:root {
  /* Light theme colors */
  --color-bg: #f8f9fa;
  --color-text: #212529;
  --color-primary: #0056b3;
  --color-secondary: #6c757d;
  --color-accent: #17a2b8;
  --color-card-bg: #ffffff;
  --color-card-border: #e9ecef;
  --color-header-bg: rgba(255, 255, 255, 0.95);
  --color-footer-bg: #f1f3f5;
  --color-code-bg: #f5f5f5;
  --color-timeline-bg: #e9ecef;
  --color-timeline-marker: var(--color-primary);
  --color-shadow: rgba(0, 0, 0, 0.05);
  --color-btn-hover: #004494;
  --color-link-hover: #004494;
  
  /* Font families */
  --font-main: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
  --font-heading: 'Atkinson Hyperlegible', var(--font-main);
  --font-code: 'JetBrains Mono', monospace;
  
  /* Font sizes */
  --font-size-base: 1rem;
  --font-size-sm: 0.875rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.75rem;
  --font-size-4xl: 2rem;
  
  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 0.75rem;
  --spacing-lg: 1.25rem;
  --spacing-xl: 1.75rem;
  --spacing-2xl: 2.5rem;
  --spacing-3xl: 3rem;
  
  /* Border radius */
  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-full: 9999px;
  
  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
  
  /* Container width */
  --container-width: 1200px;
}

/* Dark theme colors */
.dark-mode {
  --color-bg: #121212;
  --color-text: #e9ecef;
  --color-primary: #4dabf7;
  --color-secondary: #adb5bd;
  --color-accent: #15aabf;
  --color-card-bg: #1e1e1e;
  --color-card-border: #333;
  --color-header-bg: rgba(18, 18, 18, 0.95);
  --color-footer-bg: #1a1a1a;
  --color-code-bg: #2d2d2d;
  --color-timeline-bg: #333;
  --color-timeline-marker: var(--color-primary);
  --color-shadow: rgba(0, 0, 0, 0.2);
  --color-btn-hover: #339af0;
  --color-link-hover: #74c0fc;
}

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

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

body {
  font-family: var(--font-main);
  font-size: var(--font-size-base);
  line-height: 1.5;
  color: var(--color-text);
  background-color: var(--color-bg);
  transition: background-color var(--transition-normal), color var(--transition-normal);
}

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

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

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

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);
}

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

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

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

code {
  font-family: var(--font-code);
  font-size: 0.9em;
  background-color: var(--color-code-bg);
  padding: 0.2em 0.4em;
  border-radius: var(--radius-sm);
}

pre {
  font-family: var(--font-code);
  background-color: var(--color-code-bg);
  padding: var(--spacing-md);
  border-radius: var(--radius-md);
  overflow-x: auto;
  margin-bottom: var(--spacing-md);
}

pre code {
  background-color: transparent;
  padding: 0;
}

/* Container */
.container {
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

/* Header */
header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  background-color: var(--color-header-bg);
  box-shadow: 0 2px 10px var(--color-shadow);
  z-index: 1000;
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 60px;
}

.logo a {
  font-family: var(--font-heading);
  font-size: var(--font-size-xl);
  font-weight: 700;
  color: var(--color-text);
}

.nav-links {
  display: flex;
  list-style: none;
  align-items: center;
}

.nav-links li {
  margin-left: var(--spacing-md);
}

.nav-links a {
  color: var(--color-text);
  font-weight: 500;
  position: relative;
  font-size: var(--font-size-sm);
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: -3px;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--color-primary);
  transition: width var(--transition-normal);
}

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

.theme-toggle button {
  background: none;
  border: none;
  color: var(--color-text);
  cursor: pointer;
  font-size: var(--font-size-lg);
  padding: var(--spacing-xs);
}

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

.nav-toggle span {
  width: 25px;
  height: 3px;
  background-color: var(--color-text);
  margin: 2px 0;
  transition: var(--transition-fast);
}

/* Main content */
main {
  padding-top: 60px;
}

/* About section */
.about {
  padding: var(--spacing-2xl) 0;
}

.about-content {
  max-width: 1000px;
  margin: 0 auto;
}

.about-grid {
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: var(--spacing-xl);
  align-items: start;
}

.about-image {
  text-align: center;
}

.about-image img {
  width: 180px;
  height: 180px;
  border-radius: 50%;
  object-fit: cover;
  border: 3px solid var(--color-primary);
  margin-bottom: var(--spacing-md);
}

.about-text h1 {
  margin-bottom: var(--spacing-xs);
}

.about-text h2 {
  color: var(--color-secondary);
  font-size: var(--font-size-xl);
  margin-bottom: var(--spacing-md);
}

