Aschenbrenner is an awesome professor. Not only is he a clear lecturer but also an understanding and great person. He effectively taught this class virtually and ensured we understood the material (even asynchronously) by being available on email. 131A is definitely not an easy class but I think I was able to take the most out it because of him. Would definitely recommend him for any class.

Note: he did tweak the syllabus and decided not to teach limsup and liminf, which I think is important for any Analysis class.

Matthias is a very clear lecturer, and effectively builds up the course material from the ground up, which is the purpose of this class: proving the material of single variable calculus from first principles. He gave easy tests, with medians of 79%, 68%, and 81% (Midterms 1 & 2, then the Final). I got 98%, 93% and 96% by just ensuring that I knew and understood the import definitions/theorems from the class. The homework problems can be challenging, but extra credit problems on them should keep your HW grade close to 100%. He does grade on the absolute scale. Very chill guy, would take a class with him again!