JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

* {
  box-sizing: border-box
}


div {
  width: 100px;
  height: 100px;
  border: 1px dotted gray;
  background: radial-gradient(at top left, gray 11px, red 12px, red 14px, transparent 15px) no-repeat right bottom / 15px 15px;
}