JSFiddle - React, Tailwind, and code Playground

HTML

<html>
    <head></head>
    <body>
        <iframe title="YouTube video player" frameborder="0" allowfullscreen="true" allowtransparency="true" width="100%" height="100%" src="http://www.youtube.com/embed/FOHJUrcVdJk?wmode=opaque"></iframe>
        <div>This should overlap the video.</div>
    </body>
</html>

CSS

iframe
{
    position: absolute;
}

div
{
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
    background-color: #7f7f7f;
}