/* ===================================
   CSS CUSTOM PROPERTIES (VARIABLES)
   =================================== */
:root {
  /* Colors */
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-primary-light: #3b82f6;
  --color-secondary: #64748b;
  --color-accent: #f59e0b;
  --color-text: #1e293b;
  --color-text-light: #64748b;
  --color-text-muted: #94a3b8;
  --color-background: #ffffff;
  --color-background-alt: #f8fafc;
  --color-surface: #ffffff;
  --color-border: #e2e8f0;
  --color-border-light: #f1f5f9;
  
  /* Typography */
  --font-family-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;
  --font-size-5xl: 3rem;
  --font-size-6xl: 3.75rem;
  
  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  --spacing-3xl: 4rem;
  --spacing-4xl: 6rem;
  --spacing-5xl: 8rem;
  
  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
  --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
  
  /* Border Radius */
  --radius-sm: 0.25rem;
  --radius-md: 0.375rem;
  --radius-lg: 0.5rem;
  --radius-xl: 0.75rem;
  --radius-2xl: 1rem;
  --radius-full: 9999px;
  
  /* Transitions */
  --transition-fast: 150ms ease-in-out;
  --transition-base: 300ms ease-in-out;
  --transition-slow: 500ms ease-in-out;
  
  /* Z-index */
  --z-dropdown: 1000;
  --z-sticky: 1020;
  --z-fixed: 1030;
  --z-modal: 1040;
  --z-popover: 1050;
  --z-tooltip: 1060;
}

/* ===================================
   RESET & BASE STYLES
   =================================== */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
  line-height: 1.5;
}

body {
  font-family: var(--font-family-primary);
  font-size: var(--font-size-base);
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-background);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ===================================
   TYPOGRAPHY
   =================================== */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.2;
  margin-bottom: var(--spacing-md);
  color: var(--color-text);
}

h1 { font-size: var(--font-size-4xl); }
h2 { font-size: var(--font-size-3xl); }
h3 { font-size: var(--font-size-2xl); }
h4 { font-size: var(--font-size-xl); }
h5 { font-size: var(--font-size-lg); }
h6 { font-size: var(--font-size-base); }

p {
  margin-bottom: var(--spacing-md);
  color: var(--color-text-light);
}

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

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

ul, ol {
  margin-bottom: var(--spacing-md);
  padding-left: var(--spacing-lg);
}

li {
  margin-bottom: var(--spacing-xs);
  color: var(--color-text-light);
}

strong {
  font-weight: 600;
  color: var(--color-text);
}

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

@media (max-width: 768px) {
  .container {
    padding: 0 var(--spacing-md);
  }
}

.section {
  padding: var(--spacing-5xl) 0;
}

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

.section-header {
  text-align: center;
  margin-bottom: var(--spacing-4xl);
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.section-title {
  font-size: var(--font-size-4xl);
  font-weight: 700;
  margin-bottom: var(--spacing-md);
  position: relative;
}

.section-title::after {
  content: '';
  position: absolute;
  bottom: -var(--spacing-sm);
  left: 50%;
  transform: translateX(-50%);
  width: 60px;
  height: 4px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
  border-radius: var(--radius-full);
}

.section-subtitle {
  font-size: var(--font-size-lg);
  color: var(--color-text-light);
  margin-bottom: 0;
}

/* ===================================
   BUTTONS
   =================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: var(--spacing-md) var(--spacing-xl);
  font-size: var(--font-size-base);
  font-weight: 500;
  text-decoration: none;
  border: 2px solid transparent;
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-base);
  white-space: nowrap;
}

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

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

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

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

/* ===================================
   NAVIGATION
   =================================== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  background-color: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  z-index: var(--z-fixed);
  transition: all var(--transition-base);
  padding: var(--spacing-md) 0;
}

.navbar.scrolled {
  background-color: rgba(255, 255, 255, 0.98);
  box-shadow: var(--shadow-md);
  padding: var(--spacing-sm) 0;
}

/* Navbar Photo Animation */
.navbar-photo {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  object-fit: cover;
  border: 2px solid var(--color-primary);
  opacity: 0;
  transform: scale(0.8);
  transition: all 0.3s ease;
  margin-right: var(--spacing-sm);
}

