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Fairy chess and game depth
Jay Maron


History

Chaturanga, India, 600 AD
Courier chess, Europe, 1200 AD
Xianqi, China, 600 AD
Shogi,3 Japan, 1200 AD
Chu shogi, 1300 AD

Chess started in India as "chaturanga" around year 600 and spread to Asia as xianqi.

Chess appeared in Europe as courier chess in 1200, which added the bishop. In around 1500, the queen was added and this finalized the rules of modern chess. The queen variation was called "Mad-queen chess", and the existence of the queen expanded the power of pawn promotion.

Shogi emerged in Japan in 1200 and added many new pieces. Dai shogi emerged in 1230 and added even more pieces. "Dai" means "large". A shogi board is 9x9 and a dai shogi board is 15x15. Fairy shogi was a fad.

The pieces of shogi and xianqi have the same rule for motion and capture. The chess pawn is a rare piece with different rules. Fairy chess has many pieces with different rules for motion and capture.


Game depth

A goal for game design is depth, which can be defined as the difference between the world champion and an average human, measured by Elo ratings. The computer world champion can also be included.

Go and shogi have big depth. Chess has poor depth.

Go
Checkers
Chinese checkers
Backgammon

Elo ratings:

            Human  Computer  Top-tier  Average  #1024   #128    #1   Computer   Infinite  Year that computer  #1 human
            depth   depth     depth     human   human   human  human            computer  beat the #1 human   at the time

Go             3262   >5400     514       600    2400    3348   3862    5400      >6000       2016            Lee Sedol
Shogi          2200   >5000     700       600            1900   2800    4800      >5600       2013            Shinichi Sato
Xianqi         1983             386       800            2397   2783
Chess          1631   >2800     211      1200    2453    2620   2831    3642      >4000       1997            Gary Kasparov
Checkers       1240    1600     208      1200    2000    2232   2440    2814       2814       1995            Don Lafferty     Solved in 2007
Tic Tac Toe       0       0       0         0       0       0      0       0          0
Rock paper scissors  0    0       0         0       0       0      0       0          0
Billiards                       438                      2375   2813
Soccer         2600
Tennis         2400
Golf           2000
College bball                   514                      1387   1901

"Human depth" is the difference between the world champion and an average player.
"Computer depth" is the difference between an infinite computer and an average player.
"Top-tier depth" is the difference between the human #1 and the human #128.
An Elo ratings difference of 200 corresponds to a 3/4 probability for the stronger player winning.


Naturalness and Doom chess

Rules should be simple. Soccer rules are simple and football rules are complex.

Rules should yield a game with big depth, where depth is the difference between the world champion and an average player.

Doom chess has flexible rules. There are default rules and players may change them by gentleman's agreement. The default rules can be different for each tournament. Elements of Doom chess include:

There is a "draft", with a roster of pieces to choose from. Each piece has a value, and there is a value cap.

There is a "huddle". Each player decides his opening formation in secret.

The game ends when capture become impossible. The remaining pieces are totalled by points and the player with the most points wins.

The king is not sudden-death. Non-royal. It's okay for the king to be captured.

The game has blockers, which can't capture and can't be captured.

Balls can be added, which can be carried and passed. Each piece has a rule for passing and receiving. Yardage gains are part of the score function.


Naturalness of pieces

Most pieces should be full-directional. They should be able to move forward, backward, and to both sides. Furthermore, most pieces should be symmetric, where motion directions are symmetric and capture directions are symmetric.

A piece has a rule for motion, a rule for capture, and it can have special powers. Many combinations are possible. Doom chess chooses the most natural pieces.

Define "pure" to be a symmetric piece that has the same rule for motion and capture. They can be represented by 1 point on the chart.

Define "divergent" to be a symmetric piece with different rules for motion and capture. It can be represented by 2 points on the chart.


Classifying pieces

There are many versions of fairy shogi, and they collectively have most of the symmetric pieces. The chart shows the pieces of fairy shogi. Shogi uses the symmetry between rookwise and bishopwise motion.

The chart shows fairy chess space, where the X axis is rookwise range, the Y axis is bishopwise range, and the Z axis is knightwise range. The chart shows the Z=0 plane. A knight is {X,Y,Z} = {0,0,1}. An archknight has twice the range of a knight and is at {0,0,2}.

