How it works
A middle-depth look at the rules that actually run, and a clear line between what is explicitly implemented and what may or may not emerge from it.
Organisms
Each organism is a small, distinct entity with a position, an energy level, a health value, an age and a lineage. It carries a compact neural network that maps what it can sense to what it does next.
Sensing
Organisms perceive a limited, local slice of the world: nearby terrain, nearby objects, nearby other organisms, and a few internal signals such as their own energy. They do not have global knowledge of the map or of other organisms elsewhere in it.
Neural controllers
Each organism's decisions come from a small neural network, not a hand-written behaviour tree. The network's connection weights are the product of evolution: they are inherited, mutated across generations, and occasionally adjusted within an individual's own lifetime as it encounters consequences of its own actions (lifetime plasticity, covered further in the science page).
Movement, energy and eating
Moving, acting and simply staying alive cost energy. Organisms recover energy by eating: consuming plant matter or other available food sources in the world. An organism that cannot find enough energy weakens and, eventually, dies.
Reproduction and mutation
Organisms with sufficient energy can reproduce, passing a mutated copy of their neural network to offspring. Mutation is small and random. Selection is not: whichever variants happen to survive and reproduce more successfully become more common over time.
Lifetime plasticity
Beyond inherited, generational change, an individual organism's own controller can adjust somewhat during its lifetime in response to what happens to it. This is a real, implemented mechanism, distinct from evolutionary change across generations, and it is documented separately in the science page.
Materials and the environment
The world contains material: plant matter, wood, stone and other objects that organisms can pick up, carry, drop or otherwise manipulate. Manipulating material changes the world's physical state, and that change can persist long after the organism that caused it has died.
Manipulation and environmental modification
Organisms can move objects, and doing so can alter which cells are easy or hard to pass through. Repeated modification in one place leaves a lasting mark on the terrain. This creates the physical possibility for more complex environmental strategies to matter, though whether any given population actually exploits that possibility is a separate, empirical question (see research notes).
Weather, day and night, and fire
The world has a real diurnal cycle driving ambient temperature, and a day/night presentation that follows it. Fire can start and spread under the right conditions and interacts with material and organisms in the world. These are authoritative physical processes, not decoration.
Persistent traces
Ground clutter, charred material, remains and altered terrain do not automatically clean themselves up. What has happened in a place tends to still be legible there afterwards.
Lineages
Every organism's ancestry is tracked back to its founders. This makes it possible to say, honestly, which populations a given organism descends from, when a lineage diverged, and when one goes extinct.
What is implemented, and what is not claimed
Everything above is an explicitly implemented rule. Higher-level behaviours you might read about elsewhere on this site, such as whether organisms coordinate, avoid danger cleverly, or exploit the environment in sophisticated ways, are not rules. They are, at most, patterns that may or may not appear as a consequence of the rules above interacting over time. See claim discipline for how this site distinguishes the two.