I'm really loving the game. Good work! I was thinking about something that can up the scare factor a bit... When you question the Doppels and they show themselves. Can you make it so that when you close the shutters they start banging on them? I want it to feel like the Doppels are even more hostile than they seem.
Other than that 10/10 game!
Edit: OH! And some additional dialog when you close the shutters. So if the Doppels don't reveal themselves (or if they truly are your neighbor) and you close the shutters they can plead for you to not call the D.D.D.!