Mission is a Failure
There are also a lot of other weird things going on in the sample code. Lot of magic numbers that correspond to either room numbers or codes for certain types of tiles to display. And there are lists of tuples where you need to know what field is in each position of the tuple. I have just about given up trying to follow the code that is presented.
I also thought I would be learning some Pygame Zero modules details. Nope. Not yet at least. I am trying to gain some wisdom on the algorithms and techniques used for the game development here. There are a few items of worth such as animating movement or controlling shadows. Can't wait to finish this book so I can begin rolling my own adventure. And I presume I will just use straight Pygame to do the graphics.