JSFiddle - React, Tailwind, and code Playground

HTML

<div class="d1">
    <div class="d2"></div>
</div>

CSS

.d1 {
    background: blue;
    width: 600px;
    height: 400px;
}
.d2 {
    background: yellow;
    width: 300px;
    height: 100px;
    margin: 0 auto;
}