body {
  font-family: system-ui, sans-serif;
  line-height: 1.5;
  max-width: 42rem;
  margin: 2rem auto;
  padding: 0 1rem;
  color: #1a1a1a;
  background: #f6f7f9;
}
main { background: #fff; padding: 1.5rem; border-radius: 8px; }
a { color: #2563eb; }
nav a { margin-right: 1rem; }