Play-doh buttons and other things.

FWIW,

Love Jay Silver! Thanks for sharing.

I just watched that video, looked at 20 other videos about it.
Then I found this.

And I came to these forums to ask if this can be done with just the Arduino?
I have, very little programming knowledge and even less experience with creating pee driven systems.
But it looks highly entertaining, and I have motivation to try this.

Yes, that's possible with an Arduino or standalone AVR chip. It's probably something that would go physically viral in college dorms and might be a source of pocket money for an enterprising student with soldering skills.