JSFiddle - React, Tailwind, and code Playground

HTML

<div class="test"></div>

CSS

.test {
    position: absolute;
    left: 100px;
    top: 100px;
    width: 200px;
    height: 200px;
    background-color: lightblue;
}

.test:after {
    content: "";
    position: absolute;
    left: 0px;
    top: 0px;
    bottom: 0px; 
    right: 0px;
    box-shadow: 0px -10px 20px 10px black;
    clip: rect(-100px, 1000px, 100px, -100px);
}