JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="box">
    </div>
</div>

CSS

body {
        margin: 0px
    }
    .container {
        width: 100vw;
        height: 100vh;
        background: #6C7A89;
        display: flex;
        flex-direction: row;
        justify-content: center;
        align-items: center
    }
    .box {
        width: 300px;
        height: 300px;
        background: #fff;
    }