:root {
  /* Colors - Light Theme (Default) */
  --bg: #ffffff;
  --bg-alt: #f9fafb;
  --text: #1f2937;
  --text-light: #6b7280;
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --border: #e5e7eb;
  
  /* Typography */
  --font-sans: 'Roboto', -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  
  /* Spacing - Reduced for density */
  --spacing-sm: 0.35rem;
  --spacing-md: 0.75rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2.5rem;
  
  /* Layout */
  --container-width: 900px;
  --radius: 6px;
}

[data-theme="dark"] {
  --bg: #000000;
  --bg-alt: #111111;
  --text: #f9fafb;
  --text-light: #9ca3af;
  --primary: #60a5fa;
  --primary-hover: #93c5fd;
  --border: #374151;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg);
  color: var(--text);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  font-size: 15px;
  transition: background-color 0.3s, color 0.3s;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: color 0.2s;
}

a:hover {
  color: var(--primary-hover);
  text-decoration: underline;
}

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

/* Layout */
.container {
  width: 100%;
  max-width: var(--container-width);
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

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

.section.alt {
  background-color: var(--bg-alt);
  transition: background-color 0.3s;
}

/* Typography Helpers */
h1, h2, h3 {
  color: var(--text);
  line-height: 1.2;
  margin-bottom: var(--spacing-md);
}

h1 { font-size: 2rem; font-weight: 700; }
h2 { font-size: 1.5rem; font-weight: 600; }
h3 { font-size: 1.125rem; font-weight: 600; }

.eyebrow {
  text-transform: uppercase;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-light);
  margin-bottom: var(--spacing-sm);
  letter-spacing: 0.05em;
}

.lead {
  font-size: 1.1rem;
  color: var(--text-light);
  margin-bottom: var(--spacing-lg);
  max-width: 65ch;
}

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

/* Header */
.site-header {
  position: sticky;
  top: 0;
  background-color: var(--bg); /* Fallback */
  background-color: rgba(var(--bg-rgb), 0.95); /* We need RGB var for alpha, simplifying to just bg for now or specific alpha handling */
  /* For simplicity in this robust minimal setup, we'll use solid background matching theme or slightly transparent if we had rgb vars */
  background-color: var(--bg);
  border-bottom: 1px solid var(--border);
  z-index: 100;
  padding: var(--spacing-md) 0;
  transition: background-color 0.3s, border-color 0.3s;
}

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

.brand {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text);
}

.nav {
  display: flex;
  gap: var(--spacing-lg);
  align-items: center;
}

.nav a {
  color: var(--text-light);
  font-size: 0.9rem;
  font-weight: 500;
  text-decoration: none;
}

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

/* CV Button in Nav */
.nav .btn-cv {
  padding: 0.35rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  font-weight: 500;
  transition: all 0.2s;
}

.nav .btn-cv:hover {
  background-color: var(--primary);
  color: white;
  border-color: var(--primary);
  text-decoration: none;
}

/* Theme Toggle */
.theme-toggle {
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-light);
  padding: 4px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: color 0.2s;
}

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

/* Hero Section */
.hero-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-lg);
  align-items: center;
}

@media (min-width: 768px) {
  .hero-grid {
    grid-template-columns: 3fr 1.5fr;
  }
}

.details {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-lg);
  font-size: 0.9rem;
  color: var(--text-light);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.5rem 1rem;
  border-radius: var(--radius);
  font-weight: 500;
  text-decoration: none;
  font-size: 0.9rem;
  transition: all 0.2s;
}

.btn.primary {
  background-color: var(--primary);
  color: white; /* Keep white for contrast on primary button even in dark mode usually */
}

/* Ensure text on primary button is readable in dark mode if primary color is light */
[data-theme="dark"] .btn.primary {
  color: #000000;
}

.btn.primary:hover {
  background-color: var(--primary-hover);
  text-decoration: none;
}

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

.btn.ghost:hover {
  border-color: var(--text-light);
  text-decoration: none;
}

/* Profile Image */
.portrait-frame {
  aspect-ratio: 1;
  background-color: var(--bg-alt);
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--border);
  max-width: 250px;
  margin-left: auto;
  transition: border-color 0.3s, background-color 0.3s;
}

.portrait-frame img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* Cards (Research) */
.card-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-md);
  margin-top: var(--spacing-md);
}

@media (min-width: 768px) {
  .card-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

.card {
  padding: var(--spacing-md);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--bg);
  transition: transform 0.2s, box-shadow 0.2s, background-color 0.3s, border-color 0.3s;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 5px 10px -3px rgba(0, 0, 0, 0.05);
}

.card h3 {
  margin-bottom: var(--spacing-sm);
  font-size: 1rem;
}

.card p {
  font-size: 0.9rem;
  color: var(--text);
  margin-bottom: var(--spacing-sm);
}

.meta {
  margin-top: var(--spacing-sm);
  font-size: 0.8rem;
  color: var(--text-light);
  border-top: 1px solid var(--border);
  padding-top: var(--spacing-sm);
}

/* Publications */
.pub-list {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
  margin-top: var(--spacing-md);
}

.pub {
  padding-left: var(--spacing-md);
  border-left: 2px solid var(--border);
  transition: border-color 0.3s;
}

.pub-title {
  font-weight: 600;
  font-size: 1rem;
  margin-bottom: 0.1rem;
}

.pub-meta {
  font-size: 0.85rem;
  color: var(--text-light);
  margin-bottom: 0.25rem;
}

.pub-summary {
  font-size: 0.9rem;
}

/* Contact Compact */
.compact-contact {
  display: flex;
  gap: var(--spacing-sm);
  flex-wrap: wrap;
  align-items: center;
  font-size: 1rem;
}

.compact-contact .sep {
  color: var(--border);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border);
  padding: var(--spacing-lg) 0;
  margin-top: var(--spacing-xl);
  color: var(--text-light);
  font-size: 0.85rem;
  transition: border-color 0.3s;
}

.footer-content {
  display: flex;
  justify-content: center; /* Centered content */
  align-items: center;
}

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

/* Mobile */
@media (max-width: 640px) {
  .header-bar {
    flex-direction: column;
    gap: var(--spacing-sm);
  }
  
  .nav {
    gap: var(--spacing-md);
    font-size: 0.85rem;
  }
  
  .portrait-frame {
    margin: 0 auto;
    max-width: 200px;
  }
}