let gap = 100;

let grid = [];

let current;

​

function setup() {

  createCanvas(600, 600);

  cols = floor(width / gap);

  rows = floor(height / gap);

​

  for (let x = 0; x < rows; x++) {

    for (let y = 0; y < cols; y++) {

      let cell = new Cell(y, x);

      grid.push(cell);

    }

  }

​

  current = grid[0];

  // frameRate(5);

}

​

function draw() {

  background(0);

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

    grid[i].show();

  }

  current.visited = true;

  current.highlight();

  let nextCell = current.checkNeighbors();

  if(nextCell){

    nextCell.visited = true;

    removeWalls(current, nextCell);

    current = nextCell;

  }

}

​

function index(x, y) {

   if (x < 0 || y < 0 || x > cols - 1 || y > rows - 1) {

    return -1;

  }

  return x + y * cols;  // algorithm to get the index in an array (grid)

}

​

function removeWalls(current, nextCell){

  let posX = current.x - nextCell.x;

  let posY = current.y - nextCell.y;

  if(posX === 1){

    current.walls[3] = false;

    nextCell.walls[1] = false;

  }

  if(posX === -1){

    current.walls[1] = false;

    nextCell.walls[3] = false;

  }

  if(posY === 1){

    current.walls[0] = false;

    nextCell.walls[2] = false;

  }

  if(posY === -1){

    current.walls[2] = false;

    nextCell.walls[0] = false;

  }

}

​

class Cell {

  constructor(x, y) {

    this.x = x;

    this.y = y;

    this.walls = [true, true, true, true];

    this.visited = false;

  }

  show() {

    stroke(255);

    let x = this.x * gap;

    let y = this.y * gap;

​

    if (this.walls[0]) {

      line(x, y, x + gap, y);

    }

    if (this.walls[1]) {

      line(x + gap, y, x + gap, y + gap);

    }

    if (this.walls[2]) {

      line(x + gap, y + gap, x, y + gap);

    }

    if (this.walls[3]) {

      line(x, y + gap, x, y);

    }

    if (this.visited) {

      noStroke();

      fill(random(255), random(255), random(255), 25);

      rect(x, y, gap, gap);

    }

  }

  checkNeighbors() {

    let neighbors = [];

    let top = grid[index(this.x, this.y - 1)];

    let right = grid[index(this.x + 1, this.y)];

    let bottom = grid[index(this.x, this.y + 1)];

    let left = grid[index(this.x - 1, this.y)];

​

    if (top && !top.visited) {

      neighbors.push(top);

    }

    if (right && !right.visited) {

      neighbors.push(right);

    }

    if (bottom && !bottom.visited) {

      neighbors.push(bottom);

    }

    if (left && !left.visited) {

      neighbors.push(left);

    }

    if(neighbors.length > 0){

      let randy = floor(random(0,neighbors.length));

      return neighbors[randy];

    } else {

       return undefined;

    }

  }

  highlight(){

    fill(100,100,250);

    rect(this.x*gap, this.y*gap, gap);

  }

}

​