I'm constantly getting "NameError: constant FileUtils not defined for Object" when submitting or running tests in Ruby. I can't submit any Ruby solutions because of that.

I'd like to suggest using some sort of spaced repetition algorithm (like what Anki or SuperMemo use) to make practicing old katas efficient. Spaced repetition is supposed to pick the right time for performing a given task, based on your feedback and previous repetitions. The core concept behind those algorithms is surprisingly simple.

It would be great to have some sort of arena, where one could compete with others on time restrained katas. I find a little bit of direct competition to be a great boost to productivity. It would be so much harder to just walk off from a problem if there were other people struggling with it at the same time.

Anyway, thanks for the platform, I'm having a blast.