I like the game, but I'm not a fan of the scoring system. Accidentally clicking wrong is bad enough, but for me, accidentally clicking a right square is even worse. I want to be able to solve the puzzle logically, not by guessing or accidentally getting a square right. I'd want to be able to uncheck a square, and I don't want the game to tell me if I got it right or wrong.
I also feel there are things missing. I'm on Normal mode now, so I don't know if this is in later levels, but I really miss more colours.
Difficulty of puzzles varies wildly, for example, Steamed Rice is dead easy, but Kite is impossible. Literally; I'm stuck, I can not finish it without guessing. Several 15x15 'Normal' puzzles could've easily been used in Easy mode.
All in all, good game, good programming, but I don't like the execution and there are some issues that could be improved.