Rank and File Chess

In Rank and File Chess, each move must be made from a player's most crowded Rank or File. The idea for this CV first appeared in a 2008 comment for the article "91.5 Trillion".

To categorize a bit, Frolov has a somewhat related concept in a more recent CV: Move-As-Square-Says.

The earlier version: Localization.

Setup

It is played with a standard 64-square board with Rook, Knight, Bishop, Queen, King, and Pawns. For a subvariant, substitution of a short-range piece for either the Bishop or Rook is recommended. For example, play with Mastodons (Pashas) in place of Rooks -- see: Mastodon Chess. The Rank and File Mutator is widely applicable, and mere convenience here describes the chief embodiment with the F.I.D.E. setup.

Pieces

Rules

Each turn, the player may move only from his own most crowded Rank or File. This is measured in terms of how many of a player's pieces and Pawns are on a Rank or File. The positions of opponent units (pieces or Pawns) is never a factor in the determination. So, each player may move only from the Rank or File having the most units from his own side. In case of a tie, File has precedence over Rank, and the player must move accordingly. In other words, suppose Rank 3 has 4 units, and File 7 has 4 units, then the player has to move from File 7, and no move from Rank 3 is permitted -- except of course from the one intersection square g3. In case of a tie between two Files, a player is permitted to move from either. There is no other criterion to separate tied Files. For example, if Files 2 and 8 both have a topmost 3 units from the player's side, any of those six are permitted to move. Likewise, in case of a tie between two Ranks, the player is allowed to move from either. In an endgame example, Ranks 2, 3, and 5 all have two, and no File has more than one, then play requires that one of the six Units in Ranks 2, 3 and 5 be moved.

When a King is checked, it may move out of Check regardless of which Rank or File is most crowded. However, when in Check, a player may not interpose or capture with a piece or Pawn unless it is moved from a square having the Rank/File precedence for the turn. By the same token, a piece or Pawn is not giving Check at all unless its move is otherwise legal in this game. The same applies to the King's escape square. A King may move into what would be Check in Chess if the attacker is barred from moving there by the rules of this game.

Notes

In practice, just a glance tells which Rank or File to move from. It does not take counting all of them, just a quick look to see where the most pieces and Pawns are. There will be much jockeying to get a Rank or File having the most pieces and Pawns so that the player may move from it -- or at least play to get a tie in numbers, thereby allowing play from the particular Rank or File. Anywhere from one to all 32 White or Black Units may be moved per turn depending on the existing present position. Initially, White may move any of the 16 White men, because Ranks 1 and 2 are tied at eight. On White's second move, White will have to move a piece if he has moved a Pawn, or vice versa, because the most crowded Rank will be the one he didn't move from last time.