I have some suggestions to make the app better
1. Lock UI
I think the UI(windows, brush orders, hot buttons...ESPECIALLY Hot buttons.. etc.) need a lock toggle. I keep accidentally moving them, and It's kind of a pain to resize them and put them back in place.
2. Filters
Filters such as Gaussian blur, Sharpen, Noise etc. should be added. It would make the experience way better!
These are the suggestion that I think me and other people need the most.
Thanks for making this awesome app for iPad!