JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="fixed-block"></div>
</div>

CSS

.container {
    transform: translate(0, 50px);
    height: 100px;
    background-color: #ccc;
}

.fixed-block {
    position: fixed;
    left: 0;
    top: 0;
    width: 200px;
    height: 200px;
    background-color: #333;
}