In my case, all of my friends have the same username on both github and codewars. Might as well try your friends' github usernames before asking them

The number of shift is determined by the position of the key in the input alphabet. I first thought it's determined by its distance to ascii 'a'. Then I thought it's determined by the unicode distance to the first character in the alphabet. I think it should be put in the description.

Also there's no spec in the description describing what we should do if the key is not in ascii.

The behaviour should be specified when the data pointer is pointing to an uninitialized data point.
Looks like the current behaviour is setting the uninitialized data point as zero.