This really only becomes a problem in the Master set, but there are just some puzzles that are impossible to solve because of those stupid numbers that keep getting in your way.
On that matter, I'm giving this a 3/5. While I absolutely love this game and think it's a great concept, there are just too many glitches. I'm sure you can fix them, and then I'll probably give this a 5/5.
I feel like this game was simply to difficult. A hint at the beginning of each level, I feel, would make the solution easier to find, but would still grant some satisfaction to the player when they finally figure it out. Take Something Literally is a perfect example of this method.