I think you could've kept the section on "basic recursion" short, keeping the focus on complex cases. I.e. removing any definition other than normal & tail rec

I think you could've kept the section on "basic recursion" short, keeping the focus on complex cases. I.e. removing any definition other than normal & tail recursion, and shortening the "tree structure of regression" bit into 1 paragraph. Most people do understand basic recursion and the function call tree, but fail to grasp it in nontrivial scenarios