My father is an electrical engineer. Growing up, he had countless components in the basement, including a whole slew of 7400-series DIP chips, as well as a bunch of (powered) breadboards and spare wire. In highschool I had so so much fun building things from scratch - I recall building a basic adder by drawing out the truth tables and doing boolean algebra to come up with the circuit diagram, eventually evolving it into a more fully-fledged calculator. It felt (and still feels) like magic! Most of it was self-directed, though I certainly got his help in a lot of places.

I think sort of "choose your own adventure" projects like that are great, and they also force you to really understand everything you're doing. You can also scale the scope of the "project" to whatever you want; it can even be a sort of iterative process. More importantly (imo) you're left with a bunch of components that he can tinker around with endlessly :)

I so miss the basements of my midwest youth and early adulthood. They were the place for projects. I built so much. My west coast home since 2010 doesn't have a basement, and we've not much interior space for projects (esp when you're talking construction, tools, soldering and such). My spouse is stickler about the inside staying nice, too. The garage is the alternative, but it's so inferior. There's a car there, it's cold, etc. Oh for a basement...