The five-year-old boy whose terminal illness was the basis for the forthcoming game That Dragon, Cancer has died. Joel Green passed away early this morning, his father said.

That Dragon, Cancer, due to launch later this year on Ouya, is an adventure game meant to tell the story of two parents, Ryan and Amy Green, raising a son battling cancer nearly since his birth. Green is developing the title with Josh Larson, a friend.

The Greens shared the above image this afternoon on the development blog for That Dragon, Cancer.

Last night, in an update on a site created to document Joel's treatment, his mother wrote that he had been taken to Children's Hospital in San Francisco and was receiving palliative treatment, with the expectation that he had a week to live.

"We know that nothing we give Joel now can bring to us the life he had, but that God can, with a word, give Joel a life he has never yet experienced," Amy Green wrote. "Right now, things can not go back to being OK anymore, but there is a possibility still, nearer than it has ever been, that things can be unbelievably amazing."

In a demo shown at the Game Developers Conference last spring, players inhabited the persona of Ryan Green, in the intensive care unit of a hospital watching his son laying in a bed after a round of treatment.

Green himself chose that sequence to show at GDC because it was so difficult for a viewer to cope with, emotionally. "That was one of the darkest moments of my experience in this whole thing with cancer," Green told Polygon.

"I've re-created that experience, to show people what I went through—to give them a glimpse into what gave us rest in the end."