I couldn't agree more about the undo, tis a true lifesaver. However, there can't be different medias, just colors. Example, I paint a few strokes in "oil" then right into that I slap on some watercolor, they mix just fine. in real media that could never happen. Or paint on some water color then switch to chalk or wax crayon. and they all mix just like a big happy family. Although not realistic it can be fun and useful. And I'm not bashing AR because every other drawing package I've seen works the same way. I wish a little window would pop up saying "idiot, you can't do that."