JSFiddle - React, Tailwind, and code Playground

HTML

<div id="menu">
    <ul>
        <li>linea 1</li>
        <li>linea 2</li>
    </ul>
    <span clasS="linguetta">mouse qui</span>
</div>

CSS

#menu {
    border: 1px #000 solid;
    position: absolute;
    top: 5em;
    width: 200px;
    margin-left: -150px;
}

#menu .linguetta {
    width: 50px;
    position: absolute;
    top: 0px;
    right: 0px;
}

#menu:hover {
    margin-left: 0;
}