.navbar.scrolled .navbar-photo {
  opacity: 1;
  transform: scale(1);
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.nav-brand a {
  font-size: var(--font-size-xl);
  font-weight: 600;
  color: var(--color-text);
  text-decoration: none;
  display: flex;
  align-items: center;
}

.nav-menu {
  display: flex;
  gap: var(--spacing-xl);
}

.nav-link {
  font-weight: 500;
  color: var(--color-text-light);
  transition: color var(--transition-fast);
  position: relative;
}

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

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

.nav-link::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--color-primary);
  transition: width var(--transition-base);
}

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

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

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

/* Mobile Navigation */
@media (max-width: 768px) {
  .nav-container {
    padding: 0 var(--spacing-md);
  }
  
  .nav-menu {
    position: fixed;
    top: 100%;
    left: 0;
    right: 0;
    background-color: white;
    flex-direction: column;
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-lg);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
  }
  
  .nav-menu.active {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }
  
  .nav-toggle {
    display: flex;
  }
  
  .nav-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
  }
  
  .nav-toggle.active span:nth-child(2) {
    opacity: 0;
  }
  
  .nav-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(7px, -6px);
  }
}

/* ===================================
   HERO SECTION
   =================================== */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  background: linear-gradient(135deg, var(--color-background) 0%, var(--color-background-alt) 100%);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: url('data:image/svg+xml,<svg width="60" height="60" viewBox="0 0 60 60" xmlns="http://www.w3.org/2000/svg"><g fill="none" fill-rule="evenodd"><g fill="%23e2e8f0" fill-opacity="0.4"><circle cx="30" cy="30" r="2"/></g></svg>');
  opacity: 0.3;
}

.hero-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
  position: relative;
  z-index: 1;
}

.hero-content {
  display: grid;
  grid-template-columns: 1fr 400px;
  gap: var(--spacing-4xl);
  align-items: center;
}

.hero-title {
  margin-bottom: var(--spacing-xl);
}

.title-main {
  display: block;
  font-size: var(--font-size-5xl);
  font-weight: 700;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: var(--spacing-sm);
  animation: fadeInUp 1s ease-out;
}

.title-sub {
  display: block;
  font-size: var(--font-size-xl);
  font-weight: 500;
  color: var(--color-text-light);
  animation: fadeInUp 1s ease-out 0.2s both;
}

.hero-description {
  font-size: var(--font-size-lg);
  color: var(--color-text-light);
  margin-bottom: var(--spacing-xl);
  animation: fadeInUp 1s ease-out 0.4s both;
}

.hero-social {
  display: flex;
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
  animation: fadeInUp 1s ease-out 0.6s both;
}

.social-link {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  background-color: var(--color-surface);
  border: 2px solid var(--color-border);
  border-radius: var(--radius-full);
  color: var(--color-text-light);
  font-size: var(--font-size-xl);
  transition: all var(--transition-base);
}

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

.hero-cta {
  display: flex;
  gap: var(--spacing-lg);
  animation: fadeInUp 1s ease-out 0.8s both;
}

.hero-image {
  display: flex;
  justify-content: center;
  animation: fadeInUp 1s ease-out 1s both;
}

.image-placeholder {
  width: 300px;
  height: 300px;
  background: linear-gradient(135deg, var(--color-background-alt), var(--color-surface));
  border: 3px solid var(--color-border);
  border-radius: var(--radius-2xl);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  color: var(--color-text-muted);
  box-shadow: var(--shadow-xl);
}

.image-placeholder i {
  font-size: 4rem;
  margin-bottom: var(--spacing-md);
}

.profile-photo {
  width: 300px;
  height: 300px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid var(--color-border);
  box-shadow: var(--shadow-xl);
  transition: all var(--transition-base);
  animation: fadeInUp 1s ease-out 1s both;
}

.profile-photo:hover {
  transform: scale(1.05);
  border-color: var(--color-primary);
  box-shadow: var(--shadow-2xl), 0 0 30px rgba(var(--color-primary-rgb), 0.3);
}

.hero-scroll {
  position: absolute;
  bottom: var(--spacing-xl);
  left: 50%;
  transform: translateX(-50%);
  animation: bounce 2s infinite;
}

.scroll-indicator {
  color: var(--color-text-muted);
  font-size: var(--font-size-lg);
  transition: color var(--transition-fast);
}

