I took both of his MATH 4A and 108B and he's always been very nice. Lectures are super clear and easy to follow. Lecture notes are provided. Really enjoyed talking to him in office hours as he is always so helpful and fun to chat with. Exams could be hard but if you study hard for the homework and practice exams they should be fine.

Great lecturer: clear handwriting, explains concepts well, and easy to follow (good pacing). Slight accent but generally understandable. Posts in-class notes online. One Webwork assignment per week. Provides helpful practice exams that are very similar to the actual exams. (Fall 2021)

overall not bad, he has an accent but you can still understand what he says. His lectures are very clear and midterms and finals are not bad as long as you study and go over problems done in class.

Professor Castella is a super chill professor. It's true that he has some accent, but he provides notes for all the lectures. The exams are pretty easy. If you work decently hard in the class, it's an easy A.

Took the class in Fall 2021. Lectures were made available online quickly, homework was very doable. Straightforward class and good lecturer.

Though he has a Spanish accent, everything he taught was so specific and understandable that there is no need for extra work in addition to listening to his lectures carefully!