To play the game you press the button. The button state is fed in to an XOR based edge detector that triggers a 555 timer. The timer sends a timed pulse to the inductive driver (L293D). The driver drives the electromagnet to make the pendulum move. A down press of the button energises the coil in one direction and releasing the button energises it in the other direction. There's also a separate 555 timer in astable mode. It's generating an adjustable square wave that can be used instead of the button to drive the pendulum. This is kind of like a second game where you have to play with the frequency and duty cycle of the square wave to get the pendulum to swing freely.
I've had this idea for a pendulum game for a while. I like how there's very little you need to know to play it. There's only one button, and pressing or releasing it energises the electromagnet either one way or the other. I built it out of parts I had on hand. That is the reason for some of the odd passives value choices. The bearing for the pendulum is from an old hard drive. The electromagnet is an old bolt with wire reclaimed from a VCR head. I had some extra Gateron brown switches and printed a one switch holder. The base is made from a small scrap of plywood and some pine.
In the future I'd like to have a larger pendulum in my shop hanging from the wall. This is a good test bed to get things started and try different circuits. I'm also thinking of adding a line of LEDs to create a POV display. It could display the highest angle achieved.
The KiCAD files and pdf schematic are included in this project entry.