Cool! Might be neat to make it more clear which layer you're editing. Was a bit confused when I first started using it. It does seem like a very powerful way of creating this type of art!
Now that Procjam is over, I'm in the middle of rewriting the application. Because of the experimental nature of what I was doing for procjam, it was very difficult to add stuff like this after the fact, but now that I have a better picture of what the application needs to do, I'll be able to add a lot of quality of life improvements.
Thanks for the suggestion!