Great, simple concept that offers infinite possibilities. Trial-error cycle works nicely without any delays. I didn't even miss the reset-button as I usually do.
Few mandatory issues:
- Sometimes when you move the outer circle, you accidentally scale the bigger one. For such mishaps, undo-functionality would be nice.
- Solution disappears immediately when level is finished. As puzzles can have multiple solutions, I'd like to be able to save or record them after finishing the level.
I'm looking forward to new levels. This could be a nice basis for procedurally generated puzzles also.