JSFiddle - React, Tailwind, and code Playground

HTML

<div id="menu" class="menu">
    MENU
</div>
<div class="resto">
    RESTO DO CONTEUDO
</div>

CSS

.menu{width: 250px; float: left; position:blocked; background-color: blue}
.resto{background-color:#ccc;width:100%; float:right;}