That Dragon, Cancer is an autobiographical and crowd-funded game created with a small team and based on the experience of the couple Ryan Green and Amy Green, who lost their son Joel Evan Green to cancer. The game consists of fourteen interactive sequences that chronicle their time with Joel, incorporating their thoughts and experiences, and voiced by themselves and their other children. It represents a love letter to their son and a way to immortalize him. Joel was diagnosed with an atypical teratoid rhabdoid tumor when he was twelve months old, leading to terminal cancer, but he went on to live for four more years until he passed away in 2014.
Each scene shows a different moment of their time together with Joel, both the highs and the lows. Scenes are often abstract or involve metaphorical interpretations of situations and are played from a first-person or a third-person perspective with small amounts of interaction and exploration. Sometimes there are choices for the player or optional parts that can be explored or examined. There are scenes at the pond, playing with a duck, in the playground, the hospital and so on. Scenes show both the positive moments such as Joel playing or the conversations with the other children, but also the couple when they argue, the moment of the first diagnosis, the conflict between science and faith and so on. A part of the crowd-funded contributions also involves messages and art incorporated in the game.
Along with the game, a documentary called Thank You for Playing was filmed, documenting the game's development and the last years of Joel's life. It was released in 2016. The game was released on what would have been Joel's seventh birthday.