JSFiddle - React, Tailwind, and code Playground

HTML

<div id="wrapper">
<div id="fixed"></div>
</div>

CSS

#wrapper {
    width: 400px;
    height: 600px;
    margin: 0 auto;
    background-color: lightblue;
}
#fixed {
    width: 40px;
    height: 100px;
    position: fixed;
    top: 0;
    margin-left: 400px;
    background-color: darkblue;
}