Thank you for the suggestion.

Looks good even if counting the errors using [a-m] would have avoided to do the substraction.

Nice to see that my solution was exactly like yours :)

I would love to see a feature that shows the number of honors I get (and how much closer to a rank I will be) if I solve a kata BEFORE solving it. This would make it easy to understand how your ranking algorithm works as based on comments below it is a bit unclear at the moment. In addition to that, even better it would be if you automatically suggest a kata to solve that maximize the ranking up. In any case, more details on the algorithms are welcome.

Could you please explain how you come up with this formula? Thanks

Oh yes, you are right. I found the problem in my solution and now it works consistently. I mark the kata as ready. However, I still think that it would be better if you take the random tests and codify them so that alwyas the same tests runs otherwise it is possible to run the kata many times until your crappy solution works and submit an incorrect solution. Thanks. I enjoyed the kata. (I resubmitted a fixed solution but it does not seems to override the one I alreadu submitted)