Just iwanted to say, what a great exercise! I just did Happy Birthday, the first two parts went easily enough, but that last part was intersting. I ended up being a little off on some of the notes, but not bad. The only thing I had "wrong" aside from those few notes was I was playing in G instead of C.
Even though it's a simple song, it was so satisfying to realize I could figure it out that quickly. I hope we get more exercises like this.