Beispiel:SELFHTML-Beispiel-Grundlayout.css

/* Grundlayout für SELFHTML-Beispiele */
html {
	background: transparent!important;
  --blue: #337599;
  --green: #93b946;
  --red: #c82f04;
  --yellow: #dfac20;
  --lightblue: #d6e3eb;
  --lightgreen: #ebf5d7; 
  --lightred: #ffebe6;
  --lightyellow: #f9eed2;
}

body {
	margin: 1em auto;
	max-width: 60em;
	font-family: sans-serif;
	color: #333333;
}

h1  {
	font-size: 1.5rem;
	position: relative;
	padding-left: 3em;
}

h1:before {
	position: absolute;
	left: 0;
	content: "";
	width: 2rem;
	border:thin solid transparent;
	aspect-ratio: 1/1;
	background: url("https://wiki.selfhtml.org/images/4/45/SELF-Logo.svg") no-repeat;
	background-size: cover;
}