I'm happy to have completed it. ^^ If there was a part I didn't understand well, I looked back at previous lectures, and if I still didn't understand, I sought out and read the official documentation to resolve my questions. This was possible because the lecture was created based on the official documentation, which is also why I chose this lecture. As the lecture proceeds theory-centered without mini-projects, it's a bit boring, but it was helpful as I could solidify the basic concepts. Especially, as in the "Ref Objects and DOM Interfaces" lesson, I liked the part where you showed how the code works through the inheritance structure between interfaces while looking at the spec document. Since I'm also studying Java, it was interesting to learn by comparing whenever similar structures appeared. Now I will continue with the roadmap to completely finish DOM. Thank you.