I just listened to a Podcast about this! It sounded like the most depressing thing I had ever heard. It was mostly a coping mechanism for the parents.

That Dragon, Cancer is a video game developed by Ryan and Amy Green, Josh Larson, and a small team under the name Numinous Games. The game is based on the Greens' experience of raising their son Joel, who was diagnosed with terminal cancer at twelve months old, and though only given a short time to live, continued to survive for four more years before eventually succumbing to the cancer in March 2014. The game is designed to have the player experience the low and high moments of this period in the style of a point-and-click adventure game, using the medium's interactivity and immersion to relate the tale in ways that a film cannot. The game initially was developed to relate Ryan and Amy's personal experience with Joel when they were uncertain of his health, but following his death, they reworked much of the game to memorialize and personalize their time and interactions with Joel for the player. Alongside the game, a documentary Thank You for Playing, documenting both the last few years of Joel's life and the development of the game, has been filmed to be aired in 2016.
@previous (C)
That was incredibly helpful. Thank you for posting.
@OP
Someone will probably mod it.
@previous (Big Daddy Derek !Uvm54ORbmo)
hope they add first person shooter game modes