Difficulty is subjective.

Thank you. Excellent explanation. :)

Next to the "Share this kata" section. Note that only approved katas have an upvote link. Beta katas get upvoted if you classify them as "ready".

Where do I press to upvote katas?

You should be able to up vote any kata that you have completed. If this isn't the case then its a bug.

Don't see your solution . . .

This should have been fixed a few days ago. Is this still happening?

Thanks; I'll add one like that to the description.

There aren't any particularly tricky test cases. The closest to a tricky on is appending a list to itself. If you somehow make that into a loop of sorts, then you'll run into trouble calling length() on it. Other than that, it may just be load on the codewars servers? shrug