Hey GaYoon!
First of all, I want to apologize for my late response. I didn't check my email for a week due to my hectic schedule and saw that I missed three questions from you. I am SO sorry. That will not happen again.
Second, I want to apologize for your having a hard time viewing the lectures. I'll make a note of it next time and think about what I can do to make the student-viewing/learning experience better.
See you in the next question,
Jin Teacher