Chemistry

There are two sources of energy in the dish: food and the atmosphere. By breathing the elements in the atmosphere, a narjillo can survive and reproduce successfully even without ever consuming food.

The atmosphere contains four chemical elements: Oxygen, Hydrogen, Nitrogen and "Element X", also known as the Catalyst. The rules of breathing are complicated, but the result is simple. First, here are the rules:

• Each Narjillo can breath one of the first three elements, depending on its dominant color: for example, a narjillo that is mostly red can breathe Oxygen, while a narjillo that is mostly green can breath Hydrogen.
• As it breathes, the narjillo converts that element to another element, that is determined by its genes. For example, it can convert Oxygen to Nitrogen. A Narjillo can never convert an element into itself (narjillos that are unlucky enough to be born with a set of genes that convert, for example, Oxygen to Oxygen, just cannot breathe).
• As it breathes, the narjillo also gains energy. The amount of energy it gains depends on the density of its breathed element in the atmosphere. For example, if the atmosphere is mostly Nitrogen, then a narjillo that breathes nitrogen can live and prosper on breathing alone, even without ever eating food. On the other hand, if the atmosphere is mostly Oxygen and Hydrogen, then a narjillo that breathes Nitrogen gains little or no energy from breathing.
• The Catalyst has a special role: all narjillos need the Catalyst to breathe, but there is a fixed amount of Catalyst in the atmosphere, that is continuously refilled. This fixed amount is divided across all narjillos in the dish at every tick. This means that if there are just a few narjillos, they will get a lot of catalyst, and they will breathe very efficiently. As the number of narjillos rises, the amount of catalyst available for each individual drops, and all creatures become less efficient at breathing.

Complicated rules, as I told you-but the outcome is simple: Narjillos help each other breathe in a closed-cycle ecosystem. It works like this: imagine that a species of narjillos evolves, that converts Oxygen to Nitrogen. This species will quickly exhaust all the Oxygen in the atmosphere, and become unable to breathe. On the other hand, if the dish contains a second species that converts Nitrogen to Oxygen, then the two species can reach a stable equilibrium, where they both can prosper. Each species will consume its own favourite element, and convert it to the element that the other species needs to survive. On the other hand, since the Catalyst is a fixed, limited resource, the two species cannot reproduce indefinitely: too many individuals would consume all the available Catalyst, and become unable to breathe. The result is a balanced ecosystem where no species can easily take over the dish, or overpopulate it, without ultimately causing its own extinction.

Breathing is not strictly necessary. A narjillo could survive and reproduce successfully without breathing, as long as it gets a lot of energy from food. But reaching food requires movement, that consumes energy. So a narjillo has to evolve its own way of gaining energy, which usually involves either moving a lot to reach food, or standing very still to spare energy, and get energy from the atmosphere-or any combination of the two.