The young director Tze Chun is not a flashy filmmaker, but he understands the vulnerability of immigrant workers in the sleazy sub-rosa economies of a floundering 21st-century America. Tze has lived that life, and observes it with acuity in this straightforward tale of Raymond and Tina (played by the enchantingly solemn Michael Chen and Crystal Chiu), two Asian children trying to look after themselves while their single mother (Cindy Cheung) becomes embroiled in an illegal Boston pyramid scheme that leaves the undocumented family equally exposed to exploitation by some who mean well—and others who don’t. Children of Invention was edited (on her living-room floor) by Anna Boden, co-director with Ryan Fleck of Half Nelson and Sugar, and Tze’s movie is infused with the same quality of (mostly) unsentimental mercy, and the same sensitivity to the way in which being placed at risk without basic rights invariably breeds more and more risk. In the children’s creative response to their apparent abandonment we see—only a little wistfully—the capacity of kids to fashion a viable world out of the materials available, as well as a rueful homage to American dreams both wonderful and warped. As a bonus, there’s no spurious uplift.