JSFiddle - React, Tailwind, and code Playground

HTML

<div id="left">
</div>
<div id="right">
</div>

CSS

html, body {
    height: 100%;
}

#left {
    width:200px;
    float:left;
    background: #f00;
    height: 100%;
}
#right {
    float: left;
    background: #0f0;
    height: 100%;
    width: calc(100% - 200px);
}