Looks like CannonJS [0] and CreateJS [1] are being used according to the Chrome dev tools "sources" section. If you look under "hplogo-complex" on the page it seems there a bunch of sprite sheets loaded.

Still not sure how it is all pieced together; I was under the impression that cannon was used in 3d. Would be great to hear more detail on this!

edit: a link to one of the JS files running it, seems to have references to all the in-game text, characters, animation states, ect. : https://www.google.com/logos/2020/kitsune/rc6/kitsune20.js

0]https://schteppe.github.io/cannon.js/ 1]https://createjs.com/