public static Rank RelativeRank(this Rank rank, Player color) => rank.ToInt() ^ (color.Side * 7);
public static char RankChar(this Rank r) => RankChars[r.ToInt()];
public static string RankString(this Rank r) => RankStrings[r.ToInt()];
public static BitBoard BitBoardRank(this Rank r) => RankBB[r.ToInt()];