"Primer" was certainly not the best film screened in competition at the 2004 Sundance Film Festival—nevertheless, it won the Grand Jury Prize—but in terms of its minuscule $7,000 budget, its super-intricate sci-fi storyline carried out with a minimalist style, and its writing-directing-cinematography-editing-composing debut of Shane Carruth, it is an undoubtedly accomplished coup.

The film also isn't for everyone, Carruth's almost insistent denial of spoon-feeding or even breaking down its plot developments for audiences wavering somewhere between amateurish art-house pretentiousness and invigorating masterly bravado. It can be assured that no one seeing "Primer" on first viewing will be able to fully understand what is going on at all times, a trait that will immediately put off those who want answers rather than questions, and frothy entertainment over heady, attention-demanding storylines, in their cinema-going. Because "Primer" is anything but typical, and because multiple viewings do seem as if they would be valuable for clarifying elements within its constantly shifting time frames and densely intellectual speak, the film holds a peculiar, albeit unconventional, value to its progressive incomprehensibility.

The premise, so much as can be deciphered, concerns four aspiring entrepreneurs out to create an invention that will knock the socks of their clients. In their work, two of them, best friends Aaron (Shane Carruth) and Abe (David Sullivan), inadvertently create two elongated boxes capable of time travel. They hide their creation in a private storage facility and begin to test it out, the amount of time they spend inside the self-made time machines—a few hours at a time—precisely equaling how far into the past they travel. Although they believe they have worked out every detail in getting away with it without upsetting the world's time continuum, they soon get in over their heads as they are faced with multiple versions of themselves within the same time paradox.

So far, so good, and there is a strange, fascinating logic to the opening half of "Primer" that makes one almost feel quick and canny to be understanding the how's and why's of Aaron and Abe's circumstances in traveling to the past. Things eventually take a turn for the even more complex and nightmarish, to the point where some plot particulars can be figured out with some thought while others must be thrown to the wayside in preference of simply marveling at writer-director Shane Carruth's nutty ambition. Trying to decipher every last development while it is occurring will frustrate the viewer, and so it is best to simply admire the maker's indelible vision. Carruth's script has been so elaborately constructed, transcending the comparatively simple handling of similar time travel themes in such pictures as "Back to the Future" and "The Time Machine," that he should be commended for proving he is probably smarter than anyone watching his first feature. At the same time, there is a certain stubbornness to his not even attempting to help the viewer out at any point that occasionally feels pompous.

Very little is learned about protagonists Aaron and Abe throughout—they work for some kind of entrepreneurial business, and Aaron is married to the patient Kara (Carrie Crawford)—and yet as the chips stack against them and their actions become potentially disastrous to the entire world, they gain a certain sympathy. This is key in involving the audience and allowing them to buy into the simultaneously fantastical and rational story.

"Primer," like the recent "IHuckabees" but maybe even more so, defies a simple explanation, and no amount of description can really do justice to the experience of watching it for oneself. The film is nowhere near perfect, with certain first-time filmmaker calling cards evident, including mediocre acting and stilted dialogue, but it is certainly engrossing as it weaves its twisted, unchronological narrative. Whatever its flaws, "Primer" may be the most intellectually demanding motion picture of the year. Some will find their mind satiated. Others will leave angry. In one way or another, all will be baffled.