:root {
  /* Color Palette - Light Theme */
  --color-primary: #464A4E;
  /* Grijs1 - Main Text/UI */
  --color-secondary: #919BA0;
  /* Grijs2 - Secondary Text/Borders */
  --color-accent: #0E1F8C;
  /* Blauw  - Highlights/Hover */

  --color-bg: #ffffff;
  --color-bg-card: #ffffff;
  --color-text: #464A4E;
  --color-text-muted: #919BA0;

  /* Typography */
  --font-main: 'Inter', system-ui, -apple-system, sans-serif;
  --font-display: 'Outfit', sans-serif;

  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 2rem;
  --spacing-lg: 4rem;
  --spacing-xl: 6rem;

  /* Layout */
  --max-width: 1200px;
  --nav-height: 80px;
}

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

body {
  background-color: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-main);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

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

a {
  color: inherit;
  text-decoration: none;
  transition: color 0.3s ease;
}

ul {
  list-style: none;
}

/* Utilities */
.container {
  width: 90%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-sm);
}

.btn {
  display: inline-block;
  padding: 0.8rem 1.5rem;
  border-radius: 4px;
  font-weight: 600;
  letter-spacing: 0.5px;
  text-transform: uppercase;
  font-size: 0.9rem;
  transition: all 0.3s ease;
  border: 1px solid transparent;
  cursor: pointer;
}

.btn-primary {
  background-color: var(--color-accent);
  color: #fff;
  box-shadow: 0 4px 10px rgba(14, 31, 140, 0.2);
}

.btn-primary:hover {
  background-color: #0b1a75;
  transform: translateY(-2px);
  box-shadow: 0 6px 15px rgba(14, 31, 140, 0.3);
}

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

.btn-outline:hover {
  background-color: var(--color-primary);
  color: #fff;
  transform: translateY(-2px);
}

/* Navigation */
.navbar {
  height: var(--nav-height);
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  z-index: 1000;
  border-bottom: 1px solid rgba(0, 0, 0, 0.05);
  transition: all 0.3s ease;
}

.nav-container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 100%;
}

.logo {
  font-family: var(--font-display);
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: -0.5px;
  color: var(--color-primary);
}

.logo span {
  color: var(--color-accent);
}

/* Nav Links - Hover Effect inspired by topology.fyi */
.nav-links {
  display: flex;
  gap: var(--spacing-md);
  align-items: center;
}

.nav-link {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--color-secondary);
  position: relative;
  transition: color 160ms ease-out;
}

.nav-link:hover,
.nav-link.active {
  color: var(--color-accent);
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--color-accent);
  transition: width 160ms ease-out;
  border-radius: 2px;
}

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

/* Mobile Nav Toggle */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  flex-direction: column;
  gap: 5px;
}

.nav-toggle span {
  display: block;
  width: 25px;
  height: 2px;
  background-color: var(--color-primary);
  transition: all 0.3s ease;
}

/* Hero Section */
.hero {
  min-height: 80vh;
  display: flex;
  align-items: center;
  padding-top: var(--nav-height);
  position: relative;
}

.hero-content {
  position: relative;
  z-index: 2;
  max-width: 800px;
}

.hero-title {
  font-size: 4rem;
  margin-bottom: var(--spacing-sm);
  color: var(--color-primary);
}

.hero-subtitle {
  font-size: 1.5rem;
  color: var(--color-secondary);
  margin-bottom: var(--spacing-md);
  max-width: 600px;
  font-weight: 300;
}

.hero-buttons {
  display: flex;
  gap: var(--spacing-sm);
}

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

.section-header {
  margin-bottom: var(--spacing-lg);
  position: relative;
  padding-left: var(--spacing-sm);
  border-left: 4px solid var(--color-accent);
}

.section-title {
  font-size: 3rem;
  color: var(--color-primary);
  margin: 0;
}

/* Grid Layouts */
.grid {
  display: grid;
  gap: var(--spacing-md);
}

.grid-3 {
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.grid-2 {
  grid-template-columns: repeat(auto-fit, minmax(400px, 1fr));
}

/* Cards */
.card {
  background: var(--color-bg-card);
  border: 1px solid rgba(0, 0, 0, 0.08);
  /* Subtle grey border */
  padding: var(--spacing-md);
  border-radius: 8px;
  transition: transform 0.3s ease, box-shadow 0.3s ease, border-color 0.3s ease;
}

.card:hover {
  transform: translateY(-5px);
  border-color: var(--color-accent);
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.05);
}

.card-title {
  font-size: 1.25rem;
  color: var(--color-primary);
  margin-bottom: var(--spacing-xs);
}

.card-subtitle {
  font-size: 0.9rem;
  color: var(--color-secondary);
  margin-bottom: var(--spacing-sm);
  text-transform: uppercase;
  letter-spacing: 1px;
  font-weight: 600;
}

.card-text {
  color: var(--color-text);
  font-size: 1rem;
  font-weight: 300;
}

/* Publications */
.pub-item {
  padding: 1.5rem 0;
  border-bottom: 1px solid rgba(0, 0, 0, 0.05);
}

.pub-title {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
  color: var(--color-primary);
}

.pub-authors {
  color: var(--color-secondary);
  font-size: 0.95rem;
  margin-bottom: 0.5rem;
}

.pub-tag {
  background: rgba(14, 31, 140, 0.05);
  padding: 0.2rem 0.6rem;
  border-radius: 4px;
  color: var(--color-accent);
  font-size: 0.8rem;
  font-weight: 500;
}

/* Footer */
footer {
  background: #f8f9fa;
  /* Very light grey for footer */
  padding: var(--spacing-lg) 0;
  border-top: 1px solid rgba(0, 0, 0, 0.05);
  margin-top: var(--spacing-xl);
}

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

.footer-logo {
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: var(--spacing-xs);
  color: var(--color-primary);
}

.footer-text {
  color: var(--color-secondary);
  font-size: 0.9rem;
}

/* Responsive */
@media (max-width: 768px) {
  .hero-title {
    font-size: 2.5rem;
  }

  .nav-toggle {
    display: flex;
  }

  .nav-links {
    position: absolute;
    top: var(--nav-height);
    left: 0;
    width: 100%;
    background: #fff;
    flex-direction: column;
    padding: var(--spacing-md);
    gap: var(--spacing-sm);
    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
    transform: translateY(-150%);
    /* Hide by sliding up */
    transition: transform 0.3s ease;
    z-index: 999;
    align-items: flex-start;
  }

  .nav-links.active {
    transform: translateY(0);
    /* Slide down */
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.05);
  }

  .nav-link {
    font-size: 1.1rem;
    display: block;
    width: 100%;
    padding: 0.5rem 0;
  }

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

  /* Pubs on mobile */
  .pub-meta {
    flex-direction: column;
    gap: 0.5rem;
    align-items: flex-start;
  }
}

/* Team Photos & Avatars */
.team-card {
  text-align: center;
  padding-top: var(--spacing-md);
}

.member-photo {
  width: 150px;
  height: 150px;
  border-radius: 50%;
  margin: 0 auto var(--spacing-sm);
  background-size: cover;
  background-position: center;
  background-position: center;
}

.member-placeholder {
  width: 150px;
  height: 150px;
  border-radius: 50%;
  margin: 0 auto var(--spacing-sm);
  background-color: #f0f2f5;
  color: var(--color-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2rem;
  font-weight: 700;
  border: 3px solid rgba(0, 0, 0, 0.05);
}

.alumni-item {
  padding: 1rem;
  background: #f8f9fa;
  border-radius: 6px;
  font-size: 0.95rem;
}