JSFiddle - React, Tailwind, and code Playground

HTML

<div id="test">
</div>

CSS

#test {
    background-color: #333;
    background-image: -webkit-linear-gradient(top, #333, #666);
    width: 100px;
    height: 100px;
    -webkit-transition: background 1s linear;
}

#test:hover {
    background-image: -webkit-linear-gradient(top, #666, #999);
}