The instructor is using the MacBook microphone as is, and the keyboard resonance and low-pitched keystroke noise when he types on the MacBook keyboard make it difficult to listen to the lecture. He types hard on the Enter key, and it annoys me so much that it's hard to listen. Instructor... There wouldn't be any problem if he just used a standing microphone that costs a few thousand won, but he's so insincere. I want a refund -_-;;;