Primer

“What happens if it actually works?”

Aaron (Shane Carruth) and Abe (David Sullivan) spend their evenings in a garage with a few other engineers, building devices on the side to see what might sell. One of the machines produces an effect none of them planned for, and they start using it to play the stock market. Carruth made the film himself, and it asks you to keep up with the plain fact that every choice you make in a story like this has a cost.