Wow, such a cool game. I had lots of fun playing this puzzle game. Very innovative twist on Sokoban. I really liked the tutorial and the level design. Difficulty of levels increases gradually and you learn on the way new tricks on how to solve the puzzles. The undo button is also great and helps a lot.
Some minor things you could improve are adding sound effects (especially when you squeeze and unsqueeze a sponge) and maybe a nice tween / animation for the sponge squeeze. And something very minor: Think about the buttons you use. I think ENTER / SPACE (for pulling) and BACKSPACE (for undo) would have felt a bit more intuitive. And keep in mind that some people in strange countries (like myself :)) have QWERTZ keyboards. So Z is not always the best choice, or add also Y as a possible button to it.
Congrats to this great game!