public int findGroundLevel()
    {
        if (_groundLevel != 0)
            return _groundLevel;
        
        for (int y = _height-1; y > 0; y--)
        {
            int counter = 0;
            for (int x = 0; x < _width; x++)
            {
                if (_class[y][x] == GROUND)
                    counter++;
            }
            if (counter < _width * 0.8)
            {
                _groundLevel = y;
                break;
            }
        }
        return _groundLevel;
    }