This is the first time I've had a lecture with this kind of tension, and it was really breathtaking without being boring. This is the first time I've had a lecture where I didn't increase the speed while listening to the lecture, and since I had to pause a lot in the middle to understand and fix bugs, it actually felt like a 3-hour lecture instead of an hour and a half. It was so good that I couldn't believe it was free. Thank you for the great lecture.