let arr = new Array(cols);

​

  for (let i = 0; i < cols; i++) {

    arr[i] = new Array(rows);

  }

​

  return arr;

}

​

let grid;

let cols;

let rows;

let res = 10;

let USER = 0;

let RUN = 1;

let STATE = USER;

​

function setup() {

  createCanvas(900, 600);

  frameRate(30);

  cols = width / res;

  rows = height / res;

  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(255);

​

  for (let i = 0; i < cols; i++) {

    for (let j = 0; j < rows; j++) {

      let x = i * res;

      let y = j * res;

      stroke(127);

      if (grid[i][j]) {

        fill(0);

      } else {

        fill(255);

      }

      rect(x, y, res, res);

    }

  }

​

  if (STATE == RUN) {

    let next = make2DArray(cols, rows);

​

    for (let i = 0; i < cols; i++) {

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

        let state = grid[i][j];

        let sum = 0;

        let neighbours = countNeighbours(grid, i, j);

​

        if (!state && neighbours == 3) {

          next[i][j] = 1;

        } else if (state && (neighbours < 2 || neighbours > 3)) {

          next[i][j] = 0;

        } else {

          next[i][j] = state;

        }

      }

    }

    grid = next;

  }

  fill(0, 127);

  rect(0, 0, 200, 40);

  textSize(20);

  fill(0, 255, 0);

  if (STATE == USER) {

    text("User designing cells", 10, 27.5);

  } else {

    text("Running simulation", 10, 27.5);

  }

}

​

function countNeighbours(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() {

  if (key == " ") {

    STATE = !STATE;

  }

  if (key == "r") {

    for (let i = 0; i < cols; i++) {

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

        grid[i][j] = floor(random(2));

      }

    }

    STATE = RUN;

  }

  if (key == "c") {

    for (let i = 0; i < cols; i++) {

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

        grid[i][j] = 0;

      }

    }

    STATE = USER;

  }

}

​

function mousePressed() {

  if (STATE == USER) {

    let mx = floor(mouseX / res);

    let my = floor(mouseY / res);

    grid[mx][my] = !grid[mx][my];

  }

}