JSFiddle - React, Tailwind, and code Playground

by cathead

HTML

<div>erferf</div>

CSS

div{
    position:relative;
    background: #444;
    padding: 10px;
}    

div:after{
    content: '';
    position: absolute;
    z-index: -1;            /*  <= not working:( */
    background: #3d3;
    left: 20px;
    top: 20px; 
    width: 30px;
    height: 30px;
}