/* ===================================
   CSS Custom Properties (Variables)
   =================================== */
:root {
    /* Light Mode Colors */
    --primary-color: #1e3a8a;
    --secondary-color: #0d9488;
    --accent-color: #3b82f6;
    --text-primary: #1f2937;
    --text-secondary: #6b7280;
    --bg-primary: #ffffff;
    --bg-secondary: #f9fafb;
    --bg-tertiary: #f3f4f6;
    --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-primary: 'Inter', sans-serif;
    --font-display: 'Playfair Display', serif;
    
    /* 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: 250ms ease-in-out;
    --transition-slow: 350ms ease-in-out;
}

/* Dark Mode Colors */
[data-theme="dark"] {
    --primary-color: #60a5fa;
    --secondary-color: #14b8a6;
    --accent-color: #3b82f6;
    --text-primary: #f9fafb;
    --text-secondary: #d1d5db;
    --bg-primary: #111827;
    --bg-secondary: #1f2937;
    --bg-tertiary: #374151;
    --border-color: #374151;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.6);
}

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

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-primary);
    color: var(--text-primary);
    background-color: var(--bg-primary);
    line-height: 1.6;
    transition: background-color var(--transition-base), color var(--transition-base);
}

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

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

/* Typography */
h1, h2, h3, h4, h5, h6 {
    line-height: 1.2;
    font-weight: 700;
    margin-bottom: var(--spacing-md);
}

h1 {
    font-size: clamp(2.5rem, 5vw, 4rem);
}

h2 {
    font-size: clamp(2rem, 4vw, 3rem);
}

h3 {
    font-size: clamp(1.5rem, 3vw, 2rem);
}

h4 {
    font-size: 1.25rem;
}

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

.lead {
    font-size: 1.25rem;
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: var(--spacing-lg);
}

a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color var(--transition-fast);
}

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

/* Section Titles */
.section-title {
    font-family: var(--font-display);
    text-align: center;
    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(--secondary-color));
    border-radius: 2px;
}

.subsection-title {
    font-size: 1.75rem;
    margin-bottom: var(--spacing-lg);
    margin-top: var(--spacing-xl);
    color: var(--text-primary);
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    transition: all var(--transition-base);
    cursor: pointer;
    border: 2px solid transparent;
    text-decoration: none;
}

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

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

.btn-secondary {
    background: transparent;
    color: var(--primary-color);
    border-color: var(--primary-color);
}

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

/* ===================================
   Theme Toggle
   =================================== */
.theme-toggle {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 1000;
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    width: 50px;
    height: 50px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all var(--transition-base);
    box-shadow: var(--shadow-md);
}

.theme-toggle:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-lg);
}

.theme-toggle i {
    font-size: 1.25rem;
    color: var(--text-primary);
}

/* ===================================
   Navigation
   =================================== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: var(--bg-primary);
    box-shadow: var(--shadow-md);
    z-index: 999;
    transition: all var(--transition-base);
}

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

.nav-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 1rem var(--spacing-lg);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--primary-color);
    font-family: var(--font-display);
}

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

.nav-link {
    color: var(--text-primary);
    font-weight: 500;
    padding: 0.5rem 0;
    position: relative;
    transition: color var(--transition-fast);
}

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

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

/* Language Toggle */
.language-toggle {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-left: 20px;
}

.lang-link {
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 600;
    font-size: 0.9rem;
    padding: 4px 8px;
    border-radius: 4px;
    transition: all var(--transition-base);
}

.lang-link:hover {
    background: var(--card-bg);
    color: var(--primary-color);
}

.lang-link.active {
    background: var(--primary-color);
    color: white;
}

.lang-separator {
    color: var(--text-secondary);
}

.hamburger {
    display: none;
    flex-direction: column;
    gap: 5px;
    cursor: pointer;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: var(--text-primary);
    border-radius: 2px;
    transition: all var(--transition-base);
}

