YOUTUBE IS BURSTING at the seams with horror shorts, the vast majority of which traffic in the same old jump scares and photoshopped demon faces. David F. Sandberg’s Lights Out, however, managed to distinguish itself from the lurching masses, brilliantly capitalizing on its limitations to present one indelibly shivery concept: namely, a silhouette that creeps closer whenever the lights go off. The James Wan-produced feature-length expansion can’t match the compressed primal frisson of the original, but it contains more than enough flickeringly lit yelps to justify its existence. How many variations can be successfully run on the same gag? Quite a few, as it turns out.

Cribbing heavily from both The Ring and Cronenberg’s The Brood, Lights Out’s set-up focuses on a mentally disturbed mother (Maria Bello) with a distressing habit of carrying on extended conversations with a dead childhood friend. What’s more, said friend has a tendency to ferociously shred anyone not standing directly below a 1,000-watt bulb. Making his feature directorial debut, Sandberg does competent work between the jolts, dispensing exposition at a rapid clip and getting a refreshingly non-precocious performance out of Gabriel Bateman, as Bello’s perpetually endangered young son. His film’s biggest pro and con, actually, might be Bello, who delivers a tremendously effective mix of pathos and selfish fury. She’s so good, honestly, that her tremulous presence threatens to throw the rest of the movie’s agreeable Velveeta sheen out of whack.

Whenever she takes a powder and the shadows fade up, though, Lights Out finds its true calling as an efficient, occasionally ingenious scare machine. Utilizing seemingly every light source known to man (the bit with an erratic neon sign is especially nice), Sandberg concocts a steady array of enjoyable oh-shit moments, chock full of opportunities for his murderous ghoul to move in and out of the visible spectrum. If you’re a horror fan, this will get where you want to go.