JSFiddle - React, Tailwind, and code Playground

HTML

<div class="center">
    <div class="main"></div>
</div>

CSS

.center {    
    background: rgba(85, 85, 85, 0.5);
    height:200px;
    width:100px;
}

.main {
    background: #222;
    height: 100px;
    width: 50px;
    margin: 0 auto;
}