I'm stuck exactly at this test case... any pointer would be appreciated. To be honest, I don't really understand how the alogrithm works when x is a float. To me it would make sense to round x**n but this is not what the author wants. Pretty lost here.

Hello, when trying to pass the Katakana tests, I have an error on the fourth or fith test.
However, the output of my code is ドモアリガトゴザイマス (which looks valid) and the expected string is ドモアリガトゴザイマ��� which seems invalid to me. Am I missing something?

Great kata, it took me a while to figure the best algorithm to do it. Thanks for this brain teaser :)
Couple of suggestions though: I think the sample tests are too easy to pass, so they don't give you enough feedback on the quality of your code. The sample tests should also take a longer time to compute using an optimize brute force algorithm, this way you can give a metric to people on how likely their function will pass the final test. Let me know if this makes any sense.

Great work, seriously!

I would definitively specify that the sum of the output should be the value.

I really like it otherwise, short but pleasant.