body {
  font-family: 'SF Mono', monospace;
  line-height: 1.6;
  max-width: 800px;
  margin: 0 auto;
  padding: 20px;
}
header {
  border-bottom: 2px solid #ddd;
  margin-bottom: 30px;
}
h1, h2, h3 {
  color:#333;
}
footer {
  border-top: 1px solid #ddd;
  margin-top: 30px;
  text-align: center;
}