Nobody loves summer blockbusters more than we do. (We've already seen 'Star Trek Into Darkness' multiple times.) Occasionally though, we need a movie with substance rather than something filled with special effects and thunderous explosions. Intellectually speaking, it's the difference between fresh popcorn and the stuff that comes out of a microwaveable bag, you know?

But, sometimes dense, complicated movies leave us wondering,"What the heck did we just watch?" In other words, just because a flick is packed with multiple layers of meaning, that's no guarantee it'll actually make sense. So in that spirit, check out the 10 most confusing movies of all-time below.

  • 1

    '2001: A Space Odyssey'

    Warner Bros.
    Warner Bros.
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    Today, Stanley Kubrick's big screen adaptation of Arthur C. Clarke's novel '2001: A Space Odyssey' is widely viewed as a classic. But its trippy visuals, long scenes without dialogue and glacially-slow pacing make it near impenetrable to some.

    And let's not forget the film's ending, where astronaut Dave Bowman hurtles through a psychedelic kaleidoscope of colors and is then transformed into a giant space-faring baby known as the "Star Child."

  • 2

    'Donnie Darko'

    Newmarket Films
    Newmarket Films
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    Look, we love 'Donnie Darko' as much as the hipster barista with a Frank the Bunny tattoo at your local coffee shop, but you practically need a degree in theoretical physics to suss out the meaning of this cult classic.

    Luckily, a director's cut was released in 2004 that makes the twisty, time travel plot a bit easier to follow. But, we're still a little confused by the ending over a decade later.

  • 3

    'Memento'

    Summit Entertainment
    Summit Entertainment
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    Given the accessibility of Christopher Nolan's Batman films, it's hard to believe that he's also responsible for 2000's headscratcher 'Memento,' which starred Guy Pearce, Joe Pantoliano and Carrie-Anne Moss.

    The movie tells the story of Leonard Shelby as he attempts to hunt down one of the men who raped and murdered his wife. Problem is, Shelby suffers from a form of amnesia which makes it impossible for him to store recent memories. That's a great plot device, for sure, but definitely not something that lends itself to a clear narrative. To make matters worse, the story is told out of chronological order.

    Fortunately for fans, the movie was released on DVD with a hidden ability to play its sequences in order. Although, if we're being honest, this didn't help us very much.

  • 4

    'Eraserhead'

    American Film Institute
    American Film Institute
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    David Lynch is the godfather of weird and strange movies and his first feature-length film, 'Eraserhead,' is no exception. It's the highly surreal tale of a man named Henry Spencer as he cares for his mutated, reptilian child. It also includes a chicken that gushes blood, gigantic sperm cells and a strange woman with swollen cheeks who lives in a radiator.

    Although Lynch has stubbornly refused to explain the film, it could be a commentary on sexual mores, a metaphor for the fear of parenthood or simply a bad dream. Or not.

  • 5

    'End of Evangelion'

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    When 'Neon Genesis Evangelion' aired on Japanese TV from 1995-1996, it was praised by critics and fans alike for its unique visual style and compelling story in which children use mecha to battle towering monsters known as "Angels." Still, almost everyone agreed it didn't make a whole lot of sense.

    So, when creator Hideaki Anno released an expanded version of the final episodes in 1997 as a movie called 'End of Evangelion,' fans had high hopes for some much-needed clarity. Needless to say, they were left disappointed.

    In the film's final scenes, protagonist Shinji goes hopelessly insane and all of humanity dissolves into a primordial soup. Then, Shinji and fellow mecha pilot Asuka somehow emerge from the sea of human goo and the former tries to strangle the latter as a way to confirm his own individuality. Er, what? A simple Saturday morning cartoon this ain't.

  • 6

    'Primer'

    ThinkFilm
    ThinkFilm
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    There's been some serious buzz about Shane Carruth's recently-released second film 'Upstream Color,' but he started his career with 2004's 'Primer,' an inscrutable low-budget film about two scientists who build a time travel machine.

    To say that 'Primer' -- which was made on a budget of just $7,000 -- is complicated would be a massive understatement. In fact, it's so packed with details that multiple viewings are practically required. Almost 10 years after its debut, fan sites are just now unraveling its meaning. So if you plan on watching 'Primer,' you'll need to do some heavy reading first.

  • 7

    'Pi'

    Artisan Entertainment
    Artisan Entertainment
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    Like most of Darren Aronofsky's films, 'Pi' is so complicated it's guaranteed to make your head explode. It involves a mathematician named Max Cohen who becomes increasingly obsessed with the notion that everything in nature can be understood with numbers. Cohen also suffers from paranoia, hallucinations and social anxiety disorder.

    Nothing, by the way, can prepare you for the film's startling ending, which involves home surgery with a power drill. Watch this movie and you'll probably feel like you just had a lobotomy yourself.

  • 8

    'The Matrix Revolutions'

    Warner Bros.
    Warner Bros.
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    After an awesome first film, almost everyone agrees that 'The Matrix' trilogy lost steam at the end. But the third film -- 'The Matrix Revolutions' -- also qualifies as the most confusing of the bunch.

    In particular, the film's ending is a real puzzle. Does Neo die after his climactic battle with Agent Smith? Or does he become one with the Matrix? Is humanity's war with the machines truly over? And just what are the Architect and the Oracle babbling about in the final scene? So many questions and so few answers. Maybe Neo should've taken the blue pill instead.

  • 9

    'The Tree of Life'

    Fox Searchlight
    Fox Searchlight
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    On one level, Terrence Malick's 2011 film 'Tree of Life' is the fairly straightforward tale of the O'Brien clan in 1950s Texas. But then things quickly get confusing -- the family's story is interspersed with random scenes depicting nothing less than the creation of the universe, the origin of life and the destruction of the Earth after the sun goes supernova.

    Then there's the film's conclusion, which presents a vision of death and resurrection in dream-like slow motion. Um, we're sure there's a coherent movie in here somewhere, but we haven't found it yet. Bear in mind that even River Road Entertainment head Bill Pohlad, who financed the movie, once described it as "crazy." Don't say we didn't warn you.

  • 10

    'Mulholland Drive'

    Universal Pictures
    Universal Pictures
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    Along with 'Eraserhead' and 'Blue Velvet,' 2001's 'Mulholland Drive' is one of David Lynch's most critically-acclaimed works. But this story of an aspiring actress who befriends an amnesiac hiding in her aunt's apartment is anything but easy to follow.

    In fact, it's non-linear, disjointed, packed with seemingly unrelated sequences and highly open to interpretation. (The ending in particular has been the subject of much debate.) And as you might expect, Lynch won't explain what it's all about. If anybody figures out what's up with the creepy figure behind Winkie's Diner, please let us know.

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