Homeostasis is all about trying to keep Bill, a guy that does stupid things, alive. Mr. Bill is constantly doing stuff that is throwing his system out of whack. You will play the role of his hormones in trying to get things closer to where they should be. Bill wont make this easy. Many of the hormones work together and some are even required for others to work.
At the start of each round a Bill card is flipped. Bill has done something and his homeostatic variables of pH, blood glucose, and blood pressure have changed as a result. Players have hormone cards that impact those same variables. They choose which ones to play to make Bill's situation less dire. At least until Bill does something else. Your goal is to get through all of the Mr. Bill cards and keep him alive.