.social-links {
  display: flex;
  gap: var(--spacing-md);
  justify-content: center;
  margin-bottom: var(--spacing-lg);
}

.social-links a {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background-color: var(--color-primary);
  color: white;
  transition: background-color var(--transition-fast);
}

.social-links a:hover {
  background-color: var(--color-btn-hover);
}

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

.interests h3, .education h3 {
  margin-bottom: var(--spacing-md);
  font-size: var(--font-size-lg);
}

.education ul {
  list-style: none;
  padding: 0;
}

.education li {
  margin-bottom: var(--spacing-md);
}

.education .degree {
  display: block;
  font-weight: 700;
}

.education .institution {
  display: block;
  color: var(--color-secondary);
}

.education .year {
  display: block;
  font-size: var(--font-size-sm);
  color: var(--color-secondary);
}

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

/* Section styles */
section {
  padding: var(--spacing-2xl) 0;
}

.section-title {
  text-align: center;
  margin-bottom: var(--spacing-xl);
  position: relative;
}

.section-title::after {
  content: '';
  display: block;
  width: 50px;
  height: 3px;
  background-color: var(--color-primary);
  margin: var(--spacing-xs) auto 0;
}

/* Experience section */
.timeline {
  position: relative;
  max-width: 800px;
  margin: 0 auto;
}

.timeline::before {
  content: '';
  position: absolute;
  top: 0;
  bottom: 0;
  left: 20px;
  width: 2px;
  background-color: var(--color-timeline-bg);
}

.timeline-item {
  position: relative;
  padding-left: 50px;
  margin-bottom: var(--spacing-xl);
}

.timeline-marker {
  position: absolute;
  left: 0;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background-color: var(--color-timeline-marker);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  z-index: 1;
}

.timeline-content h3 {
  margin-bottom: var(--spacing-xs);
}

.timeline-info {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-md);
  color: var(--color-secondary);
  font-size: var(--font-size-sm);
}

/* Projects section */
.filter-buttons {
  display: flex;
  justify-content: center;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-xl);
}

.filter-btn {
  background: none;
  border: 2px solid var(--color-primary);
  color: var(--color-primary);
  padding: var(--spacing-xs) var(--spacing-md);
  border-radius: var(--radius-full);
  cursor: pointer;
  font-weight: 500;
  transition: background-color var(--transition-fast), color var(--transition-fast);
  font-size: var(--font-size-sm);
}

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

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

.project-card {
  background-color: var(--color-card-bg);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: 0 4px 10px var(--color-shadow);
  transition: transform var(--transition-normal), box-shadow var(--transition-normal);
  height: 100%;
  display: flex;
  flex-direction: column;
}

.project-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 20px var(--color-shadow);
}

.project-image {
  height: 180px;
  overflow: hidden;
}

.project-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform var(--transition-normal);
}

.project-card:hover .project-image img {
  transform: scale(1.05);
}

.project-content {
  padding: var(--spacing-md);
  flex-grow: 1;
  display: flex;
  flex-direction: column;
}

.project-content h3 {
  margin-bottom: var(--spacing-xs);
  font-size: var(--font-size-lg);
}

.project-content p {
  margin-bottom: var(--spacing-md);
  color: var(--color-secondary);
  font-size: var(--font-size-sm);
  flex-grow: 1;
}

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

/* Publications section */
.publication-card {
  display: flex;
  gap: var(--spacing-lg);
  background-color: var(--color-card-bg);
  border-radius: var(--radius-md);
  padding: var(--spacing-md);
  box-shadow: 0 4px 10px var(--color-shadow);
  margin-bottom: var(--spacing-lg);
}

.publication-image {
  flex-shrink: 0;
  width: 120px;
  height: 120px;
  overflow: hidden;
  border-radius: var(--radius-sm);
}

.publication-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.publication-content h3 {
  margin-bottom: var(--spacing-xs);
  font-size: var(--font-size-lg);
}

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

.publication-details {
  display: flex;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-md);
  font-size: var(--font-size-sm);
  color: var(--color-secondary);
}

.publication-abstract {
  margin-bottom: var(--spacing-md);
  font-size: var(--font-size-sm);
}

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

/* Talks section */
.talk-card {
  display: flex;
  gap: var(--spacing-lg);
  background-color: var(--color-card-bg);
  border-radius: var(--radius-md);
  padding: var(--spacing-md);
  box-shadow: 0 4px 10px var(--color-shadow);
  margin-bottom: var(--spacing-lg);
}

.talk-image {
  flex-shrink: 0;
  width: 120px;
  height: 120px;
  overflow: hidden;
  border-radius: var(--radius-sm);
}

