With the help of some deft karate chops, a well-placed fireball hurled at ferocious villains and a set of 3-D glasses, Legoland California is hoping to upend the hypercompetitive world of theme park attractions — for now.

The 4-D dark ride Ninjago, the Carlsbad park’s latest Lego-inspired attraction, is the first in North America to use hand gestures in place of physical devices to control the outcome of the action — in this case an epic ninja warrior battle. Sensory effects like heat, smoke and wind enhance the 3½-minute virtual journey through skeleton-filled caves and lava streams.

Disney’s Toy Story Midway Mania may have its pie- and egg-throwing cannons and Knott’s Berry Farm’s Journey to the Iron Reef its freeze ray guns. But Legoland now has what some say is an even more powerful marketing boast.

Taking a page from controller-free video gaming — think Xbox Kinect — Legoland California and its parent company, Merlin Entertainments, are trying to wow a whole generation of youngsters hooked on mobile devices and high-tech games. The strategy also squares well with theme parks’ growing enthusiasm for interactive elements.

“It’s inevitable we’d see this type of technology in the theme park world, so Legoland is now ahead of this,” said Robert Niles, editor of Theme Park Insider. “This allows them to say we’re the first on this one and gives them a good connection with the younger kids.

“Right now, this is the new thing, but at some point it becomes the old thing, and you’ll want to do more with this than waving your hand above the lap bar.”

Warriors in training

Ninjago, inspired by the popular Lego line of Ninjago toys and a related TV series, owes its hand-gesture feature to Trio­tech, a Montreal company that pioneered what it’s dubbed the Maestro technology. It will be incorporated into rides at all of the Legoland parks.

Youngsters and their parents, seated in four-person vehicles and wearing 3-D glasses, are instantly immersed in the Ninjago story line as motion-sensing technology embedded in the lap bars detects hand movement above it.

Intended to be warriors in training under the watchful eye of Ninjago character Master Wu, riders are challenged to vanquish a legion of enemies, from snake tribes and ghosts to skeletons. Using hand movements, guests hurl virtual, color-coded projectiles — fire and ice balls, spheres of lightning, and shock waves — at animated creatures that appear to jump out of 30-foot screens.

Along the way, special effects like dangling spiders, skeletons popping out of a barrel and bees emerging from a hive enliven the action.

The adventure culminates with the Great Devourer, a monstrous snake that explodes in a huge flash of green after a barrage of virtual artillery fired by hand-waving, karate-chopping riders.

All along the way, a dashboard in the vehicle tracks the players’ scores, as they compete with friends and family members.

“This is all in 3-D, so the guest really has the impression that the projectile comes out of his hands,” said Triotech Vice President Christian Martin. “Secondly, everything happens in real time. Nothing is pre-rendered, so this makes the guest an integral part of the adventure and not a passive observer.”

The ride is part of a new 1-acre attraction called Ninjago World, which re-creates an Asian-style temple and a shop selling merchandise. A large courtyard is an interactive playground of sorts, with a rock-climbing wall, spinners to test youngsters’ agility and a monastery fashioned from 850,000 Lego bricks, which kids can embellish with their own Lego creations.

A new paradigm

With the recent debut of Universal Studios Hollywood’s Wizarding World of Harry Potter and Disneyland’s ambitious plans for a Star Wars land, Legoland California General Manager Peter Ronchetti acknowledges that the park needs to keep pace with rapidly changing innovations in the theme park and home entertainment arenas. He won’t reveal Ninjago’s price tag but says it represents the park’s biggest investment yet in a ride.

“This is really the start of a new journey for us as a business in [connecting] the physical bricks with the new technology,” said Ronchetti. “I think there will be quite a few more steps to take, and it’s a technology that’s developing very fast. We’ve broken into that world very early. Ten years ago, this technology wouldn’t have been available at any cost.”

While interactive attractions have become de rigueur for theme parks, it’s only in the past year or two that the technology has measurably improved, said Daryl White, president of Cavu Designwerks, a year-old attractions company.

“It’s a very big issue with theme parks now to provide an experience guests can’t have at home,” he said. “If you have all these people playing Halo for hours in their basement, what is going to draw them off their couch and into a theme park?”

The latest, greatest thrill-inducing roller coaster still holds a hallowed spot in today’s theme parks, said industry consultant Dennis Speigel, but they, too, are being retrofitted to become more interactive.

As an example, he pointed to the nine Six Flags parks where riders will be able to strap on virtual reality headsets offering 360-degree views and action synchronized to the movement of the coaster.

Triotech CEO Ernest Yale agrees that the new technology won’t necessarily displace the traditional amusement park ride but elevate it to a new, immersive experience.

“When you look at rides that are not interactive, you’re transported to a virtual world, but now you can be part of the story, you can have a score, succeed or fail, and there’s a competitive aspect where kids can try to have a higher score than their friends,” said Yale, whose company has 225 attractions in more than 50 countries.

“In the next few years, there will be a lot of new things that come out, and we’ll find out what kids like. It’s like a new paradigm for amusement parks.”