and more in
++ All the info you gave was correct.
--- The 'explanation' was a little odd. I already know how masks work, but took me a while to realise you were trying to say just what you should.
I think your words could have been clearer. Also, I prefer a 'hole in a piece of paper' analogy.
--- I don't like the way that the whole thing was mainly a step-by-step walkthrough - it seemed like more explanations could have been used.
-- Some details (which I feel are important) were omitted. Can we see the mask effect when editing? Can we animate the mask itself? Can we have partial-opacity masks, like in photoshop?
I think it'd have been good to mention these.
- And some details seemed pointless. Your choice of frame length and layer names is your personal preference. To put them in the body of a tutorial might confuse some folk who come away unsure what's required and what's optional.
++ A decent effect.
==
An OK tutorial. I mean it teaches the basics. But it could be clearer and more in-depth.