Every time I attempt to do something more complex than a simple edit on my iPad Pro 9.7 I get a black screen with the word "wasted" in it. At times, this will continue on an endless loop until the app is quit and relaunched. Closing additional apps in the background seems to help sometimes, but it occurs even with Polarr is the only thing running. Makes the otherwise very good app unusable.
On another note, please please please give us the ability to draw masks, in addition to using the various circular and gradient tools you already have. Sometimes its just easier, especially with the Apple Pencil, to just draw a small area than try and create some kind of complex circle mask to fit an otherwise rectangle area.
camhabib about Polarr: Photo Filters & Editor