.video-btn {
	background: #333;
	width: 20%;
	height: 20%;
	left: 50%;
	top: 50%;
	margin-top: -30px;
	margin-left: -30px;
	border-radius: 50px;
}

.video-btn::before {
	content: "";
	position: absolute;
	left: 50%;
	top: 50%;
	width: 0;
	height: 0;
	margin-top: -15.5px;
	margin-left: -11px;
	border-top: 15px solid transparent;
	border-bottom: 15px solid transparent;
	border-left: 28px solid #FFF;
}

Uses CSS3 attributes and psuedo elements to create a simple play button for web interfaces.

Simple CSS3 Play Button

video, button, CSS3

CSS