JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container-box">
   <div class="overlay-box">Some content</div>
</div>

CSS

.container-box {
   background-color:#000;
   width:100%;
   height: 100%;
   text-align:center;
}
.overlay-box {
   background-color:#fff;
   width:300px;
   margin: auto;
}