All four launch machines have a game you can finish

The four machines the course launches on — the ZX Spectrum, Commodore 64, Commodore Amiga and NES — each now open with a complete, finishable game, built one technique at a time in the language people used at the time.

That’s the whole promise in miniature: not a toy exercise, but a small real game with a title screen, a win and a loss, that you build up from a blank screen and can play to the end. Pick the machine that pulls at you and start there.