He overall really cares and tries to make it easy especially grading, nothing posted online through so I recommend always attending lectures plus weekly quizzes that were pretty easy. He graded easily too which I appreciated. Not great at lecturing but makes it clear what you should know. Overall, would take again.

overall really cares about his students! was an okay lecturer and nothing is posted online so you have to rely on your notes. the first two midterms were very fair and no curveballs. stressful sections were sent straight from hell, there is always a quiz. homework only worth 5% of your grade, so very test heavy class. slight curve at the end.

I retook the course with this professor after getting a D+ in my first attempt of math3B with a different professor and I wish I had him for math3b the first time. exams were fair in terms of difficulty and the professor was great at explaining most concepts and would show us multiple examples which i found helpful.

Casteels is the best college math profesor I have had so far. He is new, but he is an excellent teacher. Great clarity in explaining concepts, and he is very approachable if you ever have doubts. Go to lecture, do your homework, study 1-2 hours for exams, and the class is an easy A. I had him for both Math 3A and 3B, aced both classes.

Amazing professor. I'm taking his Number System and Combinatorics this quarter. The workload is ~4 questions/week/course. One of the most memorable moments was when a HW problem in Combo was a trivial case of an open problem. I emailed him at midnight, said I proved a stronger result. He replied super fast with tons of books and related materials.

Five points might be the upper limit of rate my professor, but definitely not the upper limit of Karel.