.talk-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.talk-content h3 {
  margin-bottom: var(--spacing-xs);
  font-size: var(--font-size-lg);
}

.talk-details {
  display: flex;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-md);
  font-size: var(--font-size-sm);
  color: var(--color-secondary);
}

.talk-content p {
  font-size: var(--font-size-sm);
  margin-bottom: var(--spacing-md);
}

/* Blog section */
.blog-intro {
  max-width: 800px;
  margin: 0 auto var(--spacing-xl);
  text-align: center;
}

.blog-sample {
  background-color: var(--color-card-bg);
  border-radius: var(--radius-md);
  padding: var(--spacing-xl);
  box-shadow: 0 4px 10px var(--color-shadow);
  max-width: 800px;
  margin: 0 auto;
}

.blog-sample h3 {
  margin-bottom: var(--spacing-md);
}

.blog-sample h4 {
  margin-top: var(--spacing-lg);
  margin-bottom: var(--spacing-sm);
}

.math-block {
  padding: var(--spacing-md);
  background-color: var(--color-code-bg);
  border-radius: var(--radius-md);
  margin: var(--spacing-md) 0;
  overflow-x: auto;
}

/* Buttons */
.btn {
  display: inline-block;
  padding: var(--spacing-xs) var(--spacing-md);
  border-radius: var(--radius-sm);
  font-weight: 500;
  text-align: center;
  cursor: pointer;
  transition: background-color var(--transition-fast), color var(--transition-fast);
  font-size: var(--font-size-sm);
}

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

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

.btn-secondary {
  background-color: transparent;
  color: var(--color-primary);
  border: 1px solid var(--color-primary);
}

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

/* Footer */
footer {
  background-color: var(--color-footer-bg);
  padding: var(--spacing-lg) 0;
}

.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

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

.footer-links a {
  color: var(--color-text);
  font-size: var(--font-size-lg);
}

.footer-links a:hover {
  color: var(--color-primary);
}

/* Modal */
.modal {
  display: none;
  position: fixed;
  z-index: 2000;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.5);
  overflow: auto;
}

.modal-content {
  background-color: var(--color-card-bg);
  margin: 15% auto;
  padding: var(--spacing-xl);
  border-radius: var(--radius-md);
  max-width: 600px;
  position: relative;
}

.close {
  position: absolute;
  top: var(--spacing-md);
  right: var(--spacing-md);
  font-size: var(--font-size-2xl);
  cursor: pointer;
}

#citationText {
  background-color: var(--color-code-bg);
  padding: var(--spacing-md);
  border-radius: var(--radius-sm);
  margin: var(--spacing-md) 0;
  white-space: pre-wrap;
  font-family: var(--font-code);
  font-size: var(--font-size-sm);
}

/* Text center utility */
.text-center {
  text-align: center;
}

/* Media Queries */
@media (max-width: 992px) {
  .about-grid {
    grid-template-columns: 1fr;
    text-align: center;
  }
  
  .about-image {
    margin-bottom: var(--spacing-lg);
  }
  
  .about-details {
    grid-template-columns: 1fr;
  }
  
  .cta-buttons {
    justify-content: center;
  }
  
  .publication-card, .talk-card {
    flex-direction: column;
  }
  
  .publication-image, .talk-image {
    width: 100%;
    height: 180px;
    margin-bottom: var(--spacing-md);
  }
}

@media (max-width: 768px) {
  .nav-toggle {
    display: flex;
  }
  
  .nav-links {
    position: fixed;
    top: 60px;
    left: 0;
    width: 100%;
    flex-direction: column;
    background-color: var(--color-header-bg);
    padding: var(--spacing-lg) 0;
    box-shadow: 0 5px 10px var(--color-shadow);
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
    transition: transform var(--transition-normal), opacity var(--transition-normal);
  }
  
  .nav-links.active {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }
  
  .nav-links li {
    margin: var(--spacing-sm) 0;
  }
  
  .projects-grid {
    grid-template-columns: 1fr;
  }
  
  .footer-content {
    flex-direction: column;
    gap: var(--spacing-lg);
  }
}

@media (max-width: 576px) {
  :root {
    --font-size-base: 0.9rem;
  }
  
  .hero-image img {
    width: 150px;
    height: 150px;
  }
  
  .timeline-item {
    padding-left: 50px;
  }
  
  .timeline-marker {
    width: 30px;
    height: 30px;
  }
}

/* Print styles */
@media print {
  header, footer, .filter-buttons, .btn {
    display: none;
  }
  
  body {
    background-color: white;
    color: black;
  }
  
  main {
    padding-top: 0;
  }
  
  .container {
    max-width: 100%;
    padding: 0;
  }
  
  section {
    page-break-inside: avoid;
  }
}