JSFiddle - React, Tailwind, and code Playground

HTML

<div>

</div>

CSS

html, body {
	height:100%;
	background: url("http://cs5-3.4pda.to/2271627.jpg");
}
div {
  width:35px;
  height: 35px;
  background: black;
  position:absolute;
}
div:after {
content: "";
position: relative;
width:0; height:0;
left: 100%;
top: 100%;
border-top: 35px solid black;
border-right: 35px solid transparent;
}