When we first meet Moses (John Boyega), the aptly named leader of a South London street gang and the hero-protagonist of British writer-director Joe Cornish’s feature-length debut, Attack the Block, he’s forcibly separating Sam (Jodie Whittaker), a young nurse on her way back to the low-income apartment from her cash, watch, and other valuables. From just a few words and body language, it’s easy to see why Moses’ crew respects and admires him. Moses and his crew, Dennis (Franz Drameh), Jerome (Leeon Jones), Biggz (Simon Howard), and Pest (Alex Esmail), aren’t hardened criminals, at least not yet. They’re still in high school. They still live with their parents or other near-relatives. They’re misguided, probably bored, maybe even desperate to escape the socio-economic deprivations of block life, but they haven’t crossed over into hardened criminality.

In mid-mugging, a meteorite slashes across the night sky, narrowly missing Moses and his crew, and destroys a car parked nearby. Sam uses the opportunity to escape. Moses, fearless and foolish in equal parts, approaches the smoldering, demolished car, hoping to abscond with a radio or other electronic device.

What Moses doesn’t realize, however, is that the meteorite isn’t just a space rock. It’s the chosen means of transportation for an invasion from outer space. Moses tussles with the meteorite’s ferocious, if diminutive, occupant, tracking it down to a nearby shed and killing it. Moses carries the dead alien around like a trophy (the better to increase his street cred). But the dead alien proves to be only the first of many. New aliens, larger, hairier, and equipped with glow-in-the-dark canines emerge from the next wave of meteorites.

Sam eventually crosses paths with Moses and his crew again, first reluctantly, when Moses forces her to treat Pest’s injured leg and later, after Sam narrowly escapes an encounter with the aliens. Although the aliens pose the biggest risk to life and limb, Cornish includes Hi-Hatz (Jumayn Hunter), a mid-level drug dealer eager to bring Moses into his crew to run drugs for him, as an increasingly dangerous antagonist, adding Ron (Nick Frost), a drug dealer in Hi-Hatz’s employ, Brewis (Luke Treadaway), a trustafarian pot-smoker/dealer caught in the wrong place and the wrong time, and pint-sized wannabe gangbangers, Probs (Sammy Williams) and Mayhem (Michael Ajao), as much-needed, if occasionally disturbing, comic relief.

Cornish, whose background is in television/radio and feature-film writing (he co-wrote the forthcoming The Adventures of Tintin with writer-director Edgar Wright), ably balances Attack the Block’s disparate genre elements and influences, seamlessly switching from naturalist crime drama to alien invasion flick to pot comedy and back again. Cornish isn’t afraid to mix in social commentary between the ever-escalating action beats. If Attack the Block is any indication (and it probably is), Cornish clearly falls on the nurture side of the nature vs. nature debate. Given the chance, Moses and his crew prove themselves resourceful, courageous, and even heroic in the face of overwhelmingly dire odds. Of course, it takes an alien invasion to force Moses and his crew to wake up to their inner, selfless heroes.

It’s to Cornish’s considerable credit that even when he stumbles, as when he repeatedly underlines Attack the Block’s simplistic central theme, “Actions have consequences,” through dialogue, he ensures that consequences, sometimes bloody, sometimes gory, almost always unmerited, follow misguided and/or selfish actions. Those consequences only matter because Cornish gives his ensemble cast enough character shading to remind us of their characters’ young age and inexperience, the better to make moviegoers feel the tug on bloody heartstrings when one (or more) member of Moses’ crew fails to make it to the next scene.

That Cornish’s street punks-turned-heroes are, at times, difficult to decipher due to heavily inflected British accents and slangs isn’t a fault or flaw. Attack the Block was made for British audiences first, international audiences second, but a combination of effort and concentration should be more than enough to get you through the first 15-20 minutes of Attack the Block’s running time. By then, you’ll either figure out the dialogue or you won’t care because you’ll be completely immersed in Attack the Block’s many charms.

Rating: 3.5 out of 5 stars.