I played this myself. It goes on forever, but I only played it through about 3 times. Click the little cats to hear different versions. The dark pink one is the reversed theme. The blue one is a higher version. Press the arrow and wasd keys to move the smaller cats around.
Nyan cat theme piano from musescore.com. Here is the link: https://musescore.com/user/16971476/scores/3952411
