One problem with modern horror is that it rarely has a sense of humor about itself—or if it does, the best it can do is point to its own self-awareness with a wink and a nudge, as if awkwardly apologizing for its own existence. Writer-director Jane Schoenbrun’s Teenage Sex and Death at Camp Miasma, premiering here at the Cannes Film Festival, breaks that cycle without breaking a sweat: it’s funny, charming, even breezy at times. And if there’s any justice in the world of movies—there isn’t