body {
 max-width:650px;
 margin:40px auto;
 padding:0 10px;
 font:18px/1.5 sans;
 color:#444
}
h1,
h2,
h3 {
 line-height:1.2
}
@media (prefers-color-scheme: dark) {
 body {
  color:#c9d1d9;
  background:#0d1117
 }
 a:link {
  color:#58a6ff
 }
 a:visited {
  color:#8e96f0
 }
}