I don't have an Apple so I can't evaluate yours. I use Nonograms Katana. It was Reddit's consensus on the best one. Its UX is OK. The biggest issue is that it

I don't have an Apple so I can't evaluate yours. I use Nonograms Katana. It was Reddit's consensus on the best one. Its UX is OK. The biggest issue is that it can be tricky to exactly tap with a finger. It has a tool for using a cursor rather than your finger, but it's a bit clunkier. It has the advantage of user-contributed puzzles. There are a lot of them. The biggest thing I really want is a save-and-restore feature. That way if I'm forced to guess, I can more easily revert to where the guess was. Good luck on your app.