If a movie has you cheering when the heroine socks a little kid in the face, it’s probably black comedy. At least I hope so.

Such a moment comes in “Ready or Not,” a violent slice of slapstick that takes a quirky idea and runs like the devil with it. The result has a cynical, unhealthy appeal.

Our protagonist — and the only sane person in view — is Grace (Samara Weaving), who feels a little overmatched. It’s her wedding day, and groom Alex (Mark O’Brien, from “Arrival”) comes from an extremely wealthy family.

The ceremony is at the old family estate. But instead of enjoying the usual nuptial evening, Alex announces that according to tradition, newcomers to the dynasty must play a little game in the mansion at midnight. (The family fortune comes from a long history of making games.)

Luck will determine the game itself — maybe chess, maybe backgammon. Sadly, the game tonight is hide and seek, which translates in this household as “Kill the Bride.”

That’s right: Grace must now elude the murderous reach of her new in-laws, who will try to hunt her down using a collection of antiquated weapons. The current patriarch (Henry Czerny) and his wife (Andie MacDowell, nicely deadpan) are convinced that if they don’t kill Grace by dawn, the entire clan will die.

Comparisons to a live-action version of the boardgame Clue are relevant here. Curiously, the movie makes no reference at all to video or online games, as though existing in an alternate universe.

“The rich are very different,” says Alex’s brother (Adam Brody). He’s quoting F. Scott Fitzgerald, explaining the peculiar habits of his class. The film hints around at “Get Out” territory — that is, trying to add a little social critique about toxic privilege to its scare show — but this is not much more than frosting on the poisoned cake.

Directors Matt Bettinelli-Olpin and Tyler Gillett lay on plenty of snark as they trot through the lethal proceedings. The movie’s got no soul, just a jokey series of gory shocks — but the thing never stops moving, and thankfully doesn’t rely on the heroine doing stupid things just to keep it going.

The cast is fun, too. Samara Weaving is the niece of the great Aussie actor Hugo Weaving (memorable for his “Matrix” and “Lord of the Rings” roles), and she’s got a slyly funny delivery that keeps us on Grace’s side.

Brody, a good source of sarcastic one-liners going back to his days on “The O.C.”, actually gets to dig out a little pathos as the most conflicted member of the family. “Wynonna Earp” star Melanie Scrofano is suitably manic as a coke-snorting sister, and Nicky Guadagni is super-creepy as a very ominous auntie, whose elegant manner belies her head-chopping skills.

Positioned as a little late-summer sleeper, “Ready or Not” shouldn’t be over-praised. This film does its job, delivering bloody laughs and sending the upper crust to Kingdom Come — good enough for the dog days of August.

“Ready or Not” (3 stars)

A cynical little black comedy about a bride (the slyly funny Samara Weaving) surprised to learn that her extremely wealthy in-laws have planned a survival game for her — if she can live through her wedding night, she can stay in the family. The violent slapstick is effective, the “Get Out”-style social critique not so much. With Adam Brody.

Rating: R, for violence, language

Showing: Alderwood, Alderwood Mall, Cinebarre Mountlake Terrace, Everett Stadium, Galaxy Monroe, Marysville, Meridian, Oak Tree, Pacific Place, Seattle 10, Thornton Place, Woodinville, Cascade Mall