JSFiddle - React, Tailwind, and code Playground

HTML

<div id="someid" class="window">
   <div id="loader"></div>
</div>

CSS

.window{
    height:400px;
    width:400px;
    background:red;
    vertical-align:middle;
    line-height:400px;
    text-align:center;
}
#loader{
    width:20px;
    height:20px;
    background:green;
    display:inline-block;
    vertical-align:middle;
}