A blocker has a capture range of zero. This weakness is balanced by making it uncapturable.

Go uses a zero piece that doesn't move.

Most of the natural symmetric pieces are in the Z=0 plane. The Z=1 plane has all fusions of Z=0 pieces with a knight.

More dimensions exist, such as the camel leaper (3,1) and zebra leaper (3,2).


Roster of pieces

                  Move    Capture   Value   Armor   # for Doom   Features
                                                      chess

King                 *1        *1      4       0        1
Archking             *2        *2      6       0        1
Queen                *7        *7      9       0

Knight               ~         ~       3       0        2

Rook                 +7        +7      5       0        1
Rook3 (Wolf)         +3        +3      3.5     0        1
Rook2 (Dog)          +2        +2      2.5     0        1
Rook1 (Wazir)        +1        +1      1.5     0        1
Wazer                +1        x1      1.5     0        1
Puppy                +2        +1      2       0
Antipuppy            +1        +2      2       0

Bishop               x7        x7      3.5     0        2
Bishop3 (Lynx)       x3        x3      2.5     0
Bishop2 (Cat)        x2        x2      2       0
Bishop1 (Ferz)       x1        x1      1.5     0        2
Farz                 x1        +1      1.5     0
Kitten               x2        x1      1.75    0
Antikitten           x1        x2      1.75    0

Bishop3+ (Lynx+)     x3 or +1  x3      3       0
Bishop2+ (Cat+)      x2 or +1  x2      2.5     0        1
Bishop1+ (Ferz+)     x1 or +1  x1      1.75    0

Fullback             *1        +1      1.5     1

Blocker, king        *1        Unable  1       2
Blocker, queen       *7        Unable  2       2
Blocker, rook        +7        Unable  1       2        1
Blocker, bishop+     x7 or +1  Unable  1       2        1
Blocker, knight      ~         Unable  1       2        1

Joker                +1        +1      2                    Starts as a wazir. Can use its move to transform to any of {wazir, wazer, ferz, farz}
Forcer               +1        Unable  2                    Exerts a kingwise force on a piece in rook range. The piece can be friend or foe
Bomb                 +1        Unable  2                    If detonated, destroys itself and all pieces within a radius of 1, kingwise. Friend and foe pieces are destroyed.
Mortar               +1        +2      2                    Doesn't move when capturing

Diagonal pieces come in pairs, one light and one dark.

Numbers indicate range. Symbols for motion directions:

+    Rook
x    Bishop
*    King
~    Knight
|    Forward or backward
-    Right or left
^    Forward
v    Backward
d    Diagonally forward, either to the left or right, like a pawn capturing
e    The range is exact. No more, no less. The piece can leap.

"Armor" is the number of hits a piece can take without being captured.

After the forcer has forced a piece, the forced piece may not return to its previous square on the next move.

The roster has pieces from the rook-bishop chart. More pieces from the chart are possible, such as the fox and lion.

The names of fairy chess pieces are in a state of chaos and we ditch them. Mammals with short names are tapped, such as the dog, cat, wolf, lynx, fox, and lion.


Strength
The classical chess back row is strong pieces. The "nobility". Natural additions to the nobility are the archking, archbishop, and archrook.

Weak pieces are "serfs", such as the wazir, wazer, and ferz.

"Cantor pieces" are intermediate in strength between serfs and nobility, such as the dog and cat.

Doom chess avoids excessively strong pieces. Queens are so strong that it's rare for there to be an odd number of queens on the board. Even a queen with range 3 is excessively strong. An archking is a queen with range 2, slightly stronger than a rook.

Excessively strong pieces diminish the importance of lesser pieces. They're fork monsters. Don't have a piece that combines the moves of a knight and another piece. Also avoid the knightrider, a knight with extended range. That being said, have such pieces available in case players choose them by gentleman's agreement.

If a piece has a superstrong ability, give it a weakness for balance.

The cat+ is a compromise. It's a bishop with reduced range in exchange for the ability to move one square rookwise, noncapture.

You want to encourage exchanges between different kinds of pieces, and having pieces with a range of strengths helps.

The strength of a piece tends to be reflected by how often it's moved. Computers can do simulations and calculate this.


