As far as some proofs go, half are very easy to understand and apply to problems while the other half are ridiculously challenging. Quizzes were easy. Each assignment had at least two proof questions that nobody seemed to be able to get 100% correct. Mark’s a great lecturer as well as a good human being. However, be sure to attend lectures - the notes he posts won’t be enough to help you understand what’s going on. This course requires a $100+ textbook that is impossible to find online. It doesn’t contain any solutions and most of the assignment questions will come directly from it.