This is the most amazing game I've played in a while, let alone the fact that it's a demo!
The art is absolutely gorgeous and I love the technique mentioned above. The colors were amazing and weren't hard on the eyes or overly desaturated. The mood was amazing and the visual effects were done so incredibly well and actually look very professional. I especially loved the feedback when you push the buttons all the way to the right of the map.
The sound was also done amazingly well. The music is absolute perfection and contributes to the mood in such a positive manner. I could listen to the menu music alone for hours. It gives me chills with how good it is. The sound effects are satisfying and really make the character feel like a part of the world.
As for the story, I was very engaged the whole time with every aspect, despite just being a delivery. Seriously, you did well making that enjoyable and engaging. I loved the aspect of the other side, the human appearing around, and that you could find various human objects throughout the areas. And you set up all those mysteries beyond well! What's in the package? Who's the girl? Who's that taking the package? I'm dying to know the answers and you did awesome at giving them to us not all at once and making them believable for the world at the same time.
Now on to what I hope will be good feedback to make this a better game for the full version!
One thing I might say is to find a way to incorporate the text you see at the beginning and end of the demo into the gameplay or dialogue itself. I believe this would help with engaging players. Another thing I think would make the world feel more alive would be to make the music more intense for more intense sequences. An example would be when the Observer panics when you say you left the package behind. I think it would be cool if there was a little theme that played whenever the girl was on screen, too.
I encountered two bugs, one I got when I rode over to the Terminal. The screen faded to black and stayed that way. The other time, I was entering the Science Workshop and I was unable to use any controls in the game. The controls, menu, none of them worked. Both of these only happened once, though.
Of course, all the feedback is 100% my own and might not reflect your own desires for the game. These things, in my opinion would make the experience better, but the absence of them doesn't make it worse. Sorry I've written so much! I just had a lot to say. This demo is the coolest demo I've played in a while and I can think of no games that have intrigued me as much as this one has right from the start!