Yeah, for me, analog is the exciting domain — my undiscovered country. I have played with vacuum tubes as well and thoroughly enjoyed it.

Transistors were, for some reason, seemingly unknowable to me. But I made a kind of "transistor playground" [1] based around Forrest Mims III book [2] and then enjoyed playing with them.

[1] https://imgur.com/a/dChq4AZ

[2] https://archive.org/details/forrest-mims-basic-semiconductor...

Edit: actually, I had forgotten it was a transistor logic playground for I made for creating logic gates with transistors. Based on another Forrest Mims book: https://archive.org/details/engineersmininot00mims

That looks awesome, nice work! Very clean.