Direction diversity

Design pieces that synergize with other pieces. A good team is {rook, bishop, knight} for their diverse directions of motion, and it gives them forking power. A queen adds further diversity.

Direction diversity is possible because the board is Cartesian. A hexagonal board can't do this.


Board coverage

Bishopwise pieces cover only half the board. This can be mitigated by adding pieces like the cat+, which moves and captures like a cat and also moves like a wazir non-capture. It can also be mitigated by having several bishopwise pieces on each color. For example, have 2 each of ferz, cat, and bishop. Diagonal pieces should come in pairs, one light and one dark. Doom chess uses both of these measures.

A good team is {light bishop, dark bishop, archcat}, because you can lose one of them and still have full board coverage.

Pawns are poor team players. It's hard to make good pawn structure, and if a pawn captures, it often disrupts the structure.


Tribes

Define tribes by motion type. Rook, bishop, king, knight, bishop+. Each member of the tribe can have any range.

The bishop tribe has 2 subtribes, light and dark. Doom chess uses bishopwise pieces in pairs, one light and one dark.

Doom chess has 2 pieces from the king tribe and 2 pieces from the knight tribe. It has only one rook7 because rooks have full board coverage. Having only one rook7 makes room for more rookwise pieces and more diversity.


Diversity, attack asymmetry, and forking power

"Attack asymmetry" is where a piece can attack another piece and the other piece can't attack back. This is part of the magic of chess and it leads to forking opportunities. "Fairy space" is the structure of attack diversity. Diversity can come from many sources:

*) Direction diversity, for example the {rook,bishop,knight} set. The queen adds further diversity by combining directions.

*) Range for capture.

*) Range for motion. Fast pieces outmaneuver slow pieces.

*) Divergent pieces, with different rules for motion and capture. For example, the wazer, which moves like a wazir and captures like a ferz.

*) Rank

*) Flavor. For example, rock paper scissors.

*) Motion that depends on terrain.

*) Pieces that capture without moving, like a mortar.

*) Creation. The ability to create a new piece and put it on the board.

*) 3D motion.


Piece strength

If two pieces are combined, the strength of the fusion tends to be equal to the sum of the parts, plus a small bit. For example, a queen is stronger than a rook + bishop.

For pieces with large range, rookwise range is stronger than bishopwise range.

For pieces with small range, rookwise range is weaker than bishopwise range. A wazir is weaker than a ferz because it needs 2 moves to make 1 ferz move.

The strength of a piece tends to scale with the number of squares it can reach in a move. This often depends on board location. Board coverage also matters. Bishopwize pieces cover only half the board.

Define a function for the strength of a piece as Sxyz, which can be measured with simulations. x is rookwise range, y is bishopwise range, and z is knightwise range.

Define a difference function Dxyz

Sxyz = Sx0z + S0yz + Dxyz

Define a knight function Kxy

Kxy = Sxy1 - Sxy0

A piece that moves rookwise with range i and captures rookwise with range j has strength Rij.

A piece that moves bishopwise with range i and captures bishopwise with range j has strength Bij.

There are two more functions for pieces with mixed ranges for motion and capture.

The precise strengths of the wazir and ferz are fundamental parameters to measure.

It's rare for a bishop to have a chance to move with range 7. It's from corner to corner, and bishops shouldn't be in corners. A bishop with range 5 is worth almost as much as a bishop with range 7.

The following table gives an estimate of value as a function of range.

Range   Rook   Bishop  King   Knight  Bishop+  Camel  Zebra  Blocker  Blocker  Blocker  Blocker
                                                              Rook    Bishop    King    Knight

 1      1.5    1.5    3.5     3      2.0      2.5    2.5        .5      .5       1        1
 2      2.5    2.0    6       5.5    3.0      5      5          .7      .7       1.25     1.5
 3      3.5    2.5    7.5     8      3.5      -      -          .8      .8       1.5      1.75
 4      4.0    3.0    8       -      3.75     -      -          .9      .9       1.65     -
 5      4.5    3.25   8.5     -      4.0      -      -         1.0      .95      1.8      -
 6      4.75   3.5    9       -      4.25     -      -         1.1      .8       1.9      -
 7      5      3.5    9.5     -      4.25     -      -         1.2     1         2        -

Draft chess

Draft chess has a roster of pieces to choose from. Each piece has a price. Each player has a budget for buying pieces, like a salary cap.

