When I was making a chat program, I was impressed by how you drew the structure in an easy-to-understand way. I never understood what object orientation was no matter how many times I heard the explanation, but now I think I'm starting to get the hang of it. There are many places that teach theory and grammar. However, I think Younghan's lecture is the only one that shows how the concept is actually used and makes you feel why it's necessary. I'll have to listen to this lecture a few more times while drawing it myself, as you said at the end. I always get strength from you helping me become a better developer and cheering me on. I'll wait for the next lecture. Thank you.