All right, I’ve had a chance to review this chapter, and I made some changes.
In the Add the Player Agent to the Component System section, I end with this:
Build and run the project, but don’t pick up the key right away. Give the monsters some time to wander around first. After a short while, pick up the key, and watch how some of the monsters’ attention turn to Val. (Don’t worry, the monsters still can’t hurt Val, but you’re about to work on that next.)
That paragraph above indicates that the monsters will chase Val after she collects the key. Of course, the monsters won’t chase her because their entities haven’t (yet) been added to the scene’s entity array.
To fix this error, I’ve modified the end of that section, which now reads:
Excellent, the
didMove(to:) methodis cleaner, but there’s still one more thing you need to do: get the monster entities to participate in the updates.
I also added a new section immediately after the Add the Player Agent to the Component System section, which looks like this:
And, I updated the Update Physics for Monsters and Projectiles section to reflect this change.
This flows a lot better and doesn’t give the reader the impression that they may have missed a step. Thanks for finding this one!
I don’t think another beta is coming out, but the “fix” will be in the final release. Marking this one solved. 
