JSFiddle - React, Tailwind, and code Playground
HTML
<div class="outer">I'm partially hidden. Change the opacity of fade to a higher value to prove it
<div class="inner">testing testing</div>
<div class="fade"></div>
</div>
CSS
.outer { position: relative; z-index: 2; }
.inner { background: #fff; left: 50px; position: fixed; top: 40px; z-index: 4; }
.fade { background: #555; bottom: 0; left: 0; opacity: 0.5; position: fixed; right: 0; top: 0; z-index: 3; }