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!

The professor made the lectures very clear and uploaded them so I would re-watch them if I needed to. The majority of the grade lies on the two midterms and the final, and even then it is a total of 14 questions for all three of those tests. This class is kind of easy just depending on how easily math comes to you and how much work you put in.

Very solid class. Tests were exactly like practice ones, though final seemed a bit hard. Web work isnt the greatest thing ever and it was time consuming but it wasnt stressful. Uploaded lectures in full and his notes. Very manageable work load

He does have an accent that takes a while to get used to, but that's honestly the only negative thing I can say. Super clear lecturer, amazing handwriting, and really kind. He respects all his students and will help you understand something at OH if needed. The tests were also extremely easy, very similar to the practice tests. Hard to not pass.

Great lectures, super clear, takes really neat notes that are easily understandable. Made the class material really understandable and overall enjoyable.

Very good professor! Amazing handwriting too and explains concepts well.

He really set my expectations high for a math professor. His handwriting is unmatched and I realized the other math professors don't have as neat handwriting. He is AMAZING and seems like he really cares about his students. He explains things super well, although the class might feel kinda slow at times. It is easy but we don't cover everything.