Decimaka

Decimaka is a western Chess variant that tries to emulate the promotion dynamics of the historic Japenese Chess game 'Maka Dai Dai Shogi'. In particular, promotion is not reserved for Pawns. Most piece types from the initial setup can promote, and the right to promote originates from making a capture, rather than reaching a promotion zone. So promotion can happen everywhere on the board.

This makes tactics highly non-trivial. It also impacts strategy, because promotion at the end of a game is not automatic, and in fact impossible if the opponent would not have any easy targets for capturing.

Note: a revised version of this game, with somewhat tweaked rules, is described here

Setup

Pieces

• King - moves as orthodox King. Takes 3 steps towards Rook on castling
• Queen (promoted Fiancee) - moves as orthodox Queen
• Lion - Moves as King, Knight or jumps 2 squares orthogonally or diagonally
• Star - Jumps one, two or three squares orthogonally or diagonally
• Trident (promoted Tee) - slides along files, or diagonally forward
• Nightrider (promoted Knight) - makes arbitrarily many Knight moves in the same direction, until blocked
• Rook - moves like orthodox Rook
• Bishop - moves like orthodox Bishop
• Knight - moves like orthodox Knight
• Fiancee - moves like orthodox King (but is not royal)
• Y - leaps one, two or three squares straight backward or diagonally forward
• Cross - steps one or jumps two squares in all orthogonal directions
• Tee - steps one square straight forward or backward, or diagonally forward
• Omni (promoted Pawn, Cross, Y, Star or Lion) - captures one step diagonally, moves without capturing one step orthogonally
• Pawn - moves like orthodox Pawn, including a double push from its initial location, and e.p. capture

Rules

The game is won by checkmating the opponent King. Stalemate is a draw.

Pieces can (and sometimes must) promote when they make a capture. This can happen anywhere on the board, there isn't any special promotion zone. Promotion is mandatory when you capture a promoted piece; otherwise it is optional, and you can elect not to promote.

A piece other than King which captures a Queen promotes to Queen in the same turn. That also applies to pieces that are already promoted, or would normally not promote at all.

Pawns that reach the final rank simply turn into dead wood there.

Notes

There are three classes of pieces, depending on how they promote:

• Unpromotable pieces (King, Rook, Bishop).
• Pieces that turn from steppers/leapers into the corresponding sliders/riders (Fiancee, Knight, Tee).
• Pieces that promote to Omni (Lion, Star, Y, Cross, Pawn). Which, for all but the latter, is actually a demotion.

Promotability has a huge affect on tactics. Where without it an exchange typically is most profitable whan you capture with the least-valuable piece first, with it you would try to end with the piece that has the best promotion. Furthermore, when you won't make the last capture yourself, you can sometimes try to discourage the opponent's recapture by promoting (if he can only recapture with a strongly demoting piece). Which is a reason to order unpromotable pieces earlier, even when they are more valuable.

Last revised by H. G. Muller.