/* CSS Variables for theming */
:root {
  --primary-color: #2563eb;
  --secondary-color: #1e40af;
  --accent-color: #0ea5e9;

  --text-primary: #111827;
  --text-secondary: #6b7280;
  --text-light: #9ca3af;
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-tertiary: #f1f5f9;
  --border-color: #e5e7eb;
  --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);
  --border-radius: 0.5rem;
  --transition: all 0.3s ease;
}

/* Dark theme */
[data-theme="dark"] {
  --text-primary: #f9fafb;
  --text-secondary: #d1d5db;
  --text-light: #9ca3af;
  --bg-primary: #111827;
  --bg-secondary: #1f2937;
  --bg-tertiary: #374151;
  --border-color: #374151;
}

/* Reset and base styles */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--bg-primary);
  transition: var(--transition);
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.2;
  margin-bottom: 1rem;
}

h1 { font-size: 3rem; }
h2 { font-size: 2.25rem; }
h3 { font-size: 1.875rem; }
h4 { font-size: 1.5rem; }
h5 { font-size: 1.25rem; }
h6 { font-size: 1.125rem; }

p {
  margin-bottom: 1rem;
  color: var(--text-secondary);
  text-align: justify;
}

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

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

/* Header and Navigation */
.header {
  position: fixed;
  top: 0;
  width: 100%;
  background-color: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
  z-index: 1000;
  transition: var(--transition);
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 4rem;
}

.nav-logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
}

.nav-menu {
  display: flex;
  list-style: none;
  gap: 2rem;
}

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

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

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

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

.bar {
  width: 25px;
  height: 3px;
  background-color: var(--text-primary);
  margin: 3px 0;
  transition: 0.3s;
}

/* Main content */
.main {
  margin-top: 4rem;
  min-height: calc(100vh - 4rem);
}

/* Hero section */
.hero {
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
  padding: 6rem 0;
  text-align: center;
}

.hero-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

.hero-title {
  font-size: 3.5rem;
  font-weight: 700;
  margin-bottom: 1.5rem;
  background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--text-secondary);
  margin-bottom: 2rem;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.hero-cta {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  border-radius: var(--border-radius);
  font-weight: 500;
  text-decoration: none;
  transition: var(--transition);
  border: none;
  cursor: pointer;
}

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

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

.btn-outline {
  background-color: transparent;
  color: var(--primary-color);
  border: 2px solid var(--primary-color);
}

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

/* Sections */
.section {
  padding: 5rem 0;
}

.section-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

.section-title {
  text-align: center;
  margin-bottom: 3rem;
}

.section-subtitle {
  text-align: center;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 3rem;
}

/* Grid layouts */
.grid {
  display: grid;
  gap: 2rem;
}

.grid-2 {
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.grid-3 {
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
}

/* Cards */
.card {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: 2rem;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
}

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

.card-title {
  color: var(--text-primary);
  margin-bottom: 1rem;
}

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

/* Skills section */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 2rem;
  margin-top: 3rem;
}

.skill-category {
  background-color: var(--bg-secondary);
  padding: 2rem;
  border-radius: var(--border-radius);
  border: 1px solid var(--border-color);
}

.skill-category h3 {
  color: var(--primary-color);
  margin-bottom: 1rem;
}

.skill-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.skill-tag {
  background-color: var(--bg-tertiary);
  color: var(--text-secondary);
  padding: 0.25rem 0.75rem;
  border-radius: 1rem;
  font-size: 0.875rem;
  border: 1px solid var(--border-color);
}

/* Projects grid */
.projects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
  gap: 2rem;
  margin-top: 3rem;
}

.project-card {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  overflow: hidden;
  transition: var(--transition);
  box-shadow: var(--shadow-sm);
}

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

.project-header {
  padding: 1.5rem;
  border-bottom: 1px solid var(--border-color);
}

.project-title {
  margin-bottom: 0.5rem;
}

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

.project-content {
  padding: 1.5rem;
}

.project-description {
  margin-bottom: 1rem;
}

.project-tech {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
}

.tech-tag {
  background-color: var(--accent-color);
  color: white;
  padding: 0.25rem 0.5rem;
  border-radius: 0.25rem;
  font-size: 0.75rem;
  font-weight: 500;
}

.project-links {
  display: flex;
  gap: 1rem;
}

/* Publications */
.publication-item {
  background-color: var(--bg-secondary);
  padding: 2rem;
  border-radius: var(--border-radius);
  border-left: 4px solid var(--primary-color);
  margin-bottom: 2rem;
}

.publication-title {
  color: var(--text-primary);
  margin-bottom: 0.5rem;
}

.publication-authors {
  color: var(--text-secondary);
  font-style: italic;
  margin-bottom: 0.5rem;
}

.publication-venue {
  color: var(--primary-color);
  font-weight: 500;
}

/* Footer */
.footer {
  background-color: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 3rem 0 1rem;
  margin-top: auto;
}

.footer-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

.footer-content {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 2rem;
  margin-bottom: 2rem;
}

.footer-section h3,
.footer-section h4 {
  color: var(--text-primary);
  margin-bottom: 1rem;
}

.social-links {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.social-links a {
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: var(--transition);
}

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

.footer-bottom {
  text-align: center;
  padding-top: 2rem;
  border-top: 1px solid var(--border-color);
  color: var(--text-light);
}

