I <3 Codewars. This tool is what really helped the concept of functional program stick for me because the most elegant and simple solutions were invariably written in the declarative style. This made me envious and I studied them religiously. Slowly but surely my confidence in FP grew with each challenge. Recently I began reading SICP and programming all of the exercises in Scheme, a dialect of Lisp. It all just fell into place like the last corner of a solved Rubik's Cube. I owe it all to Codewars!