JSFiddle - React, Tailwind, and code Playground

HTML

<div id="triangle" />

CSS

#triangle {
    background: purple;
    width :150px;
    height:150PX;
    border-left: 50px solid black ;
    border-right: 50px solid black;
    border-bottom: 50px solid black;
    border-top: 50px solid black;
}