JSFiddle - React, Tailwind, and code Playground

HTML

<iframe class="youtube-player" type="text/html" width="520" height="330" src="http://www.youtube.com/embed/NWHfY_lvKIQ" frameborder="0"></iframe>
<div id="overlay">overlay</div>

CSS

#overlay {
    position:fixed;
    top:0;
    left:0;
    width:100%;
    height:100%;
    background:#000;
    opacity:0.5;
    /*background:rgba(255,255,255,0.8); or just this*/
    z-index:50;
    color:#fff;
}