/* ===================================
   Hero Section
   =================================== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
    padding-top: 80px;
}

.hero-background {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-primary) 100%);
    z-index: -1;
}

.hero-background::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-image: 
        radial-gradient(circle at 20% 50%, rgba(59, 130, 246, 0.1) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(13, 148, 136, 0.1) 0%, transparent 50%);
}

.hero-content {
    display: grid;
    grid-template-columns: 1.2fr 0.8fr;
    gap: var(--spacing-xl);
    align-items: center;
}

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

.hero-name {
    display: block;
    font-family: var(--font-display);
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.5rem;
    color: var(--text-primary);
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.hero-institution {
    margin-bottom: var(--spacing-md);
}

.institution-logo {
    height: 50px;
    width: auto;
    object-fit: contain;
    transition: opacity var(--transition-fast);
}

.hero-institution a:hover .institution-logo {
    opacity: 0.8;
}

.footer-logo {
    margin-bottom: var(--spacing-md);
}

.footer-institution-logo {
    height: 40px;
    width: auto;
    object-fit: contain;
    opacity: 0.85;
    transition: opacity var(--transition-fast);
}

.footer-institution-logo:hover {
    opacity: 1;
}

.hero-tagline {
    font-size: 1.1rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin-bottom: var(--spacing-lg);
    line-height: 1.8;
}

.hero-buttons {
    display: flex;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
    flex-wrap: wrap;
}

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

.hero-social a {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-secondary);
    border-radius: 50%;
    color: var(--text-primary);
    transition: all var(--transition-base);
    border: 2px solid var(--border-color);
}

.hero-social a:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
}

.hero-image {
    display: flex;
    justify-content: center;
    align-items: center;
}

.profile-photo {
    width: 350px;
    height: 350px;
    object-fit: cover;
    border-radius: 50%;
    border: 4px solid var(--border-color);
    box-shadow: var(--shadow-xl);
}

.scroll-indicator {
    position: absolute;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%);
}

.scroll-indicator a {
    color: var(--text-secondary);
    font-size: 2rem;
    animation: bounce 2s infinite;
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        transform: translateY(0);
    }
    40% {
        transform: translateY(-10px);
    }
    60% {
        transform: translateY(-5px);
    }
}

/* ===================================
   About Section
   =================================== */
.about {
    background: var(--bg-secondary);
}

.about-content {
    display: grid;
    grid-template-columns: 1.5fr 1fr;
    gap: var(--spacing-xl);
}

.about-text p {
    color: var(--text-secondary);
    font-size: 1.05rem;
    margin-bottom: var(--spacing-md);
}

.research-interests {
    margin-top: var(--spacing-xl);
}

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

.interests-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-md);
}

.interest-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm);
    background: var(--bg-primary);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    transition: all var(--transition-base);
}

.interest-item:hover {
    transform: translateX(5px);
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
}

.interest-item i {
    color: var(--primary-color);
    font-size: 1.5rem;
}

.interest-item span {
    color: var(--text-primary);
    font-weight: 500;
}

.about-highlights {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

.highlight-card {
    background: var(--bg-primary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
}

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

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

.highlight-card h3 {
    color: var(--text-primary);
    font-size: 1.25rem;
    margin-bottom: var(--spacing-md);
}

.highlight-card ul {
    list-style: none;
    color: var(--text-secondary);
}

.highlight-card li {
    padding-left: 1.5rem;
    position: relative;
    margin-bottom: var(--spacing-sm);
}

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

.expertise-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
}

.tag {
    padding: 0.5rem 1rem;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 0.9rem;
    font-weight: 500;
    transition: all var(--transition-fast);
}

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

/* ===================================
   Research Section
   =================================== */
.research-subsection {
    margin-bottom: var(--spacing-2xl);
}

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

.publication-card {
    background: var(--bg-secondary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    transition: all var(--transition-base);
    position: relative;
}

