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This page is written by the game's inventor, Reinhard Scharnagl.

Capablanca Random Chess

by Reinhard Scharnagl


Board Image
Sample layout, graphics from SMIRF

This game was voted the winner of the Chess Variant Pages 10th aniversary design contest, submitted by the late Reinhard Scharnagl. It was created to extend the concepts of Fischer Random Chess to Capablanca's Chess. Specifically, it had the following goals:

  1. creating an interesting drosophila for chess programmers
  2. using Capablanca's 10x8 Chess board geometry
  3. using Capablanca's piece set (incl. archbishop and chancellor)
  4. applying rules aligned to Fischer Random Chess
  5. avoid violating any patents


At the start of the game, a randomized setup is selected with the following restrictions:

  1. The Bishops must be on different colored squares.
  2. The King must be placed between the Rooks to allow castling.
  3. All Pawns must be protected.

This Interactive Diagram will randomize the position when you click Restart after first clicking Play It! While it should abide by the first two restrictions, it may not abide by the third. In that case, click Restart again until the position is legal.

files=10 ranks=8 promoZone=1 promoChoice=NBRQAC graphicsDir=/play/pbm/showpiece.php?size=50%26set=magnetic%26piece= whitePrefix=W blackPrefix=B squareSize=50 lightShade=#EEEECC darkShade=#226822 shuffle=QA,N!BR!AC!QK pawn:P:ifmnDfmWfceF:P:a2,b2,c2,d2,e2,f2,g2,h2,i2,j2,,a7,b7,c7,d7,e7,f7,g7,h7,i7,j7 knight:N:N:N:c1,h1,,c8,h8 bishop:B:B:B:d1,g1,,d8,g8 rook:R:R:R:a1,j1,,a8,j8 queen:Q:Q:Q:e1,,e8 archbishop:A:BN:A:b1,,b8 chancellor:C:RN:M:i1,,i8 king:K:KisO3:K:f1,,f8


The rules to CRC are as follows:

a) creating a starting position (one of 48.000):

  1. the bishops have to be placed upon different colored squares; same rule applies to the implicite bishop pieces: queen and archbishop (aligned to FRC)
  2. the king always has to be placed somewhere between the rooks to enable castlings (aligned to FRC)
  3. use only such positions without unprotected pawns (Chess)
b) describing a method of generating starting positions on free squares by using a dice or random number generator:
  1. select queen or the archbishop to be placed first (2x)
  2. place the selected 1st piece upon a bright square (5x)
  3. place the selected 2nd piece upon a dark square (5x)
  4. one bishop has to be placed upon a bright square (4x)
  5. one bishop has to be placed upon a dark square (4x)
  6. one chancellor has to be placed upon a free square (6x)
  7. one knight has to be placed upon a free square (5x)
  8. one knight has to be placed upon a free square (4x)/2
  9. set the king upon the center of three free squares left
  10. set the rooks upon the both last free squares left
  11. this establishes White's first row, the Black side has to be built up symmetrically to this
  12. place ten pawns similar to traditional chess in a row
  13. skip spositions that have unprotected pawns or violate any patent.
  14. thus there exists a fixed correlation number to position

c) nature of (asymmetric Fischer-) castlings:

  1. castlings are (like in traditional chess) only valid if neither the affected king or rook has been moved, or there would be a need to jump over any third piece, or the king would be in chess somewhere from his starting position to his target field (both included). Therefore all squares between king and its target square (included) have to be free from third pieces, same applies to the way the rook has to go to its target square.
  2. the alpha-castling (O-O-O, White's left side): like in FRC the king will be placed two rows distant from the border (here c-file) and the rook at the next inner neighboured square.
  3. the omega-castling (O-O, White's right side): like in FRC the king will be placed one row distant from the border (here i-file) and the rook at the next inner neighboured square.
d) performing castlings: within a GUI try to move the king upon the related rook or at least two squares into that direction; manually:
  1. move the king outside of the board
  2. move the rook to its end position (if need be)
  3. move the king to his end position
e) extended FEN encoding:
  1. the extended X-FEN could be used as a base
  2. 'a'/'A' are used to identify archbishops
  3. 'c'/'C' are used to identify chancellors
  4. '9' is used to mark nine empty squares
  5. "10" is used to encode ten empty squares
  6. if a castling enabled rook is not the most outer one at that side, the letter of his file has to be placed immediately following his castling marker symbol, where 'q'/'Q' are used for the alpha-, 'k'/'K' for omega-side.
f) engine notation rules for castling moves: According to UCI convention the castling moves should be written by using both coordinates (source and target field) of the involved king. But there are castlings, where the king does only one or none simple step. In that cases the castling should be distinguishable by appending a 'k', like already practized in promotion moves to make them unique. Overmore an engine should accept O-O or O-O-O (no zeroes), but only use them, when the GUI would demand for such a less precise notation.

g) comments and examples:

Reinhard Scharnagl.

Webpage created: February 24, 2005.
Webpage updated: October 6, 2018 by Greg Strong.
Written by Reinhard Scharnagl.