<!DOCTYPE html>
<html>
<head>
<title>video-with-alpha</title>
<style>
body {
background: white;
}
#spacer {
position: absolute;
left: 200px;
top: 0px;
width: 200px;
height: 200px;
background-color: red;
</style>
</head>
<body>
<div id="spacer"></div>
</body>
</html>