The rotary currently only tracks mouse geometric position. For ease of use and for compatibility/similarity to other soft synths a basic up/down movement would be useful. Building in that motion will not be too hard. It has not been specified if it is to be screen height movement or something less. The request is from Simon, will ask him for his preference, or at least input on what the other apps do. In my opinion they don't do fully rotary tracking as it is quite a lot of work if it is not already a part of their graphics toolkit.