@LukeAlmighty That is interesting indeed, especially since basic math is something 99% of kids can grasp so you don't see people fail with it, but with programming there are hurdles that some just can't overcome, and seeing them try is... intriguing.

First when they finally realize how loops work, and stop putting return statements in the loop body.

The second hurdle is recursion.
That hits people hard, and is the biggest test for devs in general.

I've never met a good dev who didn't understand recursion.
It's simple, but abstract and completely new.
A self referencing rule, that is the reason many quit software engineering.

CSS rules, REGEX, parsing tokens, and SQL statements, are last but not least.
Selecting items by describing the group, instead of describing the method, as well as mutual recursion, are entirely different approaches to get things done, and it's difficult for many to fit into their heads.

If you get past all that, you definitely think differently.
One line a time.