Today’s invention is a toy which works with one’s iPad (remember when everyone thought that was a stupid name?)
The toy is a bristlebot variant which carries an optical switch pointed down at the screen.
As the bot buzzes about and lands on a dark region, it presses the screen causing regions to change their lightness/darkness. If the screen is locally light, the bot buzzes off somewhere else. Thus, the whole thing behaves according to nonlinear feedback (with some visual noise added).
Should be fun to set going in a browser window (with the screen adjusted to high contrast).