Been watching this series recently. I doubt I'll actually make the thing, but I've been finding this guys teaching style really fascinating. It's definitely making me want to get some breadboard and start tinkering with electronics:

https://www.youtube.com/playlist?list=PLowKtXNTBypGqImE405J2565dvjafglHU

Looks interesting.

My youngest son is at the beginning stage of an electrical engineering program.  They recently built a simple add / subtract using and / nor individual transistor elements.

For fun we did an estimate of what it would take to use the same approach and multiply 1000 x 1000.  Pretty amazing how quickly it can become impractical.