:root {
  --primary: #1a1a1a;
  --accent: #004d40;
  --bg: #ffffff;
  --text: #333;
  --muted: #666;
}

* {
  box-sizing: border-box;
}

body {
  font-family: 'Georgia', serif;
  line-height: 1.6;
  color: var(--text);
  margin: 0;
  padding: 0;
}

header {
  border-bottom: 2px solid var(--primary);
  padding: 1rem 0;
  background: var(--bg);
}

.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 0 1rem;
}

nav ul {
  list-style: none;
  padding: 0;
  display: flex;
  gap: 1.5rem;
}

nav a {
  text-decoration: none;
  color: var(--primary);
  font-weight: bold;
}

nav a:hover {
  text-decoration: underline;
}

h1, h2, h3 {
  font-family: 'Helvetica Neue', Arial, sans-serif;
  color: var(--primary);
  margin-top: 2rem;
}

h1 { font-size: 2.5rem; }
h2 { font-size: 1.8rem; border-bottom: 1px solid #ddd; padding-bottom: 0.5rem; }

section {
  margin-bottom: 3rem;
}

.phenomena-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
}

.phenomena-table th, .phenomena-table td {
  border: 1px solid #ddd;
  padding: 0.75rem;
  text-align: left;
}

.phenomena-table th {
  background-color: #f8f9fa;
  font-weight: bold;
}

footer {
  background: #f4f4f4;
  padding: 2rem 0;
  margin-top: 4rem;
  border-top: 1px solid #ddd;
  font-size: 0.9rem;
}

.footer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 2rem;
}

.citation {
  font-size: 0.9rem;
  color: var(--muted);
  border-left: 3px solid var(--accent);
  padding-left: 1rem;
  margin: 1rem 0;
}

.btn {
  display: inline-block;
  background: var(--primary);
  color: #fff;
  padding: 0.5rem 1rem;
  text-decoration: none;
  border-radius: 4px;
}

.btn:hover {
  background: var(--accent);
}

@media (max-width: 768px) {
  nav ul { flex-direction: column; gap: 0.5rem; }
  h1 { font-size: 2rem; }
}