private static bool Marked(int x, int y)
        {
            const int patternHeight = 4;
            const int patternWidth = 3;

            var posX = x % patternWidth;
            var posY = y % patternHeight;

            if (posY == 0)
                return false;

            if (posX == 0 && posY != patternHeight - 1)
                return false;

            if (posY == 1 && posX == 1)
                return false;

            return true;
        }