JSFiddle - React, Tailwind, and code Playground

by Alexey Mishin

HTML

<div id="shadow">12</div>

CSS

#shadow {
  position: relative;
  width: 400px;
  height: 400px;
  margin: 40px auto;
  
  background-color: lightgrey;
}

#shadow::before {
  box-shadow: -13px 0 10px -13px inset;
  content: " ";
  height: 100%;
  left: -15px;
  position: absolute;
  width: 15px;
}

#shadow::after {
  position: absolute;
  height: 100%;
  width: 13px;
  right: -15px;
  content: "";
  box-shadow: -13px 0 
}