By Mark Kennedy, AP Entertainment Writer

There's always that moment on roller coasters when the lap bar gets locked down and you slowly, agonizingly ride up to the first drop. You know the next few minutes are going to be harrowing — you just don't know how bad. So here's a warning about the new animated amusement park film "Wonder Park" — it's going to be more harrowing than you can imagine.

A simple, bucolic beginning with the sunny characters exuberantly crying "Splendiferous!" leads to a post-apocalyptic, violent middle that includes killer plush dolls, deadly giant robots, lava and existential crisis. It then ends on a sickly sweet note. The tonal shifts alone are enough to make you want to hurl.

The cynicism and ultra-violence of Paramount's "Wonder Park " undermines some top-notch animation, which includes astonishingly realized things like matted fur on a boar, lifelike potholes and intricate leaves and ferns in a forest. There are roller coaster moments that will make you feel like you're on the ride yourself, gripping your seat. And John Oliver voices a rather great sassy porcupine. But the film's message of always keeping a creative light shining gets horribly lost in the darkness.

The story centers on a creative, green-eyed, red-haired girl named June (voiced by Brianna Denski) who creates in her bedroom with her mom (Jennifer Garner, sweetness and light) a fantasy park filled with cool amusement park rides and colorful talking animals. She even brings to life a makeshift version on the streets in the film's best sequence. But tragedy leads her to abandon the park, until one day June discovers it seems to have been actually constructed in a nearby forest and abandoned.

Great idea, right? Sure, until we realize this worn-at-the-edges park is now more like Jurassic Park than the Magic Kingdom. Three-quarters of it looks like smoldering Nagasaki. The thousands of adorable plush toy souvenir monkeys in June's park have turned into a swarming legion of weapon-wielding Chimpanzombies who try to drag away their screaming prey or control a giant robot that tries to crush all the cute animals. Not splendiferous.

June is flabbergasted. She asks — like you may — what's going on. "What does it look like?" says a giant blue grizzly bear. "We're at war." Thus begins what feels like hours of "Mad Max" meets "Interstellar" as June and her band of ragtag, squabbling animals — including a solid Mila Kunis and a very emoting Norbert Leo Butz — try to restart the park and banish "the Darkness," a whirlpool of dark clouds in the heavens. (You may have a fun time explaining all this in the car with your kids on the way home. But that time may be quicker than you think; at a recent screening, a few young ones sobbed and immediately wanted to leave.)

Perhaps that mention of war is a telling one for this production, which does not list a director in its credits. (The previous person at the helm, Dylan Brown, was fired due to complaints of alleged inappropriate conduct.) Another obvious sign of internecine conflict is the title — "Wonder Park" — but all the action takes place in "Wonderland," including all the park's signage and lines like this: "You are the wonder in Wonderland." Apparently, something less than wonderful was happening behind the scenes.

The screenplay by longtime writing partners Josh Appelbaum and Andre Nemec ("Mission Impossible 4: Ghost Protocol" and "Teenage Mutant Ninja Turtles: Out of the Shadows") does try new and refreshing things, like having an Indian boy as a hero — when was the last time an animated figure yelled "Thank Krishna!"? — but also leans on some cliches, including one that should've been retired long ago: The Terminally Ill Parent Whose Absence Wrenchingly Teaches Our Hero Self-Sufficiency.

"Wonder Park" has a great premise about a spunky kid engineer and a world she constructs taking flight, but takes a few too many dark loop-de-loops and crashes hard. If you pass this amusement park, skip it.

"Wonder Park," a Paramount Animation release, is rated PG for "some mild thematic elements and action." Running time: 86 minutes. One and a half stars out of four.

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