“Everyone complains about kids not having enough free time, and being addicted to technology,” Mike says. “There are a million studies documenting the negative effects of lack of free play in children. Well, we know the harms. I asked myself: What am I going to do about it for my kids?”

He analyzed the problem like an entrepreneur, by thinking of children as consumers and seeing their time as a scarce resource. Playing outside has to compete with screen time. (A typical 2-to-10-year-old child spends at least a couple of hours a day on screens; tweens spend more than four.) Parents who limit screen time, as local families often do, tend to compensate by piling on extracurricular activities and tutors.

Even if a boy wanted to play outside, Mike explains, with whom would he play? At any given hour, there might be a 30 percent chance that some kid was playing outside. But the so-called network effect, in which children influence one another’s behavior, means that 30 percent might as well be zero, because it is low enough that no boy can count on it and so will default to his screen — causing the percentage to drop lower. That is, kids don’t play outside because other kids don’t play outside. Playing outside becomes like Betamax — it’s just obsolete. But in the case of a playborhood, the vicious circle transforms into a virtuous one: When there’s always another kid to play with, most kids want to play.

As part of Mike’s quest for a playborhood, he began doing research and visiting neighborhoods in different parts of the country that he thought might fit his vision. The first place he visited was N Street in Davis, Calif., a cluster of around 20 houses that share land and hold regular dinners together. Children wander around freely, crossing backyards and playing in the collective spaces: Ping-Pong table, pizza oven and community garden. Mike told me the story of Lucy, a toddler adopted from China by a single mom who lived on N Street. When Lucy was 3, her mother died of cancer. But before she died, her mother gave every house a refrigerator magnet with a picture of Lucy on it. While the founders of N Street formally adopted Lucy, the entire community supported her. Mike pointed out that the childhood Lucy was having on N Street may be akin to one she might have enjoyed in a village in rural China, but it was extraordinary in suburban America. Lucy could wander around fearlessly, knowing she had 19 other houses where she could walk right in and expect a snack.

Mike spent some time in the Lyman Place neighborhood in the Bronx, where grandmothers and other residents organized to watch the streets — so dangerous that children were afraid to play outside — and block them off in the summer to create a neighborhood camp, staffed by local teenagers and volunteers. Mike also found his way to Share-It Square in Southeast Portland, Ore., a random intersection that became a community when a local architect mobilized neighbors to convert a condemned house on one corner into a “Kids’ Klubhouse”: a funky open-air structure that features a couch, a message board, a book-exchange box, a solar-powered tea station and toys.

Mike was aware of limits to the analogies. Those playborhoods were in lower- and middle-class communities; he and Perla had settled on a house in the Allied Arts area of Menlo Park, where the median home price is $2 million. (And the houses in neighboring North Palo Alto and Atherton cost even more.) Mike found himself up against the fact that in America, the ethos of wealth and the ethos of community are often in conflict: Part of what the wealthy feel they are buying is privacy and the ability to be choosy about whom they socialize with. Mike was determined that his kids would not only know their neighbors but would also see them, every day.

In order to achieve this, Mike decided he had to corral his neighbors to sign on to his platform. He designed big neon-yellow plastic signs like those used to warn of wet floors, emblazoned with an icon of children playing and the word Playborhood. He invited kids to parties and gave the signs to their parents, to put in their yards and on the road in front of their houses so their children could “reclaim the streets from cars.” (We had the sign in our driveway, but my husband accidentally ran over it, and the shards of yellow plastic remained there for months — a good reminder, he said, of what happens to children who play in the street.)