:root { color-scheme: light dark; }
* { box-sizing: border-box; }
body {
  margin: 0; font: 16px/1.5 system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  padding: 24px; max-width: 900px; margin-inline: auto;
}
header { margin-bottom: 24px; }
h1 { margin: 0 0 8px; }
nav a { text-decoration: none; margin-right: .5rem; opacity: .8; }
nav a:hover { opacity: 1; text-decoration: underline; }
main { padding: 16px 0; border-top: 1px solid #ddd; border-bottom: 1px solid #ddd; }
footer { margin-top: 24px; opacity: .7; }