This is caused by https://github.com/hakimel/reveal.js/blob/master/css/print/paper.scss

Even if I embed reveal.js in a page, it will override ALL THE BASIC ELEMENTS with !important, e.g.:

This means that output will have

@media print {
  html:not(.print-pdf) body {
      font-size: 20pt!important;
  }

  html:not(.print-pdf) h1 { 
    font-size: 28pt !important;
   }
}

So a normal page without reveal js like this:

Becomes like this just because reveal style is imported:

(I embed a reveal.js in page:)

My confusion is why is that file needed as users are already asked to print with ?print-pdf?

Also does anyone have the same confusion with me why reveal.js tries and why it should use high priority selectors and !important to force overriding default tag style?