JSFiddle - React, Tailwind, and code Playground

by HDL52

HTML

<div id="triangle"></div>

CSS

body,
html {
  width: 100vw;
  height: 100vh;
  margin: 0;
  padding: 0;
  display: flex;
  justify-content: center;
  align-items: center;
}

#triangle {
  width: 100px;
  height: 100px;
  background: linear-gradient(
    45deg,
    red,
    red 50%,
    transparent 50%,
    transparent 100%
  );
}