Head down to the lobby. Walk outside and travel two blocks northeast to the Washington State Convention Center, which is currently hosting PAX Prime, the country’s largest annual videogame expo. Enter the convention center and locate the escalator, just there, up the stairs to the left. Ascend to the fourth floor. Walk past the long lines of gamers waiting to take a spin through forthcoming big-budget releases like Tom Clancy’s The Division and Mad Max. Work your way back to the Indie Megabooth, a collection of more than 70 independently developed, artsier titles. There is a map; find the game you’re looking for, That Dragon, Cancer, tucked away in the northeast corner. As you reach the booth, notice the poster—a digital sketch of a large man in a hospital chair cradling a small boy, an IV delivering a toxic green fluid into the child’s body.

Green showed a demo of his game here in 2013, and you’ve heard the stories. Players breaking down in sobs and quickly exiting the booth. The emergency box of Kleenex, hastily procured and placed next to the monitors. The soothing reassurances to distraught gamers that Joel was, in fact, still alive.

Enter the booth. There are two monitors on a table. Players sit before them, silently steering through the latest demo. Here is what they see: a young boy, his facial features obscured, feeding bread crumbs to a duck, while his parents explain to his brothers why his treatment has left him unable to speak at age 2; a man sitting at a picnic table, ruminating on what his son must be experiencing without the words to express it; a playground, where the boy rocks on a toy horse, swings, giggles, spins on a carousel, then disappears; a path to a beach, where the boy is now strapped to a gurney, his tiny body hooked up to machines, the water filled with bobbing, gnarled tumors; the shadow of a dragon against the sea; a flight through the window of a hospital; a doctor telling the family that a recent MRI shows the boy’s tumors have returned; a nurse assuring them that the staff is very good at end-of-life care; the boy’s parents sitting still and silent while the room fills with water; the boy, now sitting in a rowboat, wearing a tiny life jacket that doesn’t look sufficient to protect him.

You know you will have to play this game at some point. You will have to confront all of these moments, and many more. But not yet. Instead, you find the bespectacled man wearing a narrow-brimmed straw fedora and a close-cut red beard. This is Ryan Green. Hold out your hand and share a sad smile, a silent acknowledgment of what you both know—what Green himself didn’t know when he started working on That Dragon, Cancer, what he didn’t know the first time he brought it here to PAX. You know how the game ends. You know that Joel dies.

They wait somberly in line: cosplayers, young women, middle-aged men. They sit in front of the monitor, put on the Bose noise-canceling headphones, and pick up the Xbox controller. Fifteen minutes later they stand and push back from the table. Many of them affect sheepish grins, rise quietly, walk off abruptly without making eye contact. A few get misty-eyed, clearly shaken, collecting themselves before they leave. And then there’s the developer who starts weeping and says, “I don’t want to be here at PAX; I want to be home with my kids.” The couple whose own daughter survived cancer and who have followed the game’s development for years. The boy who staggers away from the screen as if emerging from a particularly punishing roller coaster.

“Are you OK?” Green asks.

“It’s just so sad,” the boy says in a hushed tone, staring off. He wanders away, dazed. A few minutes later he returns to collect the backpack he has inadvertently left behind.

Green, on the other hand, doesn’t at this moment appear particularly haunted or upset. He stands in front of his booth with the studied casualness of someone who knows that people nearby are talking about him. His burly figure would be imposing if he weren’t dressed in cargo shorts and flip-flops, a wardrobe that—along with his sunny, authoritative demeanor—gives him the air of a summer camp director. Despite the circumstances, he is happy to be here.

An experienced programmer, Green is relatively new to the indie-game world. Until recently, he worked full-time designing software for a Denver-based dialysis company, a job he held for 11 years. In 2008, just before Joel was born, Green, who had long dabbled in filmmaking, poetry, and art, decided to try his hand at game-making. He spent his evenings and weekends learning how to use the Torque game engine and cranking out silly iPhone trifles with names like Sir Roly Poly and Little Piñata. They didn’t sell well, but Green enjoyed making them. He had always fantasized about pursuing a creative career, and he and Amy hatched a plan to save up enough money for him to quit his job after a few years and build games full-time.

That Dragon, Cancer explores spiritual and existential quandaries that have haunted humanity since Job.

When the Greens received Joel’s first cancer diagnosis in January 2010, that creative outlet became more important to Ryan, even as it grew more difficult for him to pursue. The Greens live in Loveland, Colorado, about an hour from Joel’s oncologists in Denver, and Ryan found his schedule overtaken by late-night trips to the emergency room and overnight stays in the ICU, wrestling with feeding tubes and chemotherapy pills, juggling childcare for the Greens’ other children, and all the other logistical, emotional, and psychological challenges that come with tending to a seriously sick child. Ryan’s boss told him to take as much time as he needed, and he ratcheted back to working about 30 hours a week. At the same time, he found himself taking on contract game-design work, something to keep him creatively engaged during those long and terrifying months.

Then, just under a year later, Joel was declared terminal. The news caused Green to reassess his life. The dialysis company was giving him paid time off and the flexibility to take care of his family, and he was using it to work for somebody else. He was one month away from a $30,000 retention bonus—money that was crucial to his plan to strike out on his own—but he couldn’t stomach the idea of accepting it under such pretenses. Over the protests of his employer, he quit.

