Lost the plot: From Donnie Darko to 2001: A Space Odyssey - getting to the bottom of those puzzling and playful brain-teasers

Did you get it the first time around? It's 20 years since Richard Kelly's Donnie Darko received its world premiere at the Sundance Film Festival. The film - a complex and, occasionally, impenetrable sci-fi, starring Jake Gyllenhaal as a miserable teenager obsessed with time travel - left critics and audiences dumbfounded.