I noticed the same thing, so I just did lessons from http://regexone.com/problem/trimming_whitespace.

As soon as I finish their problems set, I look forward to redoing many of my lower level katas.

If I still need regex help, I've got http://qntm.org/files/re/re.html and http://regex.learncodethehardway.org/book/ queued up.

Thanks for tHe feedback! I do plan on going some tweats at some point. The kata was written before ES6 support (Babel) was introduced, and as I can't turn it off it broke quite a few things that were perfectly valid before (like anonymous functions, they now get auto named).

After re-reading the description, it seems like it could be made more clear. However, I'm not sure if your suggested changes to the description accomplish that. I'll be sleeping on it, particularly in regard to this sentence and the following example recommended previously "The shift is derived by applying a Caesar shift to a character with the corresponding index of the key in the alphabet."

Edit: In regard to difficulty, it was determined by the beta process, and it seems to fall in line with other cipher katas. It should also be noted that, although this was published before Python was supported on Codewars, that this kata is much harder in Python because Unicode support sucks in Python 2.x.

It seems to be the current mainstream belief that the power of abstraction required by regular expressions and functional programming displays superior problem solving ability than old-timer loop solutions manually covering edge cases. I happen to strongly share in that belief as an old-timer stateful programmer myself. I believe in doing everything we can to push ourselves to the next level of excellence.

You can easily disable regex in your kata's which does force other people to use another method of solving the problem.