The best effects are often the simplest.

Especially in horror. Particularly in “Truth or Dare,” the latest spin on “It Follows,” the horror trope that you pass on your curse to somebody new just so you can survive.

Here, it’s that killer Joker Smile that victims see or paste on themselves as they’re playing “the game.” A little makeup or glue, a bit of lighting, an added dab of digital Satanic red in the eye — you’ve got yourself a murderous threat asking the life-or-death question, “Truth or Dare?”

Yeah, that’s pretty much ALL the team of writers and director Jeff Wadlow have going for them. But not every Dead Teenager movie can be “It Follows” or “Final Destination.”

Six college friends and a nerd tag-along spend spring break in Mexico. Cute “Miss Moral High Ground” Olivia (Lucy Hale of “Pretty Little Liars” and “Scream 4”), the one who’d rather be building houses for Habitat for Humanity, picks up a bearded, chivalrous stranger (Landon Liboiron) who suggests a little after-hours drinking at an abandoned mission church. 

Hey, why not play a little “Truth or Dare?” They start, and that’s when Carter the stranger is tasked with a truth that will change all their lives, and end most of them. He’s lured them there to take a curse off himself, or at least better his odds.

“Tell the truth or you die. Do the dare or you die. Refuse to play? You die!”

It’s not until they get back to school that they start seeing people smile that smile, hearing people make that murderous challenge. It takes minutes to get everybody on board, but once enough of them have had the visions, and one or two of them die, the rest team up to try and survive.

Olivia’s relationship with BFF Markie (Violett Beane of “The Flash” and “The Leftovers”) is strained. So much for their pledge, “Between you and the world, I choose you.”

A boy comes between them. Some survive their first challenge, others don’t. Count them down — seven, six, five, four…

That’s where the tedium sets in. The truths get more lame, the dares less creatively deadly. A gay kid (Hayden Szeto) has to confront his homophobic cop dad, and amazingly, that’s played out OFF camera. The feud between Markie and Olivia feels arbitrary and weak.

And still the movie goes on, grasping for a conclusion that feels as if it was workshopped in a college course — correspondence school maybe.

Such Blumhouse Horror productions have the most generic of casts, as if they think the audience won’t notice the undersold emotions, the failure to properly register shock when confronted with the supernatural.

That’s the difference between “A Quiet Place” and “Truth or Dare” kids — the kids. And the adults. They’re emotive, empathetic actors who reach out and connect with the viewer, at least in John Krasinski’s blockbuster.

Cut-rate horror like this, they’re just girls in revealing outfits and boys drooling after them — until the next coed gets killed. Preferably after her big make-out scene.

MPAA Rating: PG-13 for violence and disturbing content, alcohol abuse, some sexuality, language and thematic material

Cast: Lucy Hale, Tyler Posey, Violett Beane, Sophia Ali, Landon Liboiron, Nolan Gerard Funk, Sam Lerner, Hayden Szeto

Credits:Directed by Jeff Wadlow, script by  Jillian Jacobs , Michael Reisz, Christopher Roach. A Blumhouse/Universal release.

Running time: 1:40