“ I don’t doubt that many viewers will simply not be up for the mental gymnastics it takes to get through this movie. But for nerds of a certain kind—lovers of hard science fiction and puzzles, science geeks and brainiacs of the sort depicted in the film—Primer not only welcomes but requires multiple viewings, and Carruth has insisted that all the information that people need to work the story out is there.
The New Cult Canon: Primer | The A.V. Club