.content {
  max-width: 500px;
  margin: auto;
}

body {
  font-family: Arial, sans-serif;
  margin: 2em;
  background: #f9f9f9;
  color: #222;
}
header {
  border-bottom: 1px solid #ccc;
  margin-bottom: 2em;
}
h1 {
  margin: 0;
  font-size: 2em;
}
section {
  margin-bottom: 2em;
}
code,
pre {
  background: #eee;
  padding: 0.2em 0.4em;
  border-radius: 3px;
}