The game is mechanically almost perfect, it's just too easy. There's no challenge here, almost to the point of it not being any fun at all. An important part of a puzzle game is the challenge and reward of solving the puzzle. You have a great base to build from here, I hope you do something great with it!
Edit: you might want to check your win state calculation. Puzzle 31 can be solved multiple ways but only registers as a win if you solve it one way. Same thing with puzzle 50 and 59.