JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container"><div class="outer"></div></div>

CSS

#container {
margin: 0 auto;
width: 200px;
    height: 40px;
    background-color: #777;
}
#container .outer {
         position: absolute;
        left: 0;
    right: 0;
    height: 30px;
    background-color: #999;
}