Ask HN: What are topics that you want to learn but haven't gotten around to?

Category Theory (and more advanced Set Theory). After taking an undergraduate Set Theory course I want to explore these areas of mathematics further. I'm currently going though Thomas Jech's "Set Theory" on the Set Theory side, but haven't yet found a good, undergraduate accessible, Category Theory text.

For anyone looking for something to learn, I'd heavily recommend Haskell. It's been an eye opener for me.

In no particular order:

- A deep and real understanding of the blockchain.

- Clojure. I've heard that it is not only fun, but changes the way you approach programming in general. I don't have any professional need for it, though.

- Truly understanding how neural networks work.

- Rust, although this is similar to Clojure above; I don't know what I'd actually use it for.

I'd really like to get into hobby electronics, specifically DIY guitar pedal design.

There's a great subreddit, /r/diypedals, which I've been lurking for a while, I just haven't made the dive into buying my first kit and soldering equipment. Does anyone here on HN have any tips or words of wisdom?