JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

* {
  box-sizing: inherit;
}

html {
  box-sizing: border-box;
}
body {
  margin: 0;
}

div {
  width: 300px;
  height: 400px;
  margin: 40px auto;
    background:  linear-gradient(-45deg, gray 52%, transparent 52.1%),linear-gradient(35deg, red 25%, transparent 25.1%);

}