This rainbow LED busy box was built entirely with parts on hand. It’s controlled by an Arduino Mega and powered by a USB battery pack I got free with some promo. It distracted my two and four-year-old nephews for at least ten minutes, which is pretty good by their standards.
Inside are addressable LED pixel strips, toggle switches, and 3D printed baffles. I recessed the switches into the case for clearance. The result is something less conventional looking than if I recessed the light panel, but gives the diffusing plastic more depth for a much better effect. I made the grid an even eight lights wide with the idea of upgrading it into a step sequencer in the future.