Good drawings!
Quite a handy tut indeed!
But remember that it's us newbies that are most likely to view this tutorial, so you should've maybe tried to make something more practical and understandable by making it an easy image to work with.
But otherwise, very good drawings. Interface is superb and I love the next/previous... you can run through them quickly without having to wait.
Nice job!!! Now make one involving animation and shading. Please! ;)