Wormhole Chess

Michael Thompson

This is a variant chess board with an unusual topology. The name comes from the resemblance to the toy model of a wormhole in a 2D universe.

My rules for 2 players are the same as for standard chess with the following modifications: - Each player starts with 32 pieces instead of the usual 16, with one standard set of 16 pieces starting on each side of the board for each player. The topology of the board allows each standard set of 16 pieces for player 1 to face off against both standard set of 16 pieces for player 2 (and vice versa), one across the flat side (as in standard chess) and the other through the wormhole. - Each player still has only 1 king as in standard chess. This is achieved by substituting in a new piece, called a prince, where one of the two kings would usually start. The prince moves like a king (including castling) but is not royal (it can be taken like any other non-king piece, castling through check is allowed). A prince has 1 additional move available: if the king is not in check then a prince may swap positions with the king. This removes any castling rights from both pieces. A pawn may promote to a prince. - Pawns require a notion of forward. There is a reasonably intuitive notion of forward on most squares of the wormhole board. In some places (the pentagons) there are 2 forward directions where a pawn may move forward in 2 possible directions and attacks/defends 3. There are 8 squares within the wormhole where the "forward" direction is less obvious. I'd define each of these to also have 2 possible forward directions, matching the flow of the adjacent squares. However, arguing over this situation with your opponent is part of the fun of playing wormhole chess. - Sliding pieces (rooks / bishops / queens) have a choice whenever they slide through a pentagon: there are 2 possible directions in which their slide may continue, the two opposites to the side where they enter. - Knight moves near a pentagon use the same sliding rules as above when figuring out where they may move.

Other things to think about: - A standard chess board has 64 squares. How many does this one have? - Variants on the rules for 2 players? - A sensible set of rules for 4 players, each starting with a standard set of 16 pieces? - Knights tours? - Other chess puzzles translated to the context of a wormhole board? - To what extent do good openings in standard chess remain good openings in wormhole chess?

The idea for the board came from DaveMakesStuff but I designed and 3D printed my own version. My version is slightly larger, does not use any glue, and the magnets are not visible.