JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>

  <head>

  	<style type="text/css">
  		.parent{
  			box-sizing: border-box;
  		}
  		.child{
  			height: 100px;
  			margin: 20px;
  			background: red;
  		}
  		.a1{
  			background: green;
  		}
  	</style>
  </head>

  <body>
    <div class="parent">
    	<div class="child"></div>
    	<div class="child a1"></div>
    </div>
  </body>

</html>