Hey I think I'm just dumb, but I couldn't figure out what to do after fixing the mirror with the red letters on it. Tried going through the mirror and said I need 4 symbols but the only symbol I could find was the heart key. However, this is a really cool game and I love the mystery and music. Really creative!
One recommendation I'd have is to make it possible to switch between the observe(eye icon) and grab (hand icon) with the right mouse button or spacebar or something just to make it a little easier to switch between the two.