JSFiddle - React, Tailwind, and code Playground

HTML

<div class="outer">
    <div class="inner"></div>
</div>

CSS

html, body {
    height: 100%;
}
.outer {
    height: 100%;
    width: 100%;
    background-color: yellow;
    position: relative;
}
.inner {
    width: 80%;
    height: 80%;    
    background-color: red;
    position: relative;
    top:0;
    bottom:0;
    right:0;
    left:0;    
}