/* Parent element can be any width and height */ 
.parent{
	position: fixed;
	width: 100%; /* can be any width */
	height: 100%;
	left: 0;
	top: 0;
	display: none;
	text-align: center;
}

.parent:before{ /* pseudo element to force vertical centering of child element */
	content: '';
	display: inline-block;
	height: 100%;
	vertical-align: middle;
}

.parent:after{ /* pseudo element to create overlay */
	background: black;
	content: '';
	position: absolute;
	width: 100%;
	height: 100%;
	top: 0;
	left: 0;
	opacity: 0.5;
	z-index: 10;
}

/* Centered child element can be any width and height */ 
.centeredchild{
	position: relative; /* position element to participate in z-indexing */
	z-index: 20; /* higher z-index than overlay */
	display: inline-block;
	vertical-align: middle;
	width: 80%; /* can be any width */
}

/* Video container to maintain Youtube 16:9 aspect ratio */ 
.videowrapper{
	position: relative;
	padding-top: 25px;
	padding-bottom: 56.25%; /* 16:9 aspect ratio */
	height: 0;
}

/* Make Youtube IFRAME responsive */ 
.videowrapper iframe {
	position: absolute;
	top: 0;
	left: 0;
	width: 100%;
	height: 100%;
}