[flying_kangaroo]

Not OP but also had to write my own shell, as well as the kernel APIs for forking and whatnot. The kernel APIs are definitely interesting, but I think the biggest dopamine rush was once the way to parse and structure commands "clicked" and suddenly shells made a whole lot of sense.

[yolesaber]

also being able to look at the source code for a kernel and saying "ah ha! so that's where the process table is created" is also a lot of fun...kind of like uncovering ancient artifacts and learning to read the glyphs