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## WHAT IS IT?  IT IS AWESOME!
This program is an example of a twodimensional cellular automaton. This particular cellular automaton is called The Game of Life.
A cellular automaton is a computational machine that performs actions based on certain rules. It can be thought of as a board which is divided into cells (such as square cells of a checkerboard). Each cell can be either "alive" or "dead." This is called the "state" of the cell. According to specified rules, each cell will be alive or dead at the next time step.
for info go here: http://en.wikipedia.org/wiki/Day_%26_Night
## HOW IT WORKS
The rules of the game are as follows. Each cell checks the state of itself and its eight surrounding neighbors and then sets itself to either alive or dead. If there are less than two alive neighbors, then the cell dies. If there are more than three alive neighbors, the cell dies. If there are 2 alive neighbors, the cell remains in the state it is in. If there are exactly three alive neighbors, the cell becomes alive. This is done in parallel and continues forever.
There are certain recurring shapes in Life, for example, the "glider" and the "blinker". The glider is composed of 5 cells which form a small arrowheaded shape, like this: O O OOO
This glider will wiggle across the world, retaining its shape. A blinker is a block of three cells (either up and down or left and right) that rotates between horizontal and vertical orientations.
## HOW TO USE IT
The INITIALDENSITY slider determines the initial density of cells that are alive. SETUPRANDOM places these cells. GOFOREVER runs the rule forever. GOONCE runs the rule once.
If you want to draw your own pattern, use the DRAWCELLS button and then use the mouse to "draw" and "erase" in the view.
## THINGS TO NOTICE
Find some objects that are alive, but motionless.
Is there a "critical density"  one at which all change and motion stops/eternal motion begins?
## THINGS TO TRY
Are there any recurring shapes other than gliders and blinkers?
Build some objects that don't die (using DRAWCELLS)
How much life can the board hold and still remain motionless and unchanging? (use DRAWCELLS)
The glider gun is a large conglomeration of cells that repeatedly spits out gliders. Find a "glider gun" (very, very difficult!).
## EXTENDING THE MODEL
Give some different rules to life and see what happens.
Experiment with using neighbors4 instead of neighbors (see below).
## NETLOGO FEATURES
The neighbors primitive returns the agentset of the patches to the north, south, east, west, northeast, northwest, southeast, and southwest. So `count neighbors with [living?]` counts how many of those eight patches have the `living?` patch variable set to true.
`neighbors4` is like `neighbors` but only uses the patches to the north, south, east, and west. Some cellular automata, like this one, are defined using the 8neighbors rule, others the 4neighbors.
## RELATED MODELS
Life TurtleBased  same as this, but implemented using turtles instead of patches, for a more attractive display
## CREDITS AND REFERENCES
The Game of Life was invented by John Horton Conway.
See also:
Von Neumann, J. and Burks, A. W., Eds, 1966. Theory of SelfReproducing Automata. University of Illinois Press, Champaign, IL.
"LifeLine: A Quarterly Newsletter for Enthusiasts of John Conway's Game of Life", nos. 111, 19711973.
Martin Gardner, "Mathematical Games: The fantastic combinations of John Conway's new solitaire game `life',", Scientific American, October, 1970, pp. 120123.
Martin Gardner, "Mathematical Games: On cellular automata, selfreproduction, the Garden of Eden, and the game `life',", Scientific American, February, 1971, pp. 112117.
Berlekamp, Conway, and Guy, Winning Ways for your Mathematical Plays, Academic Press: New York, 1982.
William Poundstone, The Recursive Universe, William Morrow: New York, 1985.
## HOW TO CITE
In other publications, please use:
## COPYRIGHT NOTICE
Permission to use, modify or redistribute this model is hereby granted, provided that both of the following requirements are followed:
This model was created as part of the project: CONNECTED MATHEMATICS: MAKING SENSE OF COMPLEX PHENOMENA THROUGH BUILDING OBJECTBASED PARALLEL MODELS (OBPML). The project gratefully acknowledges the support of the National Science Foundation (Applications of Advanced Technologies Program)  grant numbers RED #9552950 and REC #9632612.
This model was converted to NetLogo as part of the projects: PARTICIPATORY SIMULATIONS: NETWORKBASED DESIGN FOR SYSTEMS LEARNING IN CLASSROOMS and/or INTEGRATED SIMULATION AND MODELING ENVIRONMENT. The project gratefully acknowledges the support of the National Science Foundation (REPP & ROLE programs)  grant numbers REC #9814682 and REC0126227. Converted from StarLogoT to NetLogo, 2001. 
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