[anyfoo]

That can easily be part of the fun (and learning aspect), though: The detective work in researching what the real system does, based on analysis of a real system (if you have one) or just derived from what available software titles do and expect.

Some documentation is good to get you started, but at a certain point it’s the actual software that should be the guiding factor. Inaccurate documentation, which is not uncommon for the Game Boy, can be unnecessarily misleading though (on the other hand, there’s some satisfaction in essentially proving a different behavior, especially if you accept a piece of documentation to be likely inaccurate from the get go).