A vast grown-up play space — from the folks behind Panera and Eastern Standard — is opening at Natick Mall

Level99 opens Monday.Suzanne Kreiter/Globe Staff

NATICK — The biggest challenge at Level99, a new entertainment complex for grown-ups opening at the Natick Mall on Monday, might be describing exactly what it is.

It was dreamed up by brains from Panera, Disney, Eastern Standard, and Night Shift Brewing, but even they struggle to define what goes on inside this vast sensory funhouse of apocalyptic obstacle courses, mind-melting puzzles, and “crushable” IPAs.

“What it is, is unique and creative and different,” said Ron Shaich, Panera’s founder, who funneled $12 million into the project. “I still can’t find the right words to describe it,” said restaurateur Andrew Holden, an Eastern Standard alum who’s in charge of a menu that includes slow-cooked short rib and “umami-bomb” salmon.

Level99 is the latest entrant in a growing category of venues that go beyond the hip bowling alley or urbane game room. It’s high-end food and high-intensity activity. One company calls it “competitive socializing” — and Level99 is Greater Boston’s most audacious effort yet.

Even Matt DuPlessie, the MIT-trained engineer who said he conceived of Level99 in a dream, acknowledges the challenge of describing his new venue in a sentence. “You have your work cut out for you,” he told a reporter while offering a tour of the space.

An arena game area at Level99, a new entertainment complex for grown-ups opening at the Natick Mall on Monday.Suzanne Kreiter/Globe Staff

Challenge accepted: Level99 is what would happen if you held a MENSA meeting on an “American Ninja Warrior” course in what used to be a Sears store.

It’s 48,000 square feet, with a ninja room, an Aztec temple, and a ropes course traversing LED lava, among other challenges both physical and mental. It has fancy cocktails, lamb meatballs, and Detroit-style pizza for when you need a break to strategize.

And perhaps most importantly, Level99 is an entertainment concept that might be uniquely suited to this moment.

The pandemic has decimated brick-and-mortar retailers, leaving massive holes in suburban malls where anchor department stores used to thrive. Now, entrepreneurs are moving into those spaces with concepts intended to serve people craving new activities both for social and corporate events.

“We’re seeing it with shuffleboard. We’re seeing it with darts. Even ping-pong,” said Susan Walmesley, chief marketing officer at Puttshack, “an upscale, tech-infused mini-golf experience” that will open next year in Boston’s Seaport. “More and more people want to be doing something when they go out, not just having a drink.”

Previous waves of large-format entertainment-oriented retail have come and gone, from arcades to laser tag to the food halls and movie theaters that anchored big new developments all over Boston before the pandemic.

And the latest round of projects requires unproven businesses to take out long-term leases on big, expensive, spaces that could be difficult to afford if the novelty wears off.

Shaich said he’s convinced the market for Level99 is there, and he’s confident enough that he now owns half the business. He compared Level99 to Panera, saying it’s another unique concept that will define an entirely new category. Fast-casual dining, to which Panera was an early entrant, is now a $60 billion industry.

“It’s not Chuck E. Cheese on steroids, and it’s definitely not Dave & Buster’s,” he said (although it is physically next-door to one of the arcade’s franchises). You can play video games at Dave & Busters. You feel like you’re inside one at Level99.

And unlike a trampoline park or an escape room, Level99′s challenges will keep changing.

Level99 backers hope working with Night Shift and alums from Eastern Standard will draw suburbanites who used to live downtown — even if the business is in a mall mere steps from a Sbarro.

The Nightshift Brewing Taproom at Level99.Suzanne Kreiter/Globe Staff

There are more experiments like this coming, predicted Mike Kelleher, head of specialty leasing at Federal Realty Investment Trust, which owns Assembly Row in Somerville.

“People got very imaginative during the pandemic,” he said. “These kind of venues can be really interesting for shopping centers. We’re going to see a lot more come out.”

Puttshack, for instance, recently leased roughly 25,000 square feet at the Echelon complex in the Seaport. That’s enough for four indoor mini-golf courses, plus a large bar that will serve fancier food than your typical putt-putt snackbar.

On a slightly smaller scale, there’s PKL Boston, the brainchild of a pair of enthusiasts of pickleball, a fast-growing sport that fans compare to badminton with a wiffle ball, or ping-pong on a tennis court.

They’re opening a pop-up at Assembly Row this summer and have leased 21,000 square feet for a permanent location at an as-yet-undisclosed spot in South Boston, which will open next year.

“It’s where the competition of sports meets your favorite hangout with your crew,” she said. “Just good vibes, good food, and good drinks.”

Good vibes are great. But Level99 has even bigger aims.

DuPlessie’s resume includes a stint doing billion-dollar theme park build-outs at Disney’s Animal Kingdom hotel and Star Wars: Galaxy’s Edge.

Now his Norwood company, Box Fort, builds interactives for museums and theater productions. They also conceived each of the challenge rooms and whittled 2,000 original ideas to the 43 that made the cut.

The rooms are designed to be difficult — and yes, they’re both frustrating and fun — and would take over 30 hours to complete.

At $29.99 for two hours, Level99 is more affordable than many theme parks, and more hands-on than a museum. There’s also beer. And lots of technology. RFID bracelets give visitors access to rooms and keep track of their points. That data also inform designers what challenges are the most difficult and the most entertaining.

One of the challenge rooms at Level99.Suzanne Kreiter/Globe Staff

“We really think about Level99 as a data company that’s trying to figure out what fun is,” DuPlessie said.

He and Shaich hope their Natick location will be the first of many, a chance to create and shuffle challenge rooms from one venue to another to keep the experience fresh.

”I just love to make environments that feel magical. You have the chance to do things that maybe you’ve watched on TV or you’ve played in a video game, but feel like they couldn’t possibly be real,” he said. “And I like to make them real.”