/* Responsive design */
@media (max-width: 768px) {
  .nav-menu {
    position: fixed;
    left: -100%;
    top: 4rem;
    flex-direction: column;
    background-color: var(--bg-primary);
    width: 100%;
    text-align: center;
    transition: 0.3s;
    box-shadow: var(--shadow-lg);
    border-top: 1px solid var(--border-color);
    padding: 2rem 0;
  }

  .nav-menu.active {
    left: 0;
  }

  .nav-menu li {
    margin: 1rem 0;
  }

  .hamburger {
    display: flex;
  }

  .hamburger.active .bar:nth-child(2) {
    opacity: 0;
  }

  .hamburger.active .bar:nth-child(1) {
    transform: translateY(8px) rotate(45deg);
  }

  .hamburger.active .bar:nth-child(3) {
    transform: translateY(-8px) rotate(-45deg);
  }

  .hero-title {
    font-size: 2.5rem;
  }

  .hero-cta {
    flex-direction: column;
    align-items: center;
  }

  .btn {
    width: 100%;
    max-width: 300px;
    justify-content: center;
  }

  h1 { font-size: 2rem; }
  h2 { font-size: 1.75rem; }
  h3 { font-size: 1.5rem; }

  .projects-grid {
    grid-template-columns: 1fr;
  }

  .grid-2,
  .grid-3 {
    grid-template-columns: 1fr;
  }
}

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

.fade-in-up {
  animation: fadeInUp 0.6s ease-out;
}

/* Utility classes */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mt-1 { margin-top: 0.25rem; }
.mt-2 { margin-top: 0.5rem; }
.mt-3 { margin-top: 1rem; }
.mt-4 { margin-top: 1.5rem; }

.mb-1 { margin-bottom: 0.25rem; }
.mb-2 { margin-bottom: 0.5rem; }
.mb-3 { margin-bottom: 1rem; }
.mb-4 { margin-bottom: 1.5rem; } 

/* Theme Toggle Button */
.theme-toggle {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text-primary);
  transition: var(--transition);
  padding: 0.5rem;
  border-radius: var(--border-radius);
  display: flex;
  align-items: center;
  justify-content: center;
}

.theme-toggle:hover {
  color: var(--primary-color);
  background-color: var(--bg-secondary);
}

.theme-toggle .sun-icon,
.theme-toggle .moon-icon {
  display: none; /* Hidden by default */
}

/* Show sun icon in light mode */
html:not([data-theme="dark"]) .theme-toggle .sun-icon {
  display: block;
}

/* Show moon icon in dark mode */
html[data-theme="dark"] .theme-toggle .moon-icon {
  display: block;
}

/* Adjust hamburger position if needed for spacing */
@media (max-width: 768px) {
  .nav-container {
    justify-content: space-between; /* Ensure space between logo, menu, toggle, hamburger */
  }
  .theme-toggle {
    margin-right: 1rem; /* Space between toggle and hamburger */
  }
}

/* Blog Post Styles */
.blog-post {
  max-width: 800px;
  margin: 0 auto;
  padding: 2rem;
  background-color: var(--bg-primary);
  border-radius: var(--border-radius);
  box-shadow: var(--shadow-md);
}

.blog-post-title {
  font-size: 2.5rem;
  margin-bottom: 1rem;
  color: var(--text-primary);
  text-align: center;
}

.blog-post-meta {
  text-align: center;
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 2rem;
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.blog-post-meta span {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.blog-post-content {
  line-height: 1.8;
  color: var(--text-primary);
}

.blog-post-content h1,
.blog-post-content h2,
.blog-post-content h3,
.blog-post-content h4,
.blog-post-content h5,
.blog-post-content h6 {
  color: var(--primary-color);
  margin-top: 2rem;
  margin-bottom: 1rem;
}

.blog-post-content p {
  margin-bottom: 1rem;
  color: var(--text-secondary);
}

.blog-post-content ul,
.blog-post-content ol {
  margin-bottom: 1rem;
  padding-left: 1.5rem;
  color: var(--text-secondary);
}

.blog-post-content li {
  margin-bottom: 0.5rem;
}

.blog-post-content a {
  color: var(--accent-color);
  text-decoration: underline;
}

/* Blog Listing Styles */
.blog-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 2rem;
  margin-top: 3rem;
}

.blog-list-item {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius);
  padding: 2rem;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
  display: flex;
  flex-direction: column;
}

.blog-list-item:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.blog-list-title {
  font-size: 1.75rem;
  margin-bottom: 0.75rem;
}

.blog-list-title a {
  color: var(--text-primary);
  text-decoration: none;
}

.blog-list-title a:hover {
  color: var(--primary-color);
}

.blog-list-meta {
  color: var(--text-secondary);
  font-size: 0.85rem;
  margin-bottom: 1rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.blog-list-meta span {
  display: flex;
  align-items: center;
  gap: 0.3rem;
}

.blog-list-description {
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
  flex-grow: 1; /* Ensures cards are same height */
}

.tag {
  background-color: var(--accent-color);
  color: white;
  padding: 0.25rem 0.75rem;
  border-radius: 1rem;
  font-size: 0.75rem;
  font-weight: 500;
  display: inline-block;
  margin-right: 0.5rem;
  margin-bottom: 0.5rem;
}

.post-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}