JSFiddle - React, Tailwind, and code Playground

HTML

<div id="test"></div>
<div id="test2"></div>

CSS

#test {
    background: rgba( 0, 0, 0, 0.8 );
    width: 200px; height: 200px;
}

#test2 {
    background: #333;
    width: 200px; height: 200px;
}