there's no long-running JS so nothing invisible really accounts for it either. is the background's SVG noise having difficulty rendering on your machine?
It's not, like, the correct way, because I don't know what that would be, but if your browser has developer tools (or if you happened to already have something like Stylus installed) that let you apply e.g.
html { background-image: unset; }
you could see if that made the CPU calm down any, maybe?
The other two things that maybe could explain it would be the animated star GIF background (the GIF itself shouldn't be too bad, but maybe because it resizes with the page?) which could be tested a similar way with
#sideframe { background-image: unset;}
or the use of border-image, which really shouldn't be difficult to render, but which I've noticed e.g. Safari often gets weird about, so
* {border-image: none !important;}
The whole thing is developed on Firefox, so a bummer to hear it's having issues. (And someone above said it couldn't copy-paste – there's certainly nothing meant to do that!)
