I've been using LaTeX for a few years for typesetting maths documents but I kind of feel there are two "kinds" of latex: the one I write my documents in and the one packages are written.
My goal is not to write a package, but trying to solve problems by my own. I often find myself searching for solutions to every problem I face and the answers always involve this syntax I'm talking about, full of
@s, and things like
\catcode. Since I can't understant it, I simply copy it blindly.
What's the recommended resources for learning this not-so-basic latex stuff?