Each player drafts in secret and then decides an initial formation in secret.

Players may add pieces to the roster by gentleman's agreement, and they can change the piece values.


Triangle pieces
An example of a triangle piece is a piece that moves forward rookwise and backward bishopwise. Triangles have 8 possible orientations.

A triangle piece is full-directional and has full-board coverage.

Triangle pieces aren't symmetric. They can be made symmetric by giving them the ability to transform to a different kind of triangle. A transforming triangle is a "turret".


Discontinuity of goals

Avoid discontinuity of goals. For example, a sudden-death king is a discontinuity in that the value of a king is infinite compared to other pieces. It's an obstacle to balance among pieces. It diminishes the king's options and is an obstacle to complexity.

Chess pawns are a discontinuity because they're low strength but can become queens. Also, the fact that they're one-way diminishes complexity.

Castling is an awkward rule. Ditch it. Also ditch en passant.


Offense

Offense is hard to generate. Blockers and bombs help.

In classical chess, it's hard to generate offense with pawns because it's hard to pass a defensive line of opposing pawns.

Pawn battles are often boring because all pawns have the same powers.

You want to get your pieces into enemy territory, but there are hazards. The invading pieces should be weak pieces. They should have the ability to capture backwards and support the next wave of attackers.


Board coverage

Avoid leapers other than the knight. The {2,0} leaper covers only 1/4 of the board and the {2,2} leaper covers only 1/8. The {3,1} and {3,2} leapers cover the full board. They're unnatural but some players like them.


Draws

Design rules that discourage draws.

Classical chess has a rule that the game is a draw if any possible move results in self checkmate. Ditch this rule.

Draws can be lessened by disallowing repeat positions.

Grandmaster-level games draw around half the time. Among non-draws, white wins around 3/5 of the time. The higher the level of play, the more frequent the draws. Blitz has a lower fraction of draws than classical chess.

The fact that chess is prone to draws decreases game depth.

Find ways to equalize black and white. For example, declare that if the piece count at the end of the game is equal, then black wins. Clock times can also be unequal between players. This is analogous to "komi" in the game of go.

Draws can be lessened by eliminating the sudden-death of kings, and by tallying piece strengths at the end of the game.


Rank

Pieces can have rank, where you can only capture a piece with equal or lower rank.


Flavor
The game of rock-paper-scissors has pieces with multiple flavors. No flavor is strongest. This opens forking power. For example, a piece with "rockness" can capture a piece with "scissorsness" but not with "rockness" or "paperness".

It can be expanded to 5 pieces by adding a spock and a lizard. It can be expanded to any set of pieces with odd number.


Powers

Some of the fundamental powers are:

Motion
Capture
Transform      Can transform to a different kind of piece
Rank
Armor          The ability to take multiple hits before being captured.
Damage         The ability to subtract more than one armor point in a hit
Healing        Add hit points to pieces
Mortar         Can capture without having to move
Force          Exerts a force on a piece within forcing range. The piece has a pattern for the force it can exert
Stun           Stuns a piece for N moves
Bomb           Explodes and destroys all pieces within bomb range. The bomb is also destroyed
Banish         Send to a penalty box for N moves
Ambassador     Protects nearby friendly pieces
Ball passing
Ball receiving
Ball interception
Terrain-based powers
Ability to change board terrain
Ability to change board connectivity or create new space
Coordinated moves between pieces, like castling
Piece drops
Simultaneous moves, where both players move simultaneously

A forcer exerts a force on other pieces. A forcer has a range of motion, a range for exerting force, and a range for the impact of the force. All ranges are independent and any combination can be chosen. A forcer can force its own pieces or an opponent's. A piece that was forced must wait at least 1 move to return to its former square. Repeat positions are disallowed, like in the game of go.

A bomb can't capture. It can detonate, whereupon it destroys itself and all pieces within a radius of 1, kingwise. This includes friendly pieces.

A stunner stuns a piece within stun range for N moves. A stunned piece may not move or capture.

