I was also thinking that each piece could have a magnet at the base. And when a piece is captured, the underlying gantry could flip the polarity with an electro

I was also thinking that each piece could have a magnet at the base. And when a piece is captured, the underlying gantry could flip the polarity with an electromagnet and sorta launch the captured piece off the board. Although it seemed like the author had other issues with using an electromagnet here (i.e. overheating / switching polarity).