What library is this site using for animations tied to scroll??

I cannot figure out what this site is using to tie animations to scroll. As you scroll down, you'll see the header and its text change size and position, and there are several SVGs that spin and move down/up the screen tied to your scroll. It doesn't seem like they're using any library that I recognize (e.g. GSAP, etc) but maybe I'm missing something? This is driving me crazy. Thank you!