achieve crt scanlines on profile?

your current implementation looks alright - and if you're content with it, disregard this post, bweh - but if you want a slightly less subtle B&W horizontal-line approach, combine it with (or ditch the existing one and add this on its own):

html:before {
  content: " ";
  display: block; position: fixed;
  top: 0; left: 0; bottom: 0; right: 0;
  background: linear-gradient(rgba(0,0,0,0) 50%, rgba(0,0,0,0.16) 50%);
  z-index: 2;
  background-size: 100% 2px, 3px 100%;
  pointer-events: none;
}

exact same deal, just simpler to read 'n look at. neat profile, btw.

How to find out how you can look through the geometry dash and follow along.