constructor(x, y, w, n) {

    this.x = x;

    this.y = y;

    this.n = n;

    this.w = w;

  }

  show() {

    fill("#AAA");

    square(this.x, this.y, this.w);

    fill("#000");

    textAlign(CENTER, CENTER);

    text(this.n, this.x + this.w / 2, this.y + this.w / 2);

  }

  clicked(x, y, empty) {

    if (!(x < this.x || x > this.x + this.w || y < this.y || y > this.y + this.w)) {

      x = empty.x;

      y = empty.y

      if (!((this.x - this.w === x || this.x + this.w === x) && (this.y - this.w === y || this.y + this.w === y))) {

        const oldPos = {x: this.x, y: this.y}

        this.x = x

        this.y = y

        return oldPos;

      }

    }

    return null;

  }

}