JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

div {
    width: 200px;
    height: 200px;
    margin: auto;
    background: black;
}

div:before {
    content: "";
    position: absolute;
    top: 0;
    left: 0;
    width: 100px;
    height: 100px;
    background-color: red;
}

div:after {
    content: " ";
    position: absolute;
    top: 0;
    left: auto;
    right: 0;
    width: 100px;
    height: 100px;
    background-color: blue;
}