This guy is very intelligent but clarity is not great. If you fall behind you will be lost.
He is a great teacher who builds from simple to complex concepts in math. If you slack off and fall behind you will not catch up.
If you're a math whiz, then this is YOUR teacher. For the rest of us, it's extremely difficult - and once you fall behind, you CAN'T catch up. Period.
Mr. Nong already has in his mind his star students and it is seen in his grading. His grading methods are inconsistant. He is more intimidating than helpful.