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

.publication-year {
    position: absolute;
    top: var(--spacing-md);
    right: var(--spacing-md);
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-weight: 700;
    font-size: 0.9rem;
}

.publication-card h4 {
    color: var(--text-primary);
    font-size: 1.1rem;
    margin-bottom: var(--spacing-sm);
    padding-right: 60px;
    line-height: 1.4;
}

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

.publication-journal {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: var(--spacing-md);
}

.publication-link {
    color: var(--primary-color);
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    transition: all var(--transition-fast);
}

.publication-link:hover {
    color: var(--secondary-color);
    gap: 0.75rem;
}

/* Projects Timeline */
.projects-timeline {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xl);
}

.project-item {
    display: grid;
    grid-template-columns: 150px 1fr;
    gap: var(--spacing-lg);
    padding: var(--spacing-lg);
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    border-left: 4px solid var(--primary-color);
    transition: all var(--transition-base);
}

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

.project-date {
    font-weight: 700;
    color: var(--primary-color);
    font-size: 1.1rem;
}

.project-content h4 {
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
}

.project-funding {
    color: var(--secondary-color);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.project-funding i {
    margin-right: 0.5rem;
}

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

.project-role {
    display: inline-block;
    background: var(--bg-primary);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-weight: 600;
    font-size: 0.9rem;
    margin-top: var(--spacing-sm);
}

/* Manuscripts */
.manuscripts-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.manuscript-item {
    display: flex;
    gap: var(--spacing-md);
    padding: var(--spacing-md);
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    transition: all var(--transition-base);
}

.manuscript-item:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
}

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

.manuscript-item strong {
    color: var(--text-primary);
    display: block;
    margin-bottom: 0.25rem;
}

.manuscript-item p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin: 0;
}

/* ===================================
   Teaching Section
   =================================== */
.teaching {
    background: var(--bg-secondary);
}

.teaching-intro {
    max-width: 900px;
    margin: 0 auto var(--spacing-xl);
    text-align: center;
}

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

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

.curriculum-card {
    background: var(--bg-primary);
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    border: 2px solid var(--border-color);
    transition: all var(--transition-base);
    position: relative;
}

.curriculum-card.featured {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-lg);
}

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

.curriculum-icon {
    width: 70px;
    height: 70px;
    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);
}

.curriculum-icon i {
    color: white;
    font-size: 2rem;
}

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

.curriculum-role {
    color: var(--secondary-color);
    font-weight: 600;
    display: block;
    margin-bottom: var(--spacing-md);
}

.curriculum-card p {
    color: var(--text-secondary);
}

.launch-badge {
    display: inline-block;
    background: var(--secondary-color);
    color: white;
    padding: 0.5rem 1rem;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 0.9rem;
    margin-top: var(--spacing-md);
}

/* Courses Grid */
.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--spacing-lg);
}

.course-card {
    background: var(--bg-primary);
    padding: var(--spacing-lg);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    transition: all var(--transition-base);
}

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

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

.course-header i {
    color: var(--primary-color);
    font-size: 1.75rem;
}

.course-level {
    background: var(--primary-color);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
    font-weight: 600;
}

.course-card h4 {
    color: var(--text-primary);
    font-size: 1.15rem;
    margin-bottom: var(--spacing-sm);
}

.course-semester {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

/* Teaching Stats */
.teaching-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-lg);
    margin: var(--spacing-2xl) 0;
}

.stat-card {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    text-align: center;
    color: white;
    box-shadow: var(--shadow-lg);
}

.stat-number {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
}

.stat-label {
    font-size: 1rem;
    opacity: 0.95;
}

/* Teaching Timeline */
.teaching-timeline {
    position: relative;
    padding-left: var(--spacing-xl);
}

.teaching-timeline::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    bottom: 0;
    width: 3px;
    background: var(--border-color);
}

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

.timeline-marker {
    position: absolute;
    left: -11px;
    top: 5px;
    width: 20px;
    height: 20px;
    background: var(--primary-color);
    border-radius: 50%;
    border: 3px solid var(--bg-secondary);
}

