I don't understand the PPT reading style explanations like "A did B, then C~" (A, B, C are technical terms). The instructor's pronunciation and speech style are not good. There are a few cases where he explained things completely the opposite way, and he didn't even explain it properly and just passed over it. It feels like a lecture for grading seasonal semesters, and it doesn't seem to be a good lecture for a clear concept. I guess it can't be helped because it's a free lecture.