Joel Green was diagnosed with terminal brain cancer in 2010 when he was just one year old. The tumors left him partially blind and unable to speak. But at first the treatment was working. Ryan Green, a video game developer, and his wife, Amy, decided to tell their story in an unlikely way: through a video game. That Dragon, Cancer is an impressionistic game that chronicles Joel's battle with cancer and the emotional ups and downs of caring for him. Ben Tracy reports.