Y’all talking about Calculus brought back memories. After taking Cal I, II, and III and making pretty easy A’s in all three, I hit Advanced Calculus with a professor who once worked at NASA and only gave a midterm and a final. Those were our only grades. Furthermore, both exams were exclusively proofs of the theorems that we had used along the way in the earlier calc courses. I think he did something like prove 6 of 8. I can’t remember. I managed to escape with a B.
But by far the most challenging math course I had was abstract algebra. I would never want to do that again.