ncrtorial is a tutorial I made from 2018-2019 that
deals entirely with game elements that are not documented in the pre-existing built-in tutorials, such as DC2 magic walls, Magic Balls, and white keys. It uses a sidebar design by Eizzoux that displays white keys and the four extra Emerald Mine Club keys.
I kept holding it off because I wanted to add more levels to it, but never felt motivated to actually work on any. Well, 3 years is enough waiting to see if new levels spontaneously manifest out of thin air, I think.

I may update this set later to include additional topics like starting inventory, but no promises.
Download
Contains 8 levels (00-07).
Permission is granted to bundle this levelset with future versions of Rocks'n'Diamonds.