Wow, such a cool mechanic and really well implemented! The 3D modelling is great and the mechanic works really well - great interpretation of the theme and a really unique way of using shadows!
If I could wish for one minor change it would be a way to skip the stopwatch back to the beginning instantly - of course I could try to figure out the puzzles partially in reverse, but that's too much for my brain to bother with unfortunately! So a way to just play from the beginning would be great instead of waiting for the rewind. But I love how it shows how much longer is left on the timer (took me a moment to notice that so perhaps it could be bigger or coloured a little differently?) and that you can speed up and slow it down - many people wouldn't have taken the time to implement that as part of the mechanic, but it really helps with the player experience!
I also think a splash of colour here and there (more than what's already there) would be useful - I kept losing the potion bottles so if they had some colour it might've been easier to keep track, though maybe that would've made the puzzle more confusing... not sure!