nostr:npub1lnjf20p2kruz4spaf8ulr2xn8xgrkl3nzh97q8qv34n9v0xxgm3qxngg9l -All the material, including puzzle answers, is lurking on the Wayback Machine.   Lectures:

https://web.archive.org/web/20210418143549/https://forum.azimuthproject.org/categories/mit-2019%3A-lectures

Exercises:

https://web.archive.org/web/20210413111657/https://forum.azimuthproject.org/categories/applied-category-theory-exercises

These are the exercises from the book.   The puzzles and puzzle answers are around here somewhere too... but not extremely easy to find.

 nostr:npub1hc32he4lj9x92n7qx0y0xxcz66h8w9czskugl63nfjjqxatedwsqrg9dyu