JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <div class="other_things"></div>
    <div id="full"></div>
    
</body>

CSS

body { position: relative; }

#full {
    background: rgba(0,0,0,.6);
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
}
.other_things {width:40em; height: 50em;}