I went on a little side quest before proofreading the book to make a larger JRPG prototype that's free and open source. That way readers of the book (and others) can see what a larger JRPG project could look like.
More details in this topic:
Or just download the game:
And get the source:
I took the last two chapters of the book and expanded them to have more systems and complexity. It was a lot of fun to just make something without having to write in depth about it. It felt freeing. I'll likely record a video walking through the source and explaining it for those who want to make use of it.