Aaaaah I need a second person!! it's a bit tedious on your own, but I can see it would be a lot of fun with a partner!
Somehow Chrome wouldn't send my keyboard input to the app but insisted that there are four joysticks present (maybe some anti-fingerprinting they do?). When I connected the one Gamepad I have, I could control Blue with it, but no luck with Yellow.
Keyboard input worked fine on Firefox, so I still got to play!