That's Life!

Cells. Life. Birth. Multiplication. Evolution. Death. This is the basis of the Game of Life, created by the mathematician John Conway. A solo game, in which the Creator introduces an initial form of life, a mere set of cells, and then becomes the Observer, applying the laws governing this world, and determining the development of these cells.

The American programmer Don Woods, a fan of games, turned this solo life into a life requiring two to play. With, not one, but two populations, represented by different colors. And with a profound change: the evolution no longer takes place in isolation; each player adds a new element to his own population, an immigrant, every 10 generations. A very limited action, in space and time, but with the potential for causing a global and long term effect! It becomes thus possible to try to rebalance, unbalance or stabilize populations. But it is also possible that the result is full extinction, arising before the possibility of a new intervention. This game is called Immigration.

Let's move on to the laws of Life. The fate of each individual only depends on the number of neighbors in the eight surrounding spaces, whatever the population to which they belong:

Death by isolation: zero or one neighbour.
Survival: two or three neighbours.
Death by overpopulation: four or more neighbours.

And there are also Births: the emergence of a new individual in each empty space that has, exactly, three neighbours. This new individual will belong to the population that has the majority in this neighbourhood.

Deaths and births are considered simultaneous events. So, they just have an effect on the ensuing generation (turn) neighbourhood count.

An initial position

Red: Deaths. Blue: Births.

To play you need a large board with a grid, preferably more than a Go Board (19 x 19); enough markers  of two colors to represent the populations; additional markers in another two colours, to mark births and deaths; a marker for keeping track of generations (or a sheet of paper).

Setup: players place, alternately, 5 members of their own population.

In each generation, perform the following actions, covering all elements of the populations already on the board,  and all empty spaces, in a systematic way to avoid errors:

1) Mark the pieces having 0 or 1 neighbors (deaths by isolation) or more than 3 (deaths by overpopulation);
2) Mark, in a different colour, the spaces with 3 neighbours (births);
3) Place new population tokens (births) of equal colour to that of the majority population surrounding the space;
4) Remove the deceased parts.

Immigration: every 10 generations, each player adds a new element to his population, placing it in an empty space of his choice, starting with the player with the larger population. In order to provide a better balance, it may be preferable to invert the order.

Win: when there is only one population left at an Immigration moment.

Draw: both populations have gone extinct between two moments of immigration. 

You may try other rules, for example, assigning a draw when a stable form (which does not generate births or deaths) is reached, or, in this case, assigning victory to the larger population.

The solo game can be used as a first approach, and to an introduction to the patterns that emerge:

Stable forms, still life, not generating births nor deaths.

Oscillators, periodically alternating between two shapes.

Shapes that seem to move across the board.

Formations that quickly become extinct.

Two still life forms and two oscillators

References

Berloquin, Pierre (1981), Découvrez … la vie, seul ou à deux, Jeux & Stratégie, n.º 9, Junho-Julho.

Don Woods, http://www.icynic.com/~don/

Gardner, Martin (1970), MATHEMATICAL GAMES - The fantastic combinations of John Conway's new solitaire game "life", Scientific American 223: 120-123.
http://www.ibiblio.org./lifepatterns/october1970.html