Some games have terrain, such as inaccessible squares. Xianqi is an example. One can give pieces powers or weaknesses that depend on terrain. A power can be to change terrain.


Armor points

Armor points is the ability to take hits without being capture. Each hit subtracts an armor point.

Most pieces have 0 armor points, in the sense that they can be captured in one turn.

A piece that's uncapturable has infitinte armor points. A blocker.


Terrain and 3D

Give squares the ability for multiple occupancy.

Add a 3rd dimension.

The properties of a piece can depend on terrain.

Pieces can have the power to change terrain.


Football chess

Each side has a ball, which is carried by a piece. A piece may pass the ball to another piece that's within its passing range, and if the ball passes through the receiver's range.

Each piece has a rule for passing, receiving, and interception. Some pieces may be designated as ineligible to carry the ball.

Each side starts with a ball on their back row, and the goal is to move your ball as far forward as possible before the ball-carrier is captured (tackled). One point for each row forward. You must also defend against the enemy ball.

Alternately, the score can be based on the number of rows gained without being captured. If a piece advances and isn't captured on the next move, it gets credit for forward progress.

Give credit for forward progress. The score is the furthest the ball advanced during the game.

Each side can have multiple balls, and the total score is the total rows gained.

One can specify how many balls a piece may carry. The number could be zero. An ineligible receiver.

One can specify a move limit at which time the game ends and points are tallied. This promotes risk.

One can include columns in the scoring function. For example, reward being close to the center, like rugby.

One can include a goal zone. There can potentially be space behind the goal zone, like for hockey.

Have the option for arbitrary geometry and terrain. A piece's powers can depend on terrain.

Pieces can have more than one armor point. For example, it may take more than one tackle to capture a ball carrier.

If the score is tied at the end of the game, the winner is the first to achieve the score. Or, you could have overtime. Keep moving until one side has a better score.


Football chess roster


                        Move  Capture  Pass  Receive  Web  Armor  Value

King1     King            *1     *1     *1      U                  3.5
King2     Archking        *2     *2     *1      U                  6
King3                     *3     *3     *1      U                  7.5
King7     Queen           *7     *7     *1      U                  9.5

Rook1     Wazir           +1     +1     *1      U                  1.5
Rook2     Dog             +2     +2     *1      U                  2.5
Rook3     Wolf            +3     +3     *1      U                  3.5
Rook7     Rook            +7     +7     *1      U                  5

Bishop1   Ferz            x1     x1     *1      U                  1.5
Bishop2   Cat             x2     x2     *1      U                  2.0
Bishop3   Lynx            x3     x3     *1      U                  2.5
Bishop7   Bishop          x7     x7     *1      U                  3.5

Knight1   Knight          ~1     ~1     *1      U                  3
Knight2   Archknight      ~2     ~2     *1      U                  6
Knight3   Knightrider     ~3     ~3     *1      U                  9

Bishop1+  Ferz+           x1,+1  x1     *1      U                  2
Bishop2+  Cat+            x2,+1  x2     *1      U                  3
Bishop3+  Lynx+           x3,+1  x3     *1      U                  4

Blocker                   +7                                 2     1.5     Ineligible to carry the ball
Running back              *7     +1     *1      U                  3
Fullback                  *2     +1     *1      U            1     3
Quarterback, slow         +1     +1     *7      U                  3
Quarterback, fast         *2     +1     *2      U                  3
Midfielder                +1     +1     *2      U     +1           3
Goalie                    *1     +1     *1      U     *1           3
Receiver                  *2     +1     *1      U     +1           3
Enforcer                  +1     *1     *1      U            1     3
A blank entry means that the piece doesn't have the feature.

"U" means universal receiver. Can catch the ball from any direction.

"Armor" is the number of hits that a piece can survive without being captured.

"Web" means that the piece can catch or block balls that are within web range.


Rugby chess

If a piece with a ball is tackled, the ball goes to the tackling team.

When the move count expires, the positions of the balls are measured.


Computers

A computer can vary the choice of pieces and formation and find choices with big depth.

The game of go hinges heavily on experience. A general property of a game is the degree to which experience matters, and it varies between games. It's a matter of taste. Some like games that emphasize experience and some like games that don't. The rules of Doom chess can be steered to either emphasize or de-emphasize experience.

