JSFiddle - React, Tailwind, and code Playground
by omvaity
HTML
<div class="box"></div>CSS
.box{width:100px;height:100px;background:#1D005D;position:relative;overflow:hidden;}
.box:after{background: #fff none repeat scroll 0 0;
border-radius: 20px;
content: " ";
display: block;
height: 20px;
left: -5px;
position: absolute;
top: -5px;
width: 20px;}
</style>