It was a really big help to me but you forgot 1 major thing, well actually 2.
First one, there wasn't described how to make a button which sends you to the next level. 2nd, people can still cheat by pressing right mousebutton - Play. I also noticed that people could get outside of your level and in fact lose 2 lives, 1 for getting out and 1 for getting back in. If you're ever considering making a second tutorial maybe you could add more advanced options like how to put music in the game.
This tutorial has helped me a lot, but it could use some tweaking and more options.