body {
  max-width: 640px;
  margin: 2rem auto;
  padding: 0 1rem;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  line-height: 1.5;
  color: #111;
  background: #fff;
}

h1, h2, h3 {
  line-height: 1.2;
}

a {
  color: #0645ad;
}

footer {
  margin-top: 3rem;
  padding-top: 1rem;
  border-top: 1px solid #ddd;
  font-size: 0.9rem;
}

footer a {
  margin-right: 1rem;
}

hr {
  border: none;
  border-top: 1px solid #ddd;
  margin: 2rem 0;
}