Really neat puzzle game. I actually kinda like that you have to rush for the first half and then you get to stop and think.
There were a couple issues I had. First is that the shrinking animation takes too long. You just sit there and watch it for a while, and it feels a little overdone.
Second, you can very easily just drop the box off the edge and have to restart the puzzle. It would be a lot nicer if the box respawned at its original location on death. You could even use that in some puzzles if you establish it as a mechanic.
And finally, I noticed you said there are 12 levels, but I was only able to do up to 8. After I beat 8, none of the other levels opened.