Skinamarink is a clear depiction of what it feels like to be left alone in the dark as a kid.
The exaggerated use of Grain adds to the effect our eyes have when we're in a pitch dark room. This is where our mind start to see things that are not really there...
The film is successful if you let it and it begs its viewer to be creative. You have to really invest your attention to every second of the frame if you want to feel what the filmmaker is trying to achieve.
It's not a film for everyone but it's definitely one of the best horror/thriller films I've ever seen.