I used TypeScript in my field and wanted to understand TypeScript better, so I paid for the course. I was only going to watch the practical analysis part, but I paid for it with the thought of brushing up on basic knowledge, but there were more parts I didn't know than I thought, so I think it was a good idea to start with the basic grammar part. In particular, I understood it even better when I analyzed the type and looked at the operating principles. Thank you for the great lecture.