“Everybody around me was like, ‘Don’t fall on your sword, you don’t have to do this,’” Green says. “I don’t want it to sound more noble than it was, but it just felt like a moment where I could have some integrity.”

“You think, ‘Ugh, I kind of hate this, but I get it,’” Amy says. “Both of us at that point were like, ‘Let’s do what you’re passionate about and not just get through life. Let’s make decisions we love.’”

For Green, that meant making games that explored religious themes. He started doing full-time contract work for Soma Games, a Newberg, Oregon-based developer of Christian videogames. In late 2010 he met Larson, an indie-game veteran from Des Moines, Iowa. Larson, another devoted Christian, had been spending time on a “not-games” forum, an online discussion for developers interested in avoiding all the usual gamelike trappings—the puzzles and quests and levels—to discover what else the medium might be capable of. I Wish I Were the Moon was a clickable tone poem about lost love. Proteus had players wander around an interactive landscape. Larson says his interest in not-games was purely intellectual, not spiritual, but the effort to move beyond performance-based reward systems seems to track with some of his deeply held philosophical beliefs. “The idea of grace is that you don’t have to do something good to earn your salvation,” he says. “People are always so concerned about what you do in a game, and they can be that way about life too. Whereas some people, depending on what kind of faith they have or what kind of person they are, that’s not necessarily what defines them.”

The Greens—Ryan, Amy, and their four children—live in a small townhouse about halfway between Loveland’s big-box commercial district and its sleepy, red-brick downtown. Their home and schedule reflect a laissez-faire approach to time and space management. The shelves and walls are cluttered with family photos, paintings, figurines of a man and woman cradling a baby. A stack of board games towers atop the refrigerator. Two beat-up Xbox consoles inhabit the entertainment center.

On a sun-blasted September afternoon, I pull up a chair in front of their TV. Green takes a seat next to me. Larson, who has flown in to work on the game for a few days, settles into an easy chair. Amy is here too, sitting next to Jon Hillman, a local composer who signed on as the game’s sound designer after meeting Green at a coffee shop. The game’s two other far-flung designers, Ryan Cousins and Brock Henderson, are waiting to discuss my experience via Google Hangouts. Green smiles and hands me an Xbox controller. I am about to become the first person outside the core development team to play a full run-through of That Dragon, Cancer.

I am not a great player of videogames. I get disoriented easily, I am quickly overwhelmed by complicated button combinations, and I often pass right over the clues and prompts that designers use to nudge players through the story.

But That Dragon, Cancer is not a tricky game to master. Indeed, it’s barely a game at all, more a collection of scenarios that the player explores and clicks through. There is some degree of agency—you can decide how long to spend in any particular scene, for instance—but the overwhelming sensation is one of being a bug caught in a rushing river; you might veer a few degrees in either direction, but you can’t alter the overall flow.

All videogames are deterministic; some just mask it better than others. The Super Mario Bros. series may give the appearance of serendipity, but creator Shigeru Miyamoto planned every surprise down to the pixel, a kind of 8-bit Truman Show of false autonomy. For all their free-range chaos, the massively multiplayer games of the ’90s and ’00s were ruled by “gods” and “immortals”—admins who could spy on players, take control of their avatars, or single-handedly wipe objects out of existence. Today, many of the most popular cinematic titles hew to what Koster calls the “string of pearls” design: lots of freedom within individual levels, but a rigid structure that ultimately forces the player’s hand. “You have all the choices in the world, until you have to move on and do what they tell you,” he says.

By turning his personal loss into art, Green has also been able to convert his grief into labor. At times, that’s a gift—when he’s designing a landscape or animating a character’s movement, he can almost lose sight of the larger story. But occasionally he’ll be crippled by the enormity of what he’s grappling with. Once, he says, he broke down sobbing while positioning images of himself and Joel on a hospital bed. Cousins, the designer, told me that he sometimes hesitated before sending Green new animations of his son, for fear it might be overwhelming. Larson sometimes has to take extended breaks, particularly when he’s doing speed-runs—high-velocity run-throughs of the entire game—experiencing Joel’s decline over and over again.

In a way, the process of working on the game in the months since Joel’s death has given Green the opportunity to spend more time with his son—or at least a digital approximation of him, what Green calls an “echo” of who Joel used to be. “If I look at the game objectively,” Amy says, “of course it’s all just to make his life matter. You wanted his life to matter so much, and he died young, and in a lot of ways his life will only matter if we make it matter. When the project is done, that process ends. And then we get to see, does this matter?”

Toward the end of the run-through, I enter a giant cathedral. This is the scene that Green has worked on most diligently since Joel’s death. It replaces the lever-pulling scene, his initial idea to urge the player toward accepting his own powerlessness. This is the scene, Green says, that embodies all the wrestling with God he has endured since his son’s death, the scene that once provided answers but now leaves only questions. I brace myself.

“This isn’t quite done yet,” Green says. “I’d better walk you through it.”

I exhale and sit back as he takes the controller. A wave washes over me. It feels like relief. It’s no longer my job to navigate this treacherous emotional landscape. All I have to do now is put myself in the designer’s hands.