JSFiddle - React, Tailwind, and code Playground

by Vitaliy

HTML

<div class="bg">
  <span class="btn"></span>
</div>

CSS

*{box-sizing:border-box;}
.bg{
  background:#333;
  width:300px;
  height:200px;
  position:relative;
}
.btn{
  position:absolute;
  display:block;
  width:90px;
  height:80px;
  top:50%;
  left:50%;
  margin-top:-40px;
  margin-left:-45px;
  background:transparent;
  border:5px solid rgba(200, 200, 200, .3);
  border-radius:10px;
}
.btn:after{
  content:"";
  display:block;
  position:absolute;
  border:20px solid transparent;
  border-left-color:rgba(200, 200, 200, .3);
  top:50%;
  left:50%;
  margin-top:-20px;
  margin-left:-8px;
}