I'm having the same issue. Running the string through my encryption (which resulted in correct answers up until that point), gives me a different string than the answer they expect from decryption!

I would like to know how can this assert be true:
Assert::That(encrypt("This kata is very interesting!", 1), Equals("hskt svr neetn!Ti aai eyitrsig"));

Until the 15th run is fine, but then you are the the "!" position of the "This kata is very interesting!" and then you go to the "T" word wich is the 1st after the "!" word?
Shouldn't be the "h" word, wich is the 2nd after "!" ????
Can someone explain me why this is the right encprytion?