JSFiddle - React, Tailwind, and code Playground

HTML

<iframe src="data:text/html,<!doctype html>
<html>
<style>
@media (min-width: 200px) {
  body { color: blue; text-align: right }
  @media (min-width: 300px) { 
    body { border: 5px solid }
  }
}
</style>
<p>Hello</p>
</html>
"></iframe>

CSS

iframe {
  animation: width 2s infinite alternate;
}
@keyframes width {
  from { width: 0 }
  to { width: 400px }
}