After I finished all the levels from Worlds 1 to 14, I was wondering why the last achievement did not unlock. I checked my progress and it said that I finished 126/127 levels. I couldn't find any other level so I did a bit of searching and found out that there's a hidden level. There's no guide here so I decided to make one for it.

Anyway, to find the hidden level, just go to the bottom of the credits.



The hidden level can be accessed only after finishing the other levels. To check, I cleared my game progress and went to the bottom of the credits. If you haven't finished the other levels yet, you'll only see a blank box in the space where the hidden level should be.