Theoretically, "X" and "O" clearly represent the "opposite", which can never be matched. But in the real world we live in, it does not seem to be. At some point, "X" may become "O", and at another point "O" may be "X". I think this is a situation that often happens in reality. Thus, in reality, I tried to express in my piece the thought that a lot of "X" and "O" are mixed.