.timeline-content h4 {
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.timeline-period {
    color: var(--secondary-color);
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

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

/* ===================================
   Contact Section
   =================================== */
.contact-content {
    display: grid;
    grid-template-columns: 1.5fr 1fr;
    gap: var(--spacing-xl);
    max-width: 1000px;
    margin: 0 auto;
}

.contact-details {
    margin: var(--spacing-xl) 0;
}

.contact-item {
    display: flex;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.contact-icon {
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.contact-icon i {
    color: white;
    font-size: 1.25rem;
}

.contact-item h4 {
    color: var(--text-primary);
    font-size: 1rem;
    margin-bottom: 0.25rem;
}

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

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

.social-links {
    display: flex;
    gap: var(--spacing-md);
    margin-top: var(--spacing-lg);
}

.social-link {
    width: 50px;
    height: 50px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: 50%;
    color: var(--text-primary);
    transition: all var(--transition-base);
}

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

.cta-box {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    padding: var(--spacing-xl);
    border-radius: var(--radius-lg);
    text-align: center;
    color: white;
    box-shadow: var(--shadow-xl);
}

.cta-box i {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
}

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

.cta-box p {
    opacity: 0.95;
    margin-bottom: var(--spacing-lg);
}

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

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

/* ===================================
   Footer
   =================================== */
.footer {
    background: var(--bg-secondary);
    padding: var(--spacing-xl) 0;
    text-align: center;
    border-top: 1px solid var(--border-color);
}

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

.footer-note {
    font-size: 0.9rem;
    opacity: 0.8;
}

/* ===================================
   Responsive Design
   =================================== */
@media (max-width: 968px) {
    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .hero-image {
        order: -1;
    }
    
    .profile-photo {
        width: 250px;
        height: 250px;
    }
    
    .hero-buttons {
        justify-content: center;
    }
    
    .hero-social {
        justify-content: center;
    }
    
    .about-content {
        grid-template-columns: 1fr;
    }
    
    .interests-grid {
        grid-template-columns: 1fr;
    }
    
    .contact-content {
        grid-template-columns: 1fr;
    }
    
    .project-item {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    html {
        font-size: 14px;
    }
    
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 70px;
        flex-direction: column;
        background: var(--bg-primary);
        width: 100%;
        text-align: center;
        transition: left var(--transition-base);
        box-shadow: var(--shadow-lg);
        padding: var(--spacing-lg) 0;
    }
    
    .nav-menu.active {
        left: 0;
    }
    
    .hamburger {
        display: flex;
    }
    
    .hamburger.active span:nth-child(1) {
        transform: rotate(45deg) translate(8px, 8px);
    }
    
    .hamburger.active span:nth-child(2) {
        opacity: 0;
    }
    
    .hamburger.active span:nth-child(3) {
        transform: rotate(-45deg) translate(8px, -8px);
    }
    
    .theme-toggle {
        top: 15px;
        right: 70px;
        width: 45px;
        height: 45px;
    }
    
    section {
        padding: var(--spacing-xl) 0;
    }
    
    .teaching-stats {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-md);
    }
    
    .hero-buttons {
        flex-direction: column;
        width: 100%;
    }
    
    .btn {
        width: 100%;
        justify-content: center;
    }
    
    .publications-grid,
    .courses-grid {
        grid-template-columns: 1fr;
    }
    
    .curriculum-cards {
        grid-template-columns: 1fr;
    }
    
    .teaching-stats {
        grid-template-columns: 1fr;
    }
}

/* ===================================
   Print Styles
   =================================== */
@media print {
    .navbar,
    .theme-toggle,
    .hamburger,
    .hero-buttons,
    .scroll-indicator,
    .footer {
        display: none;
    }
    
    body {
        background: white;
        color: black;
    }
    
    section {
        page-break-inside: avoid;
    }
}