Vertical centering - Viewport unit method

dabblet.css

/**
 * Vertical centering - Viewport unit method
 */

main {
	width: 18em;
	padding: 1em 1.5em;
	margin: 50vh auto 0;
	transform: translateY(-50%);
	box-sizing: border-box;
	background: #655;
	color: white;
	text-align: center;
}

h1 {
	margin: 0 0 .2em;
	font-size: 150%;
}

p {
	margin: 0;
}

body {
	background: #fb3;
	font: 100%/1.5 sans-serif;
}

dabblet.html

<main>
	<h1>Am I centered yet?</h1>
	<p>Center me, please!</p>
</main>

dabblet.js

// alert('Hello world!');

settings.json

{"view":"split-vertical","fontsize":"100","seethrough":"","prefixfree":"1","page":"css"}