing-md);
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    box-shadow: var(--shadow-sm);
}

/* ========================================
   Skills Section
   ======================================== */
.skills-section {
    padding: var(--spacing-2xl) var(--spacing-md);
    background-color: var(--bg-gray-50);
}

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

.skill-category {
    background-color: white;
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
}

.skill-category h3 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-dark);
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.skill-category h3 i {
    color: var(--primary-color);
}

.skill-items {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
}

.skill-badge {
    background-color: var(--bg-gray-100);
    color: var(--text-dark);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-md);
    font-size: 0.875rem;
    font-weight: 500;
    transition: var(--transition-fast);
}

.skill-badge:hover {
    background-color: var(--primary-color);
    color: white;
    transform: translateY(-2px);
}

/* ========================================
   Contact Section
   ======================================== */
.contact-section {
    padding: var(--spacing-2xl) var(--spacing-md);
}

.contact-intro {
    text-align: center;
    font-size: 1.125rem;
    color: var(--text-medium);
    max-width: 600px;
    margin: 0 auto var(--spacing-xl);
}

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

.contact-card {
    background-color: white;
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    text-align: center;
    text-decoration: none;
    color: inherit;
    transition: var(--transition-base);
}

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

.contact-card i {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: var(--spacing-md);
}

.contact-card h3 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-xs);
    color: var(--text-dark);
}

.contact-card p {
    color: var(--text-medium);
    font-size: 0.9rem;
}

/* ========================================
   Footer
   ======================================== */
.footer {
    background-color: var(--bg-gray-900);
    color: white;
    padding: var(--spacing-xl) var(--spacing-md);
    text-align: center;
}

.footer p {
    margin-bottom: var(--spacing-xs);
}

.footer-note {
    font-size: 0.875rem;
    opacity: 0.7;
}

/* ========================================
   Animations
   ======================================== */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ========================================
   Responsive Design
   ======================================== */
@media (max-width: 1024px) {
    .about-content {
        grid-template-columns: 1fr;
    }
    
    .achievement-card.featured {
        grid-column: span 1;
    }
}

@media (max-width: 768px) {
    .nav-menu {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background-color: white;
        flex-direction: column;
        padding: var(--spacing-md);
        box-shadow: var(--shadow-lg);
        display: none;
    }
    
    .nav-menu.active {
        display: flex;
    }
    
    .hamburger {
        display: flex;
    }
    
    .hero {
        padding: 6rem var(--spacing-md) 3rem;
    }
    
    .hero-title {
        font-size: 2.5rem;
    }
    
    .hero-subtitle {
        font-size: 1.5rem;
    }
    
    .hero-buttons {
        flex-direction: column;
    }
    
    .impact-grid {
        grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    }
    
    .timeline-header {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--spacing-sm);
    }
    
    .publication-item {
        flex-direction: column;
    }
    
    .contact-grid {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }
    
    .section-title {
        font-size: 2rem;
    }
    
    .impact-number {
        font-size: 2rem;
    }
    
    .impact-grid {
        grid-template-columns: 1fr;
    }
}