This toy is a simple clear box full of water and colored oil. As the box is moved, a small circular weight slides up and down on a track, changing the flow patterns of the oil/water mixture. Somewhat of a passive toy, it just requires turning over and the weight will fall and cause things to flow.
Based on the mechanics of fluid flow and the chemistry of oil/water interactions.
The box itself would probably be some kind of clear acrylic or thin glass, the weight could be anything but metal would be the most interesting, and the oil and water are just that.
