What should the interactive animation entail? (Patreon)

Here we go, the first Patron exclusive poll, you help me decide what KIND of interactive animation it should be.

I'm ordering these by difficulty, ranging from easiest, most likely to succeed, and quick to make, to harder animations that might take longer to complete, or something I have a good chance of being unable to make.

If I fail, I'll pick an easier winner from the poll.