Hi,
For some reason I did not get see notifications the past month about recent activity on this kata.
Thanks for your observations, I've updated the description so the letter case and mapping exceptions are clear. You made a good point about the arbitrary mapping of 0 and 1. I will update it in the next version to be more useful to the puzzle, should probably also make sure the update does not invalidate existing solutions.

Thanks!

Merged! Cool solution btw :)

Added the random test! Please let me know if it can be improved further. Thanks!

Thanks! I see what you did in your solution! Will look into adding a random test case.