[jon-wood]

If you want to go really deep on this I highly recommend NAND To Tetris, a book which starts from the basics of combining NAND gates to build basic logic. You’ll gradually work through building a CPU from those components, building an assembler to program it, and finally putting a virtual machine on top of that.

[dbrueck]

Haha, I came here just to encourage people to check out www.nand2tetris.org too. It's extremely educational.

It's also realllllly satisfying to play Tetris on something you "built" all the way up from basic logic gates.

It's a great (and free) course during a pandemic lockdown or a fun project over a holiday break.