Untitled

dabblet.css

.container
{
	position: absolute;
	top: 0;
	left: 0;
	width: 100%;
	height: 100%;
	text-align: center;
}

.container:before,
.box 
{
	display: inline-block;
	vertical-align: middle;
}

.container:before
{
	content: "";
	width: 0;
	margin-left: -10px;
	height: 100%;
}

.box 
{
	text-align: left;
	background: #333;
	width: 400px;
	height: 300px;
	border-radius: 1em;
	border: 1px solid #fff;
	background-clip: padding-box;
	position: relative;
	box-shadow: 0 0 5px rgba(0,0,0,.5);
}

.box:before
{
	content: "";
	display: block;
	position: absolute;
	width: 100%;
	height: 100%;
	z-index: -1;
	outline: 9999px solid rgba(0,0,0,.5);
	outline-offset: -5px;
}

dabblet.html

Text
<div class="container">
	<div class="box"></div>
</div>

settings.json

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