Something that would be nice at the end: A skip or speed button. It takes forever to get through it, and it goes again if you replay the final level. :( Too slow at the end. Nice game, though.
The game gets horribly glitchy from time to time and has become irritating to play. =/ I don't know what happened. I got like 10 lines with no gaps in them, and none of them cleared. =/ Took my rating from 5/5 to 2/5.
I rated it 4/5 because of one thing: controls. It would be a bit easier if you didn't use wasd format. That's harder to remember than arrows. I have to double check my fingers before a level. >_<
Nice game for no frills. So, all these people come here and rate it 1/5 because they hate sudoku? That makes no sense. Why come to a sudoku game then? xD 5/5