Oxygen is a pure CSS stylesheet with no classes
Visit https://oxygen-css.com for a live preview of oxygen on a website.
After downloading oxygen, use this code snippet to use it:
<!DOCTYPE html>
<html>
<head>
<link rel='stylesheet' href='oxygen.min.css'/>
<!-- allows responsive design -->
<meta name='viewport' content='width=device-width, initial-scale=1.0'/>
</head>
</html>