Homeostasis refers to the ability of organisms to maintain vital properties, such as body temperature, within a zone of viability, or of comfort, and the Gaia Hypothesis proposes that the Earth with its biota acts as a homeostatic whole. The Daisyworld model was proposed as one possible mechanism for providing this homeostatic regulation. Here a new and much simplified version of this model is presented, demonstrating that the combination of any ‘Hat function’ with any feedback, positive or negative, can lead to homeostasis through ‘Rein Control’. This principle is so general that it can be extended to other domains such as active perception, here demonstrated in a simulated robot.