Mightier, a Boston Children’s Hospital spinout that makes biofeedback video games to help children with emotional regulation, has raised $2.4 million in seed funding. Slow Ventures led the round, with additional participation from Bolt, Founder Collective, Project 11, and angel investors. The round brings the company’s total seed financing to more than $3.7 million.

The Mightier system, which parents can currently buy for $250, consists of a library of specially modified mobile phone games from acclaimed indie designers, three hours of coaching support, and a heart rate-monitoring wearable called the Mighty Band. It does not include a mobile device; Mightier expects users will have their own.

The Mighty Band monitors the child, but also affects the game.

“While you’re playing a game, eventually you’re going to come to a situation that’s hard for you and that’s going to push your heart rate up, or more formally it’s going to push your autonomic response up,” cofounder and Chief Scientific Officer Jason Kahn told MobiHealthNews. “Once that happens we do this counterintuitive thing of making the game harder. And that, for kids, is intentionally frustrating. So now they are in this space where the game has gotten harder and they have to find a way to back out to make the game easier again.”

The game offers up strategies for emotional regulation, like deep breathing, but it’s up to the child to calm themselves in order to beat the game.

Mightier is not currently seeking FDA clearance or looking to market the system as a therapeutic device. But that doesn’t mean the company hasn’t collected efficacy data.

In three separate randomized trials, families saw positive results from Mightier, including a 62 percent reduction in outbursts, a 40 percent reduction in oppositional behaviors, and a 19 percent reduction in parent stress. Some studies compared Mightier to a control group wearing exactly the same heart rate monitor and playing exactly the same game — the only difference was that the monitor didn’t communicate with the game.

“We’re very good at teaching kids skills,” Kahn said. “Lots of kids know about deep breathing, but they don’t always know how to apply them. So kids very quickly see ‘Here’s a setting where I can actually apply my skill and it makes the world easier. It makes it easier to interact with this.’ And they apply this skill under many different cognitive challenges and they just keep practicing and practicing. And that very simple loop, we call it a rep. It’s sort of like building that muscle memory of what to do when your brain starts to face a challenge.”

Mightier hopes the game will help teach emotional regulation to kids with a variety of neurological conditions, including ADHD, chronic anxiety, and autism, as well as kids with no diagnosis. And they hope to continue expanding their library of games from 15 to more than 25.

“The games are fun,” Kahn said. “They weren’t made by academics. They weren’t made by me. I feel like that’s a selling point.”