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

/* Mobile Hero */
@media (max-width: 768px) {
  .hero-content {
    grid-template-columns: 1fr;
    gap: var(--spacing-2xl);
    text-align: center;
  }
  
  .title-main {
    font-size: var(--font-size-4xl);
  }
  
  .title-sub {
    font-size: var(--font-size-lg);
  }
  
  .hero-cta {
    flex-direction: column;
    align-items: center;
  }
  
  .image-placeholder {
    width: 250px;
    height: 250px;
  }
}

/* ===================================
   ABOUT SECTION
   =================================== */
.about-content {
  max-width: 800px;
  margin: 0 auto;
}

.about-card {
  background-color: var(--color-surface);
  padding: var(--spacing-xl);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  margin-bottom: var(--spacing-xl);
  transition: transform var(--transition-base);
}

.about-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.about-card h3 {
  color: var(--color-primary);
  margin-bottom: var(--spacing-md);
  font-size: var(--font-size-xl);
}

/* ===================================
   RESEARCH SECTION
   =================================== */
.research-filters {
  display: flex;
  justify-content: center;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-3xl);
  flex-wrap: wrap;
}

.filter-btn {
  padding: var(--spacing-sm) var(--spacing-lg);
  background-color: var(--color-surface);
  border: 2px solid var(--color-border);
  border-radius: var(--radius-full);
  color: var(--color-text-light);
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-base);
}

.filter-btn:hover,
.filter-btn.active {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: white;
}

.publications-grid {
  display: grid;
  gap: var(--spacing-xl);
}

.publication-card {
  background-color: var(--color-surface);
  padding: var(--spacing-xl);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  transition: all var(--transition-base);
  border-left: 4px solid var(--color-primary);
}

.publication-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

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

.publication-header h3 {
  margin-bottom: 0;
  color: var(--color-text);
  flex: 1;
}

.publication-year {
  background-color: var(--color-primary);
  color: white;
  padding: var(--spacing-xs) var(--spacing-md);
  border-radius: var(--radius-full);
  font-size: var(--font-size-sm);
  font-weight: 600;
  white-space: nowrap;
}

.publication-authors {
  font-size: var(--font-size-sm);
  color: var(--color-text-light);
  margin-bottom: var(--spacing-sm);
}

.publication-venue {
  font-style: italic;
  color: var(--color-text-light);
  margin-bottom: var(--spacing-md);
}

.publication-description {
  margin-bottom: var(--spacing-lg);
  color: var(--color-text-light);
}

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

.pub-link {
  color: var(--color-primary);
  font-size: var(--font-size-sm);
  font-weight: 500;
  text-decoration: none;
  padding: var(--spacing-xs) var(--spacing-sm);
  border: 1px solid var(--color-primary);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

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

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

.tag {
  background-color: var(--color-background-alt);
  color: var(--color-text-light);
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--radius-md);
  font-size: var(--font-size-xs);
  font-weight: 500;
}

/* ===================================
   TEACHING SECTION
   =================================== */
.teaching-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--spacing-xl);
  margin-bottom: var(--spacing-3xl);
}

.teaching-card {
  background-color: var(--color-surface);
  padding: var(--spacing-xl);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  text-align: center;
  transition: transform var(--transition-base);
}

.teaching-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.card-icon {
  width: 80px;
  height: 80px;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto var(--spacing-lg);
  color: white;
  font-size: var(--font-size-2xl);
}

.teaching-card h3 {
  margin-bottom: var(--spacing-lg);
  color: var(--color-primary);
}

.teaching-card ul {
  text-align: left;
  margin-bottom: 0;
}

.teaching-philosophy {
  background-color: var(--color-surface);
  padding: var(--spacing-2xl);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  text-align: center;
}

.teaching-philosophy h3 {
  color: var(--color-primary);
  margin-bottom: var(--spacing-lg);
}

/* ===================================
   TALKS SECTION
   =================================== */
.timeline {
  position: relative;
  max-width: 800px;
  margin: 0 auto;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 50%;
  top: 0;
  bottom: 0;
  width: 2px;
  background-color: var(--color-border);
  transform: translateX(-50%);
}

.timeline-item {
  position: relative;
  margin-bottom: var(--spacing-3xl);
}

.timeline-item:nth-child(odd) .timeline-content {
  margin-left: 0;
  margin-right: 50%;
  padding-right: var(--spacing-xl);
}

