The navigation seems like a big improvement over the old version.
You might want to show if one side is solved correctly, or show what numbers are missing, but it might against your philosophy, since there seems to be no indication if the number you've put down is right.
Can't erase the placed numbers.
Unclear what tile you have selecte at the moment if you're selectin on of the "wrong" numbers you've put down.
No exit button.
Congrats on the looming release!