var w = 10;

var grid = [];

var stack = [];

var current;

​

function setup() {

  var wid = round(window.innerWidth / w) * w;

  var hei = round(window.innerHeight / w) * w;

  createCanvas(wid, hei);

  cols = floor(width / w); //i

  rows = floor(height / w); //j

​

  for(var j = 1; j < rows - 1; j++) {

    var temp = [];

    for(var i = 1; i < cols - 1; i++) {

      var cell = new Cell(i, j);

      temp.push(cell);

    }

    grid.push(temp);

  }

​

  current = grid[0][0];

}

​

function draw() {

  background(51);

​

  for(var j = 0; j < grid.length; j++) {

    for(var i = 0; i < grid[0].length; i++) {

      grid[j][i].display();

    }

  }

​

  current.visited = true;

  current.highlight();

​

  //STEP 1

  var next = current.checkNeighbors();

  if (next) {

    next.visited = true;

    //STEP 2

    stack.push(current)

    //STEP 3

    removeWalls(current, next);

    current = next;

  } else if (stack.length > 0) {

    current = stack.pop();

  }

}

​

function Cell(i, j) {

  this.i = i - 1;

  this.j = j - 1;

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

  this.visited = false;

​

  this.highlight = function() {

    var x = (this.i + 1) * w;

    var y = (this.j + 1) * w;

    noStroke();

    fill(50, 255, 50);

    rect(x, y, w, w);

  }

​

  this.checkNeighbors = function() {

    var neighbors = [];

    if (this.j > 0) {

      var top = grid[this.j - 1][this.i];

      if (!top.visited) {

        neighbors.push(top);

      }

    }

    if (this.i < cols - 3) {

      var right = grid[this.j][this.i + 1];

      if (!right.visited) {

        neighbors.push(right);

      }

    }

    if (this.j < rows - 3) {

      var bottom = grid[this.j + 1][this.i];

      if (!bottom.visited) {

        neighbors.push(bottom);

      }

    }

    if (this.i > 0) {

      var left = grid[this.j][this.i - 1];

      if (!left.visited) {

        neighbors.push(left);

      }

    }

​

    if (neighbors.length > 0) {

      var r = floor(random(0, neighbors.length));

      return neighbors[r];

    } else {

      return undefined;

    }

  }

​

  this.display = function () {

    var x = (this.i + 1) * w;

    var y = (this.j + 1) * w;

    var xw = x + w;

    var yw = y + w;

    stroke(255);

    if (this.walls[0]) {

      line(x, y, xw, y);

    }

    if (this.walls[1]) {

      line(xw, y, xw, yw);

    }

    if (this.walls[2]) {

      line(xw, yw, x, yw);

    }

    if (this.walls[3]) {

      line(x, yw, x, y);

    }

​

    if (this.visited) {

      noStroke();

      fill(255, 0, 255, 100);

      rect(x, y, w, w)

    }

  }

}

​

function removeWalls(a, b) {

  var x = a.i - b.i;

  if (x === 1) {

    a.walls[3] = false;

    b.walls[1] = false;

  }

  if (x === -1) {

    a.walls[1] = false;

    b.walls[3] = false;

  }

  var y = a.j - b.j

  if (y === 1) {

    a.walls[0] = false;

    b.walls[2] = false;

  }

  if (y === -1) {

    a.walls[2] = false;

    b.walls[0] = false;

  }

}

​