© Irmen de Jong
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This has been inspired by Stephen Wolfram's cellular automata experiments that he did in his book "A new kind of Science" (example).
How does this work?
What you see on the screen when you press "Run", is the evolution of a one-dimensional (linear) cellular automaton, where every new generation is displayed on a line below the previous generation. "Time" runs on the vertical axis, top-to-bottom.
The automaton consists of a (large) number of cells sitting on a single line next to eachother. These cells can have a value, or status, that varies according to a set of simple rules. Those rules say what the value of the cell should be in the new generation, depending on the current value.
Binary valued cells
In this automaton, a cell can have one of two values: black or white. The rules tell if the cell should be black or white next, depending on the values of the cell itself and both neighbor cells in the previous generation. For instance:
XX XX XX (the previous generation) XX (the new cell value) This rule says "the new value of the cell should be black if in the previous generation, the cell itself was white, and the left and right neighbor were black". There are eight unique combinations of three cells, so this automaton has 23=8 rules that describe it fully.
Ternary valued cells
In this automaton, a cell can have one of three values: black , grey or white. The rules tell if the cell should be black or grey or white next, depending on the average values of the cell itself and both neighbor cells in the previous generation. For instance:
XXXXXXX (the previous generation) XX XX XX (the new cell value) This rule says "the new value of the cell should be white if in the previous generation, the average shade of grey of the cell and both neighbor cells was this shade of grey.
There are seven average shades of grey of three cells (black to white), so this automaton needs seven rules to describe it fully.