A goal is to diminish the importance of computers. Imagine a tournament where players are sequestered so that they can't communicate with computers.

A game can be designed for a team of humans and computers. For example, a game can have goals for which there is no engine.

Wise tournament structure can promote drama and generate ticket revenue. Blitz games are exciting.

A computer can simulate a game and calculate piece strengths.

A computer can evaluate each piece's fraction of the total moves, and this tends to be proportional to the strength of a piece.


Game depth

Let T be the time given to a computer per move, and S(T) be the ratings strength.

S will have an approximate form S ~ D(T) ln(T), where D(T) is game depth. D will be a weak function of T.

Rosters of pieces can be varied to study the effect on D, and strategic rosters can be identified to maximize D.

Let V be the value of a piece and let Vteam be the sum of piece values. Doom chess is a roster that maximizes D/Vteam.


Clocks

Give each player a clock so that they can put it where they please. Connect them wirelessly. Such clocks help team chess.

An electronic board can sense piece movement, making clocks unnecessary. This increases the watchability of blitz chess.


Laskers

Emanuel Lasker (1868-1941)
Emanuel Lasker and Berthold Lasker (1860-1928)
Edward Lasker (1885-1981)
David Hilbert (1862-1943)

Emanuel Lasker, Berthold Lasker, and Edward Lasker are all chess grandmasters and mathematicians, and they're all related and friends. They worked together to promote go and fairy chess.

Emanuel Lasker was the chess world champion and his mathematics PhD advisor was David Hilbert.

Edward Lasker: "While the Baroque rules of Chess could only have been created by humans, the rules of Go are so elegant, organic, and rigorously logical that if intelligent life forms exist elsewhere in the universe, they almost certainly play Go."


Triangle chess

Triangle chess is a generalization of square chess. It has the pieces of square chess, plus triangle pieces.

Triangle chess adds new angles to square chess. Square chess has the angles of rook, bishop, and knight. Triangle chess adds angles for the badger and gopher.

Badger    Gopher    Trishop    Hawkeye    Wolverine
Badger    Gopher    Trishop    Hawkeye    Wolverine

A beaver is a trishop with half steps.

The elements of square chess are the rook, bishop, and knight. Molecules are sums of elements, such as

Queen = Rook + Bishop

The chart shows the elements of triangle chess. The molecules are:
Tring = Badger + Gopher
Packer = Badger + Trishop
Viking = Gopher + Trishop

The first two beaver ranges are equivalent to other pieces.
Beaver1 = Badger1
Beaver2 = Packer1

__________

Some triangle pieces are useful and some aren't.

A Badger1 is a subset of a Rook1. Ditch it.

A Badger2 is fundamentally different from square pieces and has full board coverage. Keep it.

Badgers with range larger than 2 are interesting. Use them. A Badger3 has 9 moves and isn't excessively powerful.

A Gopher1 covers only 1/4 of the board and has a poor turning radius. Ditch it.

A Gopher2 is fundamentally different from square pieces and has full board coverage. Keep it.

Gophers with range larger than 2 are interesting. Use them. A Gopher3 has 9 moves and isn't excessively powerful.

A trishop are similar to a bishop. Ditch it.

A Hawkeye1 is similar to a knight and more knightness is needed. It also has a 3-leap horizonal motion. It has 6 moves and is slightly weaker than a knight. Use it.

A Hawkeye2 is absurd. Ditch it.

A Wolverine1 is absurd. Ditch it.

A Tring1 is part rook and part knight. It has 6 moves. It's interesting because it's vulnerable to diagonal pieces. Keep it.

A Packer1 and Viking1 have 9 moves and are similar to a king. Ditch them.


Hex chess

Rook
Bishop
King
Queen
Knight
Pawn

A piece that moves like a bishop covers 1/3 of the board.

The chart shows pieces that are full-directional. More combinations are possible.


Standard variations

One can define a set of standard rulesets, which players can change by gentlemen's agreement. Playtesting will lead to a good list of standard rulesets.

A tournament can define a ruleset that's released when the tournament begins.

Rules can be designed that flummox AI. Make the rules hard to program.


Appendix

Dai shogi

King
Angry boar
Cat sword
Violent ox
Flying dragon
Lion

Queen
Rook
Bