It's cute! One thing to think about--and I have no idea whether this is something easy or hard to implement--is that it might be nice to be able to click and drag across multiple squares. For instance, in the first puzzle with its 8x8 grid and several "8"s in the clues, being able to click once and drag down the entire column would be easier than having to click eight separate times. But that's just if you're thinking about enhancements.