body {
  font-family: system-ui, sans-serif;
  background: #111;
  color: #f5f5f5;
  margin: 0;
  padding: 2em;
}
a { color: #33aaff; text-decoration: none; }
a:hover { text-decoration: underline; }
header, footer { text-align: center; margin-bottom: 2em; }