Create your own Cellular Automata!

README

Hello! To create your own cellular automata, you must provide the code for a function that acts on each cell. The language must be javascript.

The function will be called on each cell to get the value of the cells new state. Whatever you return will determine the new value of the cell.

All you have to do is return a boolean (true or false) value. This value determines whether the cell will be colored black (false) or white (true).

Since this is a cellular automata, each cells new value depends on its previous value, as well the value of its neighbors. For this reason, 2 values are exposed to you:

cell.value and cell.neighbors

cell.value is a boolean representing the value of the current cell.

cell.neighbors is an array of booleans representing the values of cell's neighbors. Since each cell has 8 neighbors, the array indices are laid out like this: 0,1,2 are top-left, top-middle, and top-right respectively. 3,4 are middle-left and middle-right. There is no middle-middle in the neighbors array, because middle-middle would be the current cell! 5,6,7 are bottom-left, bottom-middle, and bottom-right. Visually, it would look like this:

0	1	2
3	cell	4
5	6	7

In summary, to access the cells top-left neighbor, you would write cell.neighbors[0]. To refer to the cells bottom-middle neighbor, you would write cell.neighbors[6]. Remember, to refer to the cell itself, just write 'cell'.

Example: Conway's Game of Life

You may have recognized the default animation as Conway's game of life. How does this work? The rules for this particular automata are as follows:

• Any live cell with fewer than two live neighbours dies, as if caused by underpopulation.
• Any live cell with two or three live neighbours lives on to the next generation.
• Any live cell with more than three live neighbours dies, as if by overpopulation.
• Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction.

Notice how each rule simply refers to the number of alive neighbors. Thus, the first thing we do is grab a count of our alive neighbors. We will decide that alive is represented by the value true, and dead as the value false.

const neighbors_alive = cell.neighbors.filter(neighbor => neighbor.value).length

We filtered out all the falses from the neighbors array, and then grabbed the length property. Now we can do comparisons like neighbors_alive === 3 and such.

Now that we have the number of alive neighbors, we can implement the rules for Conway's GoL with a logical expression:

const alive = cell.value

return (!alive && neighbors_alive === 3) || (alive && (neighbors_alive === 2 || neighbors_alive === 3))

Have fun creating your own cellular automata! Click the Show/Hide button below to get back to the code editor.