When I was in a freshman math course, a professor started the semester with a warning: "Trying to learn math without solving exercises is like trying to teach a toddler to walk from physiology textbooks". Yet, I haven't found a good source of exercises for introductory category theory - is it the case that exercises for this subject are hard to come by? Or maybe it's a relatively advanced subject, so there are few books, and as always most books don't include exercises for some strange reason? Anyway, would love to hear where I can find exercises on the subject, if anyone knows. (BTW, I don't mean sprinkling an exercises or 3-4 here and there like in the OP, I mean like 10-15 exercises per lecture, which was the standard when I was a freshman)