Hey, that was an awesome mechanic. It did take a little bit and some hard puzzles before you actually introduced it, but once you did, there were some clever puzzles in there. I think a really neat design choice was to give the player the choice of which key they were going to lose when exiting the slime puddle -- it adds complexity to the puzzles in an intuitive way and gives room to more interesting puzzles. And later the rotation mechanic is really clever.