This is a fun game! At first when going into it, I thought I'd be able to endlessly duplicate, but once I realized how it worked with shadows it felt much more interesting! It connects well with the story in how duplicated things feel 'slightly wrong' to characters.
I enjoyed the puzzles! I think the highlights definitely were the one with the low energy salt machine and the last puzzle--the salt one being a good one to get you to think outside the box and the last one being a great overall one that makes you use a lot of what you learned. I think the pacing was good overall too, definitely felt like I was learning how the game worked at a solid pace.
Overall, great job! I don't think I have any constructive criticism on gameplay--I think it's good right now, and there's room to add more and continue it if you want. And of course there's always room to refine things as you update.
I'm glad I played this game! Thanks for making it :)