Cats hunt dogs and sometimes eat them. The kindness index regulates the probability of being eaten by a cat. Cats can die when they collide with stones. The number of possible collisions before the fatal outcome is determined randomly. When faced with flowers, cats increase their level of kindness, and dogs increase their energy. Cats also have an energy indicator, when eating dogs, they appropriate the energy of the victim to themselves. All animals have an age parameter. If the energy runs out or the age reaches one hundred, the animals die.