body{font-family:system-ui,sans-serif;max-width:720px;margin:0 auto;padding:16px;color:#222;background:#fafafa;line-height:1.6}
header{border-bottom:1px solid #ddd;margin-bottom:24px}nav a{margin-right:12px;color:#0366d6}footer{margin-top:40px;color:#888;font-size:14px}