If there was ever a genre to attract big ideas and twisty plots, it's science fiction. But what are some of the most confusing films of the bunch?
It can be a blessing and a curse, as the "McGuffins" of sci-fi open the door to explore stories throughout time and space in a million different ways—or even just tell a tale that takes place entirely in a computer or somebody's head.
The latest sci-fi epic to push the boundaries is the Wachowskis' Cloud Atlas, opening this weekend with dozens of character and storylines stretching across centuries.
But before you check that one out, stretch your mind a bit with some of these sci-fi brain busters.
[Warning: Spoilers ahead!]