JSFiddle - React, Tailwind, and code Playground

HTML

<div>&nbsp;</div>

SCSS

html, body { height: 100% }

$mobile: @media screen and (max-width: 300px);

div {
    width: 100%;
    height: 100%;
    background: red;
    
    $mobile {
        & {
            background: blue;    }
    }
}