constructor(i, j) {

    // point

    this.i = i;

    this.j = j;

​

    // walls

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

​

    // direction

    this.TOP = 0;

    this.RIGHT = 1;

    this.BOTTOM = 2;

    this.LEFT = 3;

​

    // visited

    this.visited = false;

​

    // color

    this.color = [255, 0, 255, 100];

  }

  getAllNeighbors() {

    // undefined or Cell instance in array

    let neighbors = [];

​

    neighbors[this.TOP] = grid[this.index(this.i, this.j - 1)];

    neighbors[this.RIGHT] = grid[this.index(this.i + 1, this.j)];

    neighbors[this.BOTTOM] = grid[this.index(this.i, this.j + 1)];

    neighbors[this.LEFT] = grid[this.index(this.i - 1, this.j)];

​

    return neighbors;

  }

  getVisitedNeighborCount() {

    let cnt = 0;

    let neighbors = this.getAllNeighbors();

​

    for (let n of neighbors) {

      if(n != undefined && n.visited) {

        cnt++;

      }

    }

    return cnt;

  }

​

  highlight() {

    noStroke();

    fill(0, 255, 0);

    rect(this.i * w, this.j * w, w, w);

  }

​

  removeWalls(other) {

    let di = this.i - other.i;

    let dj = this.j - other.j;

​

    if (di === -1) {

      this.walls[this.RIGHT] = false;

      other.walls[other.LEFT] = false;

    } else if (di === 1) {

      this.walls[this.LEFT] = false;

      other.walls[other.RIGHT] = false;

    }

​

    if (dj === -1) {

      this.walls[this.BOTTOM] = false;

      other.walls[other.TOP] = false;

    } else if (dj === 1) {

      this.walls[this.TOP] = false;

      other.walls[other.BOTTOM] = false;

    }

  }

​

  index(i, j) {

    if (i < 0 || j < 0 || i > cols - 1 || j > rows - 1)

      return -1;

    else

      return i + (j * cols);

  }

​

  checkNeighbors() {

    let neighbors = this.getAllNeighbors();

    let able = []

​

    for (let n of neighbors) {

      if ((n != undefined) && (!n.visited) && (n.getVisitedNeighborCount() < 2)) {

        able.push(n);

      }

    }

​

    return random(able);

  }

​

  show() {

    let x = this.i * w;

    let y = this.j * w;

​

    stroke(255);

    noFill();

    // rect(x, y, w, w); 

    if (this.walls[this.TOP])

      line(x, y, x + w, y); // top

    if (this.walls[this.RIGHT])

      line(x + w, y, x + w, y + w); // right

    if (this.walls[this.BOTTOM])

      line(x, y + w, x + w, y + w); // bottom

    if (this.walls[this.LEFT])

      line(x, y, x, y + w); // left

​

​

    // paint color

    if (this.visited) {

      noStroke();

      fill(this.color);

      rect(x, y, w, w);

    }

​

​

  }

}