it's a pinhole movie project where an apartment is darkened but for a hole in a window, letting a little bit of light in. then, voila, the outside world projects upside down on the walls (camera obscurafor those of you who aren't familiar with it's principle). camera obscura was what ultimately led to photography (and eventually film making), and it's interesting to see a movie project using the elements of its roots.
watching this video made me want to make myself a pinhole camera. hey, maybe that'll be my next project!