Slow Dance

I put two seashells in it from our trip to Maine, and for the first day I honestly couldn't figure out how they seemed to be drifting when nothing was moving. The illusion is subtle enough that you catch it out of the corner of your eye, which makes it weirdly hypnotic on the shelf.

The slow-motion effect is genuinely cool when you catch it at the right angle, but it only really works from straight on. Move a foot to the side and the illusion mostly disappears.