JSFiddle - React, Tailwind, and code Playground

HTML

<div id="smth"></div>

CSS

html, body { height:100%; }

#smth {
    background-color: green;
    width: 200px;
    height: 50%;
    text-align: center;
    font-size: 100px;
}

#smth::before {
    display: block;
    content: "";
    height: 50%;
}

#smth::after {
    vertical-align: top;
    line-height: 0;
    content: "X";
    background-color: yellow;
}