.timeline-item:nth-child(even) .timeline-content {
  margin-left: 50%;
  margin-right: 0;
  padding-left: var(--spacing-xl);
}

.timeline-date {
  position: absolute;
  left: 50%;
  top: 0;
  transform: translateX(-50%);
  background-color: var(--color-primary);
  color: white;
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius-full);
  font-weight: 600;
  font-size: var(--font-size-sm);
  z-index: 1;
}

.talk-card {
  background-color: var(--color-surface);
  padding: var(--spacing-xl);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  transition: transform var(--transition-base);
}

.talk-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.talk-card h3 {
  margin-bottom: var(--spacing-md);
  color: var(--color-text);
}

.talk-meta {
  display: flex;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-md);
  flex-wrap: wrap;
}

.talk-type {
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--radius-md);
  font-size: var(--font-size-xs);
  font-weight: 600;
  text-transform: uppercase;
}

.talk-type.speaker {
  background-color: #dbeafe;
  color: #1e40af;
}

.talk-type.organizer {
  background-color: #fef3c7;
  color: #92400e;
}

.talk-type.participant {
  background-color: #d1fae5;
  color: #065f46;
}

.talk-location {
  color: var(--color-text-light);
  font-style: italic;
  font-size: var(--font-size-sm);
}

/* Mobile Timeline */
@media (max-width: 768px) {
  .timeline::before {
    left: var(--spacing-lg);
  }
  
  .timeline-item:nth-child(odd) .timeline-content,
  .timeline-item:nth-child(even) .timeline-content {
    margin-left: var(--spacing-3xl);
    margin-right: 0;
    padding-left: var(--spacing-lg);
    padding-right: 0;
  }
  
  .timeline-date {
    left: var(--spacing-lg);
  }
}

/* ===================================
   PROJECTS SECTION
   =================================== */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
  gap: var(--spacing-xl);
}

.project-card {
  background-color: var(--color-surface);
  padding: var(--spacing-xl);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  transition: transform var(--transition-base);
  border: 1px solid var(--color-border);
}

.project-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.project-card.featured {
  background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent) 100%);
  color: white;
  border: none;
}

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

.project-header h3 {
  margin-bottom: 0;
  flex: 1;
}

.project-card.featured h3 {
  color: white;
}

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

.tech-tag {
  background-color: rgba(255, 255, 255, 0.1);
  color: white;
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--radius-md);
  font-size: var(--font-size-xs);
  font-weight: 500;
  backdrop-filter: blur(10px);
}

.project-card:not(.featured) .tech-tag {
  background-color: var(--color-background-alt);
  color: var(--color-text-light);
}

.project-description {
  margin-bottom: var(--spacing-lg);
}

.project-card.featured .project-description p {
  color: rgba(255, 255, 255, 0.9);
}

.project-features {
  margin-bottom: var(--spacing-lg);
}

.project-card.featured .project-features li {
  color: rgba(255, 255, 255, 0.9);
}

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

.project-link {
  color: var(--color-primary);
  font-size: var(--font-size-sm);
  font-weight: 500;
  text-decoration: none;
  padding: var(--spacing-sm) var(--spacing-md);
  border: 2px solid var(--color-primary);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.project-card.featured .project-link {
  color: white;
  border-color: white;
}

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

.project-card.featured .project-link:hover {
  background-color: white;
  color: var(--color-primary);
}

/* ===================================
   CONTACT SECTION
   =================================== */
.contact-content {
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: var(--spacing-4xl);
  max-width: 1000px;
  margin: 0 auto;
}

.contact-info {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xl);
}

.contact-card {
  background-color: var(--color-surface);
  padding: var(--spacing-xl);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  text-align: center;
  transition: transform var(--transition-base);
}

.contact-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.contact-card i {
  font-size: var(--font-size-2xl);
  color: var(--color-primary);
  margin-bottom: var(--spacing-md);
}

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

.contact-card p {
  margin-bottom: 0;
  color: var(--color-text-light);
  font-size: var(--font-size-sm);
}

.contact-form {
  background-color: var(--color-surface);
  padding: var(--spacing-2xl);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
}

.form-group {
  margin-bottom: var(--spacing-lg);
}

.form-group label {
  display: block;
  margin-bottom: var(--spacing-sm);
  font-weight: 500;
  color: var(--color-text);
}

