Really, really good. This really hits the spot visually, sound-wise and puzzle-wise. It is indeed quite tricky, for me at least, but up until now I could (almost) finish them myself, only saw the meaning of the painting on the wall of the second room below in the comments, but probably would've figured that one out at some point. I think ;-) So, even if it seems a bit too tough for me now, it does feel realistically difficult, so again, well done!
The camera and notes features are very well executed as well. One improvement would be to be able to look at your notes, while at the same time being able to see the world, so you don't have to flick back and forth.
Edit: Completely edited this message because I got a few steps further, rendering the most of this message useless ;-)