My nephew has an obsession with latches and buttons (another budding engineer in the family?) so I made him this playset.
The centerpiece is a borg alcove lightning thing which is voice and sound activated so if he presses a button, bangs on the plexiglass or giggles it flashes. It also displays a little when the motor of the disco ball is on. There's also a plasma globe on the right, more flashing LED baubles at the front, and a blue button with a countdown beeper. At the cardinal points of the lightning thing are fiber optics with flashing lights that's governed by the trackball so when he moves it one way one set flashes, and so on. The strip at the front is assorted bits of holographic paper/plastic I had left over from other projects, as well as a strip of liquid crystal which changes colour with temperature (so can show you the outline of your hand or finger if you put it on it for a second). Everything's under thick enough plexiglass I can walk on it.