<!DOCTYPE html>
<title>flexbox | flex formatting context :: float intrusion</title>
<link rel="author" href="http://opera.com" title="Opera Software">
<style>
* {margin: 0;}
#float {
	background: lightblue;
	width: 200px;
	float: left;
}
#flex {
	background: #ffcc00;
	margin-left: -200px;
	width: 400px;
	overflow: hidden;
}
div div {
	margin: 2em;
}
</style>

<div id="float">float</div>

<div id="flex">
	<div>Yellow box yellow box yellow box</div>
</div>