void OnMouseOver()
{
if (Input.GetMouseButtonDown(0))
{
GameObject board = GameObject.Find("TicTacToe_Board");
TicTacToe boardScript = board.GetComponent <TicTacToe>();
if (boardScript.AvailableSlot(gridIndex))
{
boardScript.PlayTurn(gridIndex, TicTacToe.whosTurn);
}
}
}