The smartest, funniest cheap monster-movie import this side of June’s Trollhunter, Attack the Block is a near-perfectly balanced seasonal trifle: Anchored in social realism yet determinedly goofy, it’s neither too eager for laughs nor overtly preachy. Set in a sprawling London public-housing compound, the film follows a group of teenage hooligans as they stumble upon and eventually thwart an extraterrestrial invasion. Led by the angry but reasonable Moses (John Boyega), the kids defend their turf alongside co-residents Sam (Jodie Whittaker), a nurse they half-assedly mug prior to the appearance of the ETs, and Ron and Brewlis (Nick Frost and Luke Treadaway), two underachievers who serve as a sort of stoned Greek chorus. Things move fast enough to distract from the movie’s paltry budget—the woolly aliens, or “big gorilla-wolf motherfuckers” as Moses calls them, are plainly guys in suits—and give the film a Lord of the Flies by way of John Carpenter feel. (Joe Cornish, the actual director, is a well-known comic actor in England.) Attack the Block strains somewhat to deliver a climactic moral, but the way it slyly shifts our sympathies to Moses and his crew (at the expense of another species, granted) without overplaying their deprivation puts more serious-minded indies to shame.