// The Coding Train / Daniel Shiffman

// https://thecodingtrain.com/challenges/179-wolfram-ca

// https://youtu.be/Ggxt06qSAe4

​

// Array to store the state of each cell.

let cells = [];

// Rule value

let ruleValue = 90;

// The ruleset string

let ruleSet;

// Width of each cell in pixels

let w = 16;

// y-position

let y = 0;

​

function setup() {

  createCanvas(600, 600);

​

  // Convert the rule value to a binary string.

  ruleSet = ruleValue.toString(2).padStart(8, "0");

​

  // Calculate the total number of cells based on canvas width.

  let total = width / w;

  // Initialize all cells to state 0 (inactive).

  for (let i = 0; i < total; i++) {

    cells[i] = 0;

  }

  // Set the middle cell to state 1 (active) as the initial condition.

  cells[floor(total / 2)] = 1;

  background(255);

}

​

function draw() {

  // Draw each cell based on its state.

  for (let i = 0; i < cells.length; i++) {

    let x = i * w;

    noStroke();

    fill(255 - cells[i] * 255);

    square(x, y, w);

  }

​

  // Move to the next row.

  y += w;

​

  // Prepare an array for the next generation of cells.

  let nextCells = [];

​

  // Iterate over each cell to calculate its next state.

  let len = cells.length;

  for (let i = 0; i < len; i++) {

    // Calculate the states of neighboring cells

    let left = cells[(i - 1 + len) % len];

    let right = cells[(i + 1) % len];

    let state = cells[i];

    // Set the new state based on the current state and neighbors.

    let newState = calculateState(left, state, right);

    nextCells[i] = newState;

  }

​

  // Update the cells array for the next generation.

  cells = nextCells;

}

​

function calculateState(a, b, c) {

  // Create a string representing the state of the cell and its neighbors.

  let neighborhood = "" + a + b + c;

  // Convert the string to a binary number

  let value = 7 - parseInt(neighborhood, 2);

  // Return the new state based on the ruleset.

  return parseInt(ruleSet[value]);

}

​