It's been a while since a science fiction movie was so complex. An idea can shape the world? That's no doubt true. To take the metaphor to its logical limit, Inception (dir Christopher Nolan, 2010) shows in extraordinary and exhausting detail how, in an alternate universe to ours, an idea can be implanted in a man's mind by others - through his dreams. Or other people's dreams, even. In the case of this movie, there are several dreams running concurrently. At each level in the dream architecture there's another task to achieve, another hurdle to surpass, another puzzle to unpick. Another fight to win.

The underlying concept that supports the plot is foreshadowed early on in the movie when Cobb (Leonardo Di Caprio) is still trying to conscript Ariadne (Ellen Page) to become the architect of a set of worlds where Cobb will take Robert Fischer (Cillian Murphy), the son of a wealthy energy baron, in order to plant the idea that Fischer should dismantle his father's business empire. Cobb has been asked to do this by Saito (Ken Watanabe), who wants to ensure that the Fischer enterprise is kept in check so that it does not develop into an unmanageable monopoly with more power than civil society or the political apparatus can control.

Ariadne foreshadows the movie's plot concept by placing opposite one another two large mirrors, in which the reflections of each are repeated into infinity. What is real, is the implied question. Where does the dream end and reality begin?

The reward for Cobb, who must solve the puzzle of Fischer's dreams, is that he gets to reenter the United States, where his children live. His dead wife had implicated Cobb in her death by hiding her madness immediately prior to her suicide. How did that madness begin? The plot must progress a fair way before that secret is revealed. By that time, Cobb and his band of dream-deceivers have descended several levels into Fischer's subconscious, battling hostile "projections" at each step with wit and weaponry, as they attempt to plant the seed that will deliver Cobb into the arms of his children.

There are rules in dreamworlds, just as there is gravity in ours. They are interesting and necessary to understand in order to appreciate the drama the plot generates, but they are not otherwise profound. Time, for example, flows slower at each successive step down into the target's subconscious you travel. Events at the superior level can influence the environment in lower levels. Beyond these small details there is nothing, however, that too closely resembles art. There is nothing to overly disturb the viewer intent on enjoyment. The thing that comes closest to art is that Fischer's father dies in Sydney: shades of Murdoch, perhaps? It's a Disney film, after all.

This is a small-concept movie with a large budget and plenty of fast action for the young-at-heart. Its curious notions of time and space will no doubt make many people think, but the essential form of the movie is not all that interesting. If anything can be "taken away" from the film it is that we construct our own realities, and that our dreams are important. But the ultimately too-complicated mechanics of the screenplay militate against any more subtle suggestions that might move toward a greater purpose. It's a fun flic but also a pretty conventional one.