You slump down in the chair, defeated. And you pray.

“Oh God, I want him here with me,” you say. “Please.”

The crying stops. Joel is asleep, at peace – for the moment. The screen fades to black.

This is a scene from Ryan Green’s intimate and innovative new video game That Dragon, Cancer – a gut-wrenching exploration of what it’s like for a family to lose their young son to a terminal illness – which was released on Tuesday.

But it’s also a scene from Green’s own life. It’s the experience that, four years ago, formed the kernel of the idea that would become That Dragon, Cancer. Not because of how much it resembled a classic video game – all vanquishing enemies and navigating perils – but because of how much it didn’t.

“At first (Joel’s diagnosis) was an adventure and I could be this caring father ... this hero who was going to help fight the disease,” says Green. “But there are parts of our lives where there’s just nothing we can do. We don’t know the answers. And that’s where we receive help.”

The scene in the hospital room was the one time in his life that Green – a devout Christian – had prayed and felt like he’d got a direct reply.

“It was a moment of grace,” he says, simply. “And I wanted to share it with people.”

Joel Green was diagnosed with an aggressive brain tumour in 2010, not long after his first birthday. He died on March 13, 2014, at age five.

In between were the four most harrowing years that his parents, Amy and Ryan Green, had ever experienced. Turning those years into a video game was a way of preserving their memories of their beloved son, the profound and painful moments as well as all the mundane miracles of a small child’s life. It was a way of honouring Joel, of marking his presence in a world he barely got to see himself. And it was a way to give some narrative order to cancer’s chaos, to turn the story of a failed fight to slay a dragon into a message about grace.

Over the course of 14 five-to-10-minute episodes, players are introduced to Joel and guided through stages of his life and death from cancer. The animation is vivid, but abstract. The character’s voices come from home videos, or taped sessions in a studio. Baby Joel’s infectious giggle comes from recordings of Joel himself.

In one chapter, the player pushes Joel down the slide at a playground while the little boy laughs and laughs. In another, you watch as Amy and Ryan are shown an MRI of their son’s tumour, listen as they’re told that the prognosis is not good.

Sometimes there’s something for the player to do – navigate a go-cart around a hospital hallway; direct a tiny Joel, dangling from balloons made of blown-up surgical gloves, as he wends through prickly projectiles representing his cancer.

The game most resembles a traditional video game during the chapter in which Ryan and Amy explain Joel’s illness to their other kids. It’s called, “Joel the baby knight.” Using the arrow keys, the player evades flaming fire balls and slays vicious beasts while journeying to slay the dragon called cancer.

But mostly there’s a lot of watching and experiencing, letting emotion wash over you as you witness a family confront a child’s death, waiting for a moment of grace.

Green and co-developer Josh Larson started working on the game a year and a half before Joel passed away. They’d met online and bonded over a shared interest in non-traditional, spiritual games, ones less oriented toward risk and reward and more focused on cultivating empathy. The duo had built a few short projects together, but they were saving up for something bigger.

In November 2012, the tearful scene in the hospital almost two years old but still fresh in Green’s mind, he suggested to his partner: “Why not Joel?”

They started with a demo of that hospital scene: Green fruitlessly seeking to soothe the crying Joel, growing more and more desperate as the baby’s wails grow louder and louder. They brought it to a bunch of video game conferences, not expecting much but hoping to find a financial backer or two.

The response was instantaneous and enormous.

“We will all meet this thing, or have already met it,” wrote game writer Jenn Frank after playing the demo at a 2013 conference in San Francisco. “Maybe that should be scary, but That Dragon, Cancer is about sustaining the hope and joy of life for just as long as we can.”

Larson and the Greens got their funding, and That Dragon, Cancer became a cause celebre in the indie gaming world. It was the focus of a documentary, Thank You for Playing. It was written up on gaming sites and in the New York Times.

Meanwhile, Joel was not getting better. He would experience 15 tumours and nine rounds of radiation before ultimately succumbing to cancer two months after he turned five.

After Joel died there was no question that Green and Larson would keep going with their project. But they scrapped half their storyboard and changed the game’s focus. It would be less linear, less about narrative, less centred around moving through levels of play. And it would be more about Joel: being with him, watching him laugh, getting to experience what he loved.

“It was kind of this overwhelming desire to want to spend time with him again,” Green says.

During the excruciating months that followed, That Dragon, Cancer offered some sense of purpose and continuity amid the ache of Joel’s absence. It was the one thing in the Greens’ life that didn’t change with his death.

But now, even that source of solace has come to an end. Nearly two years after Joel’s death, on the day he would have turned seven, the Greens are celebrating with the release of their game and a birthday party of sorts. They’re asking friends and fans to share their experiences of the game, as well as their own stories of love and loss.

For Green, who has been pulling 80- to 90-hour weeks for the past few months to get the game ready for launch, there hasn’t been much time to contemplate what life will be like after That Dragon, Cancer – that last little piece of his son – has been released.

But when he does pause, he feels fear, he admits. Fear that finishing the game will be like losing Joel all over again.

“I’ve spent so much time mourning Joel,” he says. “Remembering him, honouring him, and building things for him. And the deep grieving – I almost wonder if I’ve put that off a bit. I’m ready to be done. But it’s also scary because I think I might grieve in a new way.”

Nevertheless, Green is eager for this deeply personal project to become public, to hear from people who have played the game and connected with it in some way. Already, he’s received countless messages from strangers who were touched by his story. Razer Inc, the company that helped develop That Dragon, Cancer, announced it would be donating much of the proceeds from its sales of the game to Morgan Adams Foundation and Family House SF, two cancer non-profits that helped the Greens during Joel’s illness. The company also was hosting a pancake breakfast for all 600 of its employees, Green says.

“I hope that people allow the game to change them,” he says. “Us inviting you as a friend into what we’ve gone through, it will allow you to share in our pain, but also share in our comfort. ... I think that can take us really far. It can change how we treat each other, change how we talk about each other. Joel’s story can have such rippling effects, if we start with our hearts.”

He pauses, then laughs.

“Everybody wants their child to change the world,” he continues. “I have unreasonably high hopes, just like any proud father would.”

The Washington Post