<!DOCTYPE html>
<title>flexbox | margin: auto in overflow</title>
<link rel="author" href="http://opera.com" title="Opera Software">
<style>
div {
	background: blue;
	margin: 1em 0;
	border: 1px solid black;
	height: 8em;
	width: 32em;
	position: relative;
}
span {
	background: white;
	margin: 0;
	width: 12em;
	height: 6em;
	position: absolute;
	left: 0;
	top: 1em;
	display: inline-block;
}
span+span {
	background: yellow;
	width: 30em;
	left: 12em;
}
</style>

<div>
	<span>one</span>
	<span>two</span>
</div>