I've been working through the COSMOS tutorial, (which is a fantastic idea, by the way), but I've noticed some problems, especially with the navigation ('previous'/'next' chapter buttons at the bottom). In particular:
Chapter 5's next button points to ch 17
ch 6's previous points to ch 24
ch 8's next points to ch 10
ch 9's previous points to ch 10, and its next button points to ch 11
ch 11's previous points to ch 9
ch 16 has no previous or next buttons at all
ch 17's previous points to ch 5
ch 24's next points to ch 6
Also, chapter 10 is empty (i.e., has no content) and there is font size issue with chapter 12.
Also the AstrologicalSignProvider.swift file which is linked in chapter 7 uses the prefixed classes C4Point, C4Path, and C4Shape rather than classes Point, Path, and Shape used in the framework.
Anyhow, I think the idea itself is great, and I'm excited to get started.