function Board(rows, cols) {
      this.rows = rows;
      this.cols = cols;
      this.elements = [];
    }

    Board.prototype.createBoard = function () {
      var board = document.createElement('div');
      board.className = "board";

      for (var i = 0; i < this.rows; i++) {
        var row = document.createElement('div');
        row.className = "row";

        for (var j = 0; j < this.cols; j++) {
          var element = document.createElement('div');
          element.className = "element";
          row.appendChild(element);
          this.elements.push(element);
        }

        board.appendChild(row);
      }

      document.body.appendChild(board);
    };

    Board.prototype.watchMove = function (callback) {
      for (var index in this.elements) {
        this.elements[index].addEventListener('click', callback)
      }
    };

    Board.prototype.getElements = function () {
      return this.elements;
    };

    function SimpleAI(board) {
      this.board = board;
    }

    SimpleAI.prototype.handleMove = function () {
      var elements = this.board.getElements();

      for (var i = 0; i < elements.length; i++) {
        if (elements[i].innerHTML === "") {
          elements[i].innerHTML = "O";
          break;
        }
      }
    };

    var board = new Board(3, 3);
    board.createBoard();

    var simpleAI = new SimpleAI(board);
    var aiMoveCallback = simpleAI.handleMove.bind(simpleAI);
    var playerMoveCallback = function (e) {e.target.innerHTML = 'X';};

    board.watchMove(playerMoveCallback);
    board.watchMove(aiMoveCallback);