JSFiddle - React, Tailwind, and code Playground

by Horia-Adrian Ionescu

HTML

<div class="aaa">
  <div class="bbb">
  
  </div>
</div>

CSS

.aaa{
  position:relative;
  background-color:red;
  height:100px;
  width:100px;
  border-top: 10px solid black;
  box-sizing: border-box;
}
.bbb{
  position:absolute;
  width:10px;
  height:10px;
  background-color: blue;
  top:10px;
}