Thank you for the kinds words! I'm glad it was helpful to you. :)
The main reason I'm not using local variables is that while the tutorial is certainly useful for people who have some experience programming, it is designed to be able to be done and understood by someone who has almost no experience coding. As such, I tried to limit the use of local variables to just those variables passed into functions, as I didn't want to try to get into the concept of local vs global variables at this point. In my experience, it can be a tough concept for some people to get their head around, and they're already trying to absorb so many new concepts already. (This is also why each step of the tutorial just adds to code you've written, rather than going back and changing lines of code that are already written.) Hope that helps make it clear. :)
Unfortunately, the disabling of comments is from YouTube, not myself. It is unbelievably hard to reach a real human being to get it resolved, so until then, I can't enable comments. :(