Ryan and Amy Green were facing the unfaceable: their youngest son, Joel was diagnosed with terminal cancer after his first birthday. Producer Sruthi Pinnamaneni tells the story of how Ryan and Amy stumble onto an unlikely way of processing their experience fighting alongside Joel: they decide to turn it into a video game. In the end, they find themselves facing what might be, for a game designer or a parent, the hardest design problem ever.

Correction: In the original audio we stated that the survival rate of childhood AT/RT cancer is 50% over five years. But studies suggest the survival rate is 50% over two years. The audio has been updated to reflect this change.

For an extended version of this story and a bunch more incredible stories, go check out Reply All.

Special thanks to Eilis O’ Neill, Jon Hillman, and Josh Larson. This episode included audio from “Thank You For Playing,” a documentary film about the creation of That Dragon, Cancer by David Osit & Malika Zouhali-Worrall. You can learn more about the film and where you can see it, at thankyouforplayingfilm.com. For more, we suggest reading Wired's "Playing For Time."