I have the first cat working. For some reason my program suddenly stopped working, and nothing helped until I switched to a different Arduino core... I swear it worked before, so no idea what is going on there. Anyways, after some trial-and-error, desoldering, resoldering, reprogramming, etc. I finally got it to work how I wanted. Behold:

A little underwhelming, I know, but still fun. In the coming days I will prepare proper build instructions and will send the boards to people, who have requested one.