In a Prius you press down the brake and your engine siphons off kinetic energy, which it uses to help power the car. It’s called regenerative braking, an ingenious method for taking something that was once unproductive (braking) and making it productive.

One intriguing application for this strategy of taking something unproductive and making it productive is in games. I don’t mean anything as tacky as redeeming points for prizes. Imagine instead that while a person played he was also contributing something tangible and important. That is, a byproduct of playing is a contribution to society.

I’m talking about games that my favorite pie-in-the-sky research and development agency, has just released.

With Verigames  DARPA (Defense Advanced Research Projects Agency) is offering five free puzzle games that also help detect flaws in computer programming, which is an intensely laborious process, especially with some software composed of millions of lines of code. First software is scanned using automated programs that flag small snippets of code that look to have flaws that could lead to privilege escalation or buffer overflows. These errant sections are translated into mathematical formulae, which are then woven into the fabric of the game. When a player solves a puzzle he is also improving the code.

For example, in the game Xylem, a player visits a tropical island and catalogues never-before-seen plants — which are really just representations of code — by composing short descriptions. Flow Jam has a player tinker with a cable network to maximize throughput while in CircuitBot, a player controls a team of robots to carry out a mission to asteroids, planets and moons. As the promotional copy on DARPA’s Verigames website puts it:

“You’ll build factories that harvest and refine resources and generate goods. Eventually your robots will build facilities for human habitations at distant locations. You’ll manage the resources for each mission and choose when to sell, buy or ship resources to and from Earth.”

DARPA’s ultimate goal is to create “fun and engaging games that represent the underlying mathematical concepts,” so that “we empower the non-experts to effectively do the work of the formal verification experts — simply by playing and completing the game objectives.”

This is not new. A growing number of crowd sourced games are attacking various challenges. In SETI@home (for Search for Extra-Terrestrial Intelligence) users scan the galaxy for extraterrestrial life. In Galaxy Zoo, conceived to aid astronomers in classifying “deep sky objects” — planets, solar systems, and the like — designers estimated it would take a year for players to classify one million galaxy images. After its first day, players classified some 70,000 objects an hour, and in the first year 150,000 players amassed fifty times that, contributing 50 million classifications. With foldit, players manipulate animated proteins on their screens. As a result, a self-described “lowly lab technician” and her team discovered in 10 days the key to a protein-cutting enzyme from an AIDS-like virus in rhesus monkeys, a problem that eluded scientists for more than a decade.

Down here on earth, WhaleFM, through its Whale Song Project, has rounded up legions of citizen oceanographers to listen to orcas and assist researchers in matching similar-sounding calls. Out of MIT comes EyeWire, which looks to an online community to map connections in the retina to help neuroscientists learn more about how it assists visual perception. Another game from DARPA was a contest to piece together documents that had been shredded into 10,000 pieces, which the winning team solved by customizing algorithms to suggest puzzle pairings and then having humans put them back together.

Games designers aren’t the only ones to recognize the importance of efficiency. When Intel released the Atom chip in 2008, it was a major departure for a company that until then had been engaged in one-upmanship with its rivals over who could produce faster, more powerful chips. None of these chipmakers paid attention to battery drain or heat, both natural side effects of all this revved up processing power. For the first time Intel released a new chip that was not faster than previous processors, nor did it do more. In fact, it did less. But it needed a fraction of the battery power (10 times less, according to Intel) and therein gave rise to a revolution in mobile technology.

Lately, I’ve become obsessed with this idea that every time we do something, we should be able to either accomplish or create something else as a byproduct of doing that something. Like with these games: play and you are also contributing something.

Let’s take it a few steps further. Wouldn’t it be great if we could walk down a sidewalk and our every heel-ball-toe landing created energy that could be used to power portions of the city? What if we could do that for all the cars, buses and trucks that navigate thousands of miles of asphalt in the New York area? Closer to home maybe we could power portable devices with our body motion. While we’re at it how about linking up exercise bikes in gyms to butter churns?

Until this day arrives, though, we can play games and while we’re at it clean up some computer code. Now that’s a win-win.