Colorful Osmosis Chess

Colorful Osmosis Chess uses four basic piece types (plus Kings and Pawns). Two basic pieces are colorbound and two are colorswitching. Of the colorbound pieces, one is a slider and the other is a leaper; likewise for the colorswitching pieces. Basic pieces can create compond pieces by capturing enemy pieces, in some games this process is called absorbtion, here I use the synonym osmosis. Colorful Osmosis Chess is played on a ten-by-ten board.

Setup

White's  pieces are set up  as follows: Camels on the corners. From left to right on the second rank are Harvestman, Knight,  Bishop, Guard, King, Bishop, Knight, and Harvestman. On the third rank are ten Pawns, Black's army is placed in mirror symmetric positions  on the eighth, ninth, and tenth ranks.

Pieces

• King moves as an FIDE King but cannot castle.
• Guard moves as a non-royal King.
• Pawn moves as an FIDE Pawn including en passant. Pawns promote on the enemy next-to-last rank a non-royal piece (other than another Pawn). This gives 11 promotion choices.

Basic Pieces

• Bishop moves as an FIDE Bishop. The colorbound slider.
• Knight moves as an FIDE Knight. The colorswitching leaper.
• Camel moves two squares horizontally or vertically and one square diagonally or one square diagonally and two squares horizontally or vertically, leaping over occupied squares. The colorbound leaper.
• Harvestman moves one square horizontally or vertically then may continue as a Crooked Bishop (https://www.chessvariants.com/piececlopedia.dir/crookedbishop.html). The colorswitching slider.

Compound Pieces

• Cardinal moves as a Bishop or a Kinght.
•  Caliph moves as a Bishop or a Camel.
•  Evangelist moves as a Bishop or a Harvestman.
•  Gnu moves as a Knight or a Camel.
•  Battlemaster moves as a Knight or a Harvestman.
•  Imam moves as a Camel or a Harvestman.

Rules

The usual FIDE checkmate, stalemate, triple repetition and fifty-move rules apply. In addition, promotion is not limited to Pawns.Basic pieces may promote as follows:

1. Capturing a Pawn, Guard, or the corresponding basic piece does not cause promotion.
2. Capturing any other basic piece resuls in promotion to the compund piece with the combined move of captor and captive.
3. Capturing a compound piece which shares the captor's move results in promotion to the piece captured (in essence the captive swiches sides).
4. Capturing a compound piece which does not share the captor's move results in promotion to a compound piece combing the captor's move with one of but not both of the captive's basic moves. (Capturing player chooses.)

This process of promotion by capture is called osmosis.

Notes

Colorful Osmosis Chess began as an effort to use both colorbound and colorswiching sliders and leapers. Three of them are Bishop, Knight, and Camel. For the fourth basic piece I used Jörg Knappen's Harvestman from his Seenschach.  The osmosis rules are adapted from the assimilation rules of Fergus Duniho's Assimilation Chess with the following changes:

• Kings do not participate in osmosis.
• Compound pieces do not split.

The abscence of castling, Pawn promotion before the last rank, and especially the promotion of non-Pawn pieces is reminiscent of Shogi. Osmosis (promotion by captute) is found in several large Shogi variants such as Maka Dai Dai Shogi as well as Assimilation Chess.

Last revised by Ben Reiniger.