The post-apocalyptic young adult fantasy flick “Mortal Engines” rolls into and out of one’s consciousness like “traction cities” that roam its landscape. There are so many aviation goggles and large gears grinding that it’s basically “Steampunk: The Movie.”

It starts out at a very high level of steampunk, then manages to go up even from there. We’ve got “old tech” and waistcoats a-plenty, hot air balloon cities galore.

Bowler-hatted royal guards? We’ve got 20. But who cares, no big deal, there’s a whole lot more. …

“Lord of the Rings” team of Peter Jackson, Fran Walsh and Philippa Boyens have tackled Philip Reeve’s 2001 book of the same name, with director Christian Rivers making his directorial debut. There’s not much setup for the dystopian future — except there was a “Sixty Minute War,” the Earth’s crust was somehow shattered into thousands of pieces thanks to some kind of nuclear-type weapon called a Medusa, and now all the cities and towns of the world sit atop giant tractor treads, traveling around and eating other smaller towns for “resources” as their citizens hoot and cheer.

“Mortal Engines” asks you to just go with it, so, yeah, we’ll just go with it.

Rivers has been working in the art and visual effects departments with Jackson and Co. since “Dead Alive” in 1992, and his sense of visual acumen is extraordinarily imaginative and huge in scope.

The designs of the cities and their inner workings are remarkable, with a sense of industrial beauty. London, a big, brutish thing with St. Paul’s Cathedral sitting on top like a little hat, motors hither and yon, munching up tiny Bavarian mining villages while its dapper residents maintain museums filled with artifacts of the ancient times, like toasters and smartphones.

Puckish museum assistant Tom (Robert Sheehan) has his world thrown topsy-turvy, literally, when he’s tossed into a giant waste tube with Hester (Hera Hilmar), a mysterious girl. She makes a dramatic attempt on the life of Thaddeus Valentine (Hugo Weaving), London’s most powerful energy tycoon.

Tom, who’s never been off London, is caught up in Hester’s quest for vengeance, as well as her escape from a killer robot skeleton named Strike. The pair are scooped up by anti-traction activist Anna Fang (Jihae) and enlisted into the resistance, housed in a city in the sky made up of biplanes, balloons and rickety scaffolding.

The sheer size and beauty of “Mortal Engines” is transporting. Even the predatory London is high-tech and well-dressed. And Anna’s crimson plane, seemingly crafted from wood and paper, is jaw-dropping.

There is so much that’s pleasing to look at, from the costumes to the characters, to the sets and landscape. It’s hard to imagine the execution, with a near-seamless blend of practical sets and computer-generated spectacle.

One just wishes the same level craft went into the characters and script.

There’s not a lot of stake in the outcomes of any of the characters, and the script is laden with clichéd old chestnuts that start to get as rusty as the crunchy engines.

The only real lessons seem to be “don’t do war” and “robots have feelings, too” (a strange tangent).

Visually, it’s busy, hefty and propulsive, but emotionally and thematically, it’s as light as air. These engines could have used a bit more in the tank.

“MORTAL ENGINES”

**

(PG-13, 2:08)