JSFiddle - React, Tailwind, and code Playground

HTML

<div class="content-wrapper">
    <div class="popup">
        <div class="close">
        </div>
    </div>
</div>

CSS

.popup, .close { position: absolute; height: 200px; width: 200px; }
.popup { background: #f00; }
.close { background: #ff0; top: 25px; left: 25px; z-index: -1; }