Kellee Santiago’s voice hits a particularly enthusiastic high pitch as she recalls a conversation with an astronaut that inspired Journey, the latest offering from offbeat video-game producer thatgamecompany. “We are pretty powerful in our daily lives, we can drive pretty fast, we can fly, we can access anyone at any time,” trills the California-based independent company’s co-founder and evangelical president.

“But when you land on the moon and you see all of the things you care about, just the size of your thumb; it is a moment of real awe and wonder that we don’t really get to have. Maybe it is a fundamental aspect of our human experience that we are lacking because of all the power in our lives?” She lets the big existential question linger dramatically before adding: “Certainly when we look at video games it is completely non-existent!”

It is exactly this brand of wide eyed wonderment that has been thatgamecompany’s calling card since it was created in 2006 by Santiago and virtuoso game designer Jenova Chen at the University of Southern California’s School of Cinematic Arts.

By embracing a development process that shuns rigid developmental mechanics and balls-out commercialism to focus on pure emotional response, their company has consistently upended gaming preconceptions through a three-title deal to produce downloadable games for Sony’s PlayStation 3 PlayStation Network Service.

The output of thatgamecompany is described as “core games” that appeal not only to hardcore gamers, but also dormant and even non-gamers by delivering immersive, albeit fleeting experiences that pack a weighty emotional punch.

First, there was Fl0w, based on Chen’s research into dynamic difficulty adjustment and the theoretical concept of mental immersion, which sees the player assume the role of an ever-evolving micro-organism. Then there was Flower, wherein players employ the PlayStation 3’s motion-sensitive controller to direct a gust of wind blowing a flower petal through the air, accumulating further petals along the way and causing subtle changes in the surrounding environment.

The games forged an entirely new genre of emotive gameplay, becoming huge, award-winning successes and prompting critics to gush that boundaries between video games and art were being blurred. Within 10 days Fl0w had racked up 300,000 downloads on its way to becoming the biggest PlayStation Network hit of 2007, while Flower was among the top 10 in 2009. Both made good money (though Santiago won’t reveal how much) and Sony was vindicated and widely praised for investing in the left field.

“We had no idea how our games would be received,” says Santiago, whose personal journey into the gaming industry came via a formative period combining experimental theatre with digital media in New York.

“But I believed that it was totally possible to make these kind of games, and that there were many, many more people like myself who wanted these kind of interactive experiences.”

Sony clearly agrees, recently announcing it was pumping $20m (€15m)into PlayStation Network exclusives, many of which will hail from the creative talent of staunch independents. Some analysts have pointed out that the move is likely to be at least partly influenced by the soaraway success of Flower.

Due for release next spring, Journey is thatgamecompany’s first online title and comes across as a quantum leap forward in terms of scope, as well as a logical continuation of every project that has come before.

The concept is typically abstruse: the player controls a robed figure who wakes up in the desert and must inexplicably embark on a journey towards a mountain. On the way, they will encounter other online players who they can collaborate with should they wish to, though there are no words, voices or PlayStation Network IDs to clutter the experience. Players can also go it alone if they choose, but this will make them appear more disconnected and less approachable to others.

Santiago admits that Journey is, more so than most thatgamecompany titles, a shot in the dark and that she had no idea how people would respond to being shorn of all the usual gaming bells and whistles.

“The first challenge we set out to tackle was, could you make an online experience unlike any other in existence,” she says. “If you are experiencing this virtual space with another person and you have no idea where they are from, how old they are, their gender – what does that mean?”

A recent beta test with thousands of participants assuaged any fears she may have had, while a febrile online buzz has fired expectations.

Journey is thatgamecompany’s last obligation to Sony; the current focus is on delivering it with maximum impact. But while the company’s track record and fanbase means that new deals will not be hard to come by, the notion of large-scale commercial paydirt is firmly off the agenda.

The 12-strong enterprise certainly has the wherewithal to mount an assault on the mainstream; several action-centred games created “for fun” have piqued Sony’s interest, yet Santiago and Chen say they are averse to compromising the integrity and iterative developmental space they thrive in.

Santiago is also supporting other independent developers as one of the key figures behind the Indie Fund, a novel funding mechanism for companies that want to evolve unencumbered by big budget shackles in an industry that was last year estimated at $105bn worldwide by a gaming-sector expert at independent banking firm Avista Partners.

“There is so much uncovered territory in video games,” Santiago explains. “I always joke that we are the only studio that hopes people copy us, because we don’t want our games to be niche products. One day action titles and military shooters won’t be the predominant genres on the shelves or online. Until that point I feel like I need to be a part of continuing to push the boundaries.”