Black Light

<div></div>
<style>
  body {
    background: #5776f6;
    margin: 100px 0;
  }
  div {
    width: 0;
    height: 50px;
    border-bottom: 25px solid #5776f6;
    border-top: 25px solid #5776f6;
    border-right: 400px solid #191919;
  }
</style>