body {
	margin:1em auto;
	max-width:40em;
	padding:0 .62em;
	font:1.2em/1.62 Hack;
}

h1, h2, h3 {
	line-height:1.2;
}

@media print {
	body {
		max-width:none
	}
}

body {
	margin:1em auto;
	max-width:40em;
	padding:0 .62em;
	font:1.2em/1.62 Hack;
	linear-gradient(141deg, #0fb8ad 0%, #1fc8db 51%, #2cb5e8 75%)
}

h1, h2, h3 {
	line-height:1.2;
	border-bottom: 1px solid black;
}

h1 {
	border-bottom: 2px solid black;
	/* This overrides the 1px bottom border from previous section */
}

@media print {
	body {
		max-width:none
	}
}

Add background, add underline to headings.
Add background, add underline to headings.