When Ryan Green’s son Joel was 1 year old he was diagnosed with an aggressive brain cancer. Over the next few years, he underwent rounds of chemotherapy and radiation, only to have the cancer return.

Feeling helpless, Ryan turned to what he knew as a video game developer. He began working on a game as a way to understand and confront his son’s deteriorating health. He connected with the Kickstarter community, ultimately raising enough money to back the creation of the game, which made its debut Tuesday. It would have been Joel’s sixth birthday.

The result is That Dragon, Cancer, a deeply intimate, immersive video game that follows Joel’s fight with cancer over four years. But it’s not your typical slay-the-dragon type of game.

“You’re not trying to achieve a high score; you’re not shooting cancer cells with big bazookas, that’s not what this is about,” Ryan says in the Kickstarter trailer.

The game unfolds more like a diary, with the player catching glimpses of memories or snippets of disembodied voices. The player is left trying to make sense of the pieces.

In one scene, Joel floats happily down a playground slide, giggling, and in another he cries uncontrollably while the player navigates an empty hospital crib. Ryan’s tired voice urges, “It’s so late, Joel. Lay down … I can’t make you feel better.”

It’s heartbreaking, and as a player, it’s not always clear what to do to save Joel’s life, or even to help him sleep.

In 2014, the Green family relocated to San Francisco for experimental treatment, but it soon became apparent that it wouldn’t help. In March 2014, while the game was still being created, Joel passed away.

Ryan used recordings of Joel’s laughter and other audio collected during his son’s short life in the game. His wife, Amy Green, a writer and standup comedian, also contributed her voice and writing to the project. It’s part of a growing trend of video games that focus on narrative storytelling.

“We hope that players walk away with a sense of the grace that we experienced and also what it was like to be with Joel and to love him,” Amy says.

The Greens’ story also has been made into a documentary that will be released this year.

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