Solid puzzles! At first I got a bit frustrated, because I got stuck when I "spent" all the energy of the machine, and couldn't find a way to restart it, but after coming to the comments I saw that I just needed to press 'R'.
After that, things went smoothly. I love how you didn't made the tutorial mandatory, and left to whoever needed it, to read the book. I say this because I felt that the mechanics were really intuitive.
Love the concept of using the shadows to duplicate items, the overall theme of the game and execution! Amazing!