Game Development Reference
In-Depth Information
CONWAY'S GAME OF
LIFE
John Conway, a mathematician, created
Life
, an early, simple A-life game.
Life
depicts
cellular automata
, simulated beings that live on a two-dimensional grid. All these autom-
ata do is survive, reproduce, and die in a series of generations, according to three very
simple rules:
•
Death: If a cell has 0 or 1 neighbor cells, it dies of loneliness. If it has 4 or more neigh-
bors, it dies of overcrowding.
•
Survival: If a cell has exactly 2 or 3 neighbor cells, it survives to the next generation.
•
Birth: If an empty spot on the grid has exactly 3 neighbor cells, a new cell is born in
the empty spot in the next generation.
Playing the game consists of setting up an initial configuration of cells to see what they
do and trying to create arrangements that grow rather than die out. When people first
began playing
Life
, they quickly discovered that it displayed a number of emergent prop-
erties even though it had such simple rules. Certain patterns of cells (called
gliders
)
could move across the grid, and some (
glider guns
) could even generate an endless
stream of new cells.
Artificial Pets
Artificial pets
make up one subcategory of artificial life games. These simulated
animals live on your computer (or mobile device), either in an environment of
their own or on your desktop. They can be simulations of real animals, as in the
Nintendogs
game for the Nintendo DS, or fantasy ones like the Tamagotchi that
inhabit a tiny and very simple electronic game built into a keychain.
Artificial pets are almost always cute. The gameplay concentrates on training, car-
ing for, and watching the creatures do endearing things. They seldom reproduce
or die (although there are exceptions, and sometimes they run away if you ignore
them or mistreat them), and the player usually wants to interact with only one or
two at a time. (The section “Genetic A-Life Games,” later in this chapter, discusses
games about whole populations of organisms in which individuals do reproduce
and die.)
If the player is going to spend much time looking at an artificial pet, then the pet
needs to have quite a lot of AI: a variety of things that stimulate it and behaviors
that it exhibits. An artificial pet should have a number of emotions or moods that
manifest themselves through the pet's behavior. The player should be able to tell,
by observation, how the pet is feeling and to influence its feelings by interacting
with it in different ways. The animal also needs to interact meaningfully with oth-
ers of its own kind: teasing, playing, grooming, fighting, and so on. Above all, it
needs to be able to learn, so there must be a way for the player to show it how to do
