body {
  max-width: 900px;
  margin: 48px auto;
  padding: 0 20px;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial;
  line-height: 1.6;
  color: #111;
}

header {
  margin-bottom: 40px;
}

nav a {
  margin-right: 18px;
  text-decoration: none;
  color: #0366d6;
  font-weight: 500;
}

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

h1 {
  margin-bottom: 0;
}

h2 {
  margin-top: 36px;
}

footer {
  margin-top: 60px;
  font-size: 0.9em;
  color: #555;
}