// Just slightly modified from:

​

// Daniel Shiffman

// http://codingtra.in

// http://patreon.com/codingtrain

​

// Game of Life

// Video: https://youtu.be/FWSR_7kZuYg

​

function make2DArray(cols, rows) {

  let arr = new Array(cols);

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

    arr[i] = new Array(rows);

  }

  return arr;

}

​

let grid;

let cols;

let rows;

let resolution = 10;

let running = false;

​

function setup() {

  createCanvas(600, 400);

  cols = width / resolution;

  rows = height / resolution;

​

  grid = make2DArray(cols, rows);

  for (let i = 0; i < cols; i++) {

    for (let j = 0; j < rows; j++) {

      grid[i][j] = 0;

    }

  }

}

​

function draw() {

  background(0);

​

  for (let i = 0; i < cols; i++) {

    for (let j = 0; j < rows; j++) {

      let x = i * resolution;

      let y = j * resolution;

      if (grid[i][j] == 1) {

        fill(255);

        stroke(0);

        rect(x, y, resolution - 1, resolution - 1);

      }

    }

  }

  if (!running) {

    if (mouseIsPressed) {

      grid[floor(mouseX/resolution)][floor(mouseY/resolution)] = 1;

    }

  } else {

    let next = make2DArray(cols, rows);

​

    // Compute next based on grid

    for (let i = 0; i < cols; i++) {

      for (let j = 0; j < rows; j++) {

        let state = grid[i][j];

        // Count live neighbors!

        let sum = 0;

        let neighbors = countNeighbors(grid, i, j);

​

        if (state == 0 && neighbors == 3) {

          next[i][j] = 1;

        } else if (state == 1 && (neighbors < 2 || neighbors > 3)) {

          next[i][j] = 0;

        } else {

          next[i][j] = state;

        }

      }

    }

​

    grid = next;

  }

}

​

function countNeighbors(grid, x, y) {

  let sum = 0;

  for (let i = -1; i < 2; i++) {

    for (let j = -1; j < 2; j++) {

      let col = (x + i + cols) % cols;

      let row = (y + j + rows) % rows;

      sum += grid[col][row];

    }

  }

  sum -= grid[x][y];

  return sum;

}

​

function keyPressed() {

  running = true;

  frameRate(2);

​

}

​