I really like the idea, and it worked well enough that I could play to the end with all the potions found.
However, the game could use a bit more visual cues as to what I'm actually doing. Unless I am completely mistaken, there's nothing hinting at what is the right shadow, so what could be a challenging puzzle game kind of turned into "run around every object until you stumble upon the correct one" for me. Which was still enjoyable, but it was less of a game than it could have been in that regard.