Part of the smoothness here is that scrolling the text is 1:1 once you get down to the sections with colored headers. It demonstrates that it's possible to make a page look fancy like that without "breaking" your intuition of what scrolling "should be."

JS animations obviously don't take the place of video/audio media that you'd play/scrub through.

Hey I'm the author of the lib, exactly, I don't really "highjack" the body scroll, I'm only controlling the background animations with it, while keeping most of the body content scroll naturally with the page.