.form-group input,
.form-group textarea {
  width: 100%;
  padding: var(--spacing-md);
  border: 2px solid var(--color-border);
  border-radius: var(--radius-lg);
  font-family: inherit;
  font-size: var(--font-size-base);
  transition: border-color var(--transition-fast);
  background-color: var(--color-background);
}

.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-group textarea {
  resize: vertical;
  min-height: 120px;
}

.honeypot {
  position: absolute;
  left: -9999px;
  opacity: 0;
}

/* Mobile Contact */
@media (max-width: 768px) {
  .contact-content {
    grid-template-columns: 1fr;
    gap: var(--spacing-2xl);
  }
  
  .contact-info {
    order: 2;
  }
}

/* ===================================
   FOOTER
   =================================== */
.footer {
  background-color: var(--color-text);
  color: white;
  padding: var(--spacing-xl) 0;
}

.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

.footer-links {
  display: flex;
  gap: var(--spacing-lg);
}

.footer-links a {
  color: rgba(255, 255, 255, 0.8);
  transition: color var(--transition-fast);
}

.footer-links a:hover {
  color: white;
}

@media (max-width: 768px) {
  .footer-content {
    flex-direction: column;
    gap: var(--spacing-md);
    text-align: center;
    padding: 0 var(--spacing-md);
  }
}

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

@keyframes bounce {
  0%, 20%, 53%, 80%, 100% {
    transform: translateX(-50%) translateY(0);
  }
  40%, 43% {
    transform: translateX(-50%) translateY(-10px);
  }
  70% {
    transform: translateX(-50%) translateY(-5px);
  }
  90% {
    transform: translateX(-50%) translateY(-2px);
  }
}

/* Intersection Observer Animations */
.animate-on-scroll {
  opacity: 0;
  transform: translateY(30px);
  transition: all 0.8s ease-out;
}

.animate-on-scroll.animate {
  opacity: 1;
  transform: translateY(0);
}

/* ===================================
   RESPONSIVE DESIGN
   =================================== */
@media (max-width: 1024px) {
  .hero-content {
    grid-template-columns: 1fr 300px;
    gap: var(--spacing-3xl);
  }
  
  .image-placeholder {
    width: 250px;
    height: 250px;
  }
}

@media (max-width: 768px) {
  .section {
    padding: var(--spacing-4xl) 0;
  }
  
  .section-title {
    font-size: var(--font-size-3xl);
  }
  
  .projects-grid {
    grid-template-columns: 1fr;
  }
  
  .teaching-grid {
    grid-template-columns: 1fr;
  }
  
  .hero-cta {
    flex-direction: column;
    align-items: stretch;
  }
  
  .btn {
    text-align: center;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--spacing-sm);
  }
  
  .section {
    padding: var(--spacing-3xl) 0;
  }
  
  .hero {
    padding-top: 80px;
    min-height: 80vh; /* Reduce height on mobile */
  }
  
  .hero-content {
    grid-template-columns: 1fr; /* Single column */
    gap: var(--spacing-lg);
  }
  
  .title-main {
    font-size: var(--font-size-3xl);
  }
  
  .title-sub {
    font-size: var(--font-size-base);
  }
  
  .hero-social {
    justify-content: center;
  }
  
  /* Hide image on small mobile screens */
  .hero-image {
    display: none;
  }
  
  .image-placeholder,
  .profile-photo {
    display: none;
  }
  
  /* Make navigation more mobile-friendly */
  .nav-menu {
    font-size: 0.9rem;
  }
}

/* ===================================
   ACCESSIBILITY
   =================================== */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  
  html {
    scroll-behavior: auto;
  }
}

/* Focus states for keyboard navigation */
a:focus,
button:focus,
input:focus,
textarea:focus {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* High contrast mode support */
@media (prefers-contrast: high) {
  :root {
    --color-border: #000000;
    --color-text: #000000;
    --color-background: #ffffff;
  }
}

/* ===================================
   PRINT STYLES
   =================================== */
@media print {
  .navbar,
  .hero-scroll,
  .contact-form,
  .btn {
    display: none;
  }
  
  body {
    font-size: 12pt;
    line-height: 1.4;
  }
  
  .section {
    page-break-inside: avoid;
    margin: 1cm 0;
  }
  
  .section-title {
    color: #000000;
  }
}