JSFiddle - React, Tailwind, and code Playground

HTML

Resize result pane to 16px * 40 = 640px to toggle the background color. The base font size does not seem to matter.

CSS

*,
html,
body {
  font-size: 50px;
}

body {
  background: yellow;
}

@media only screen and (max-width: 10em) {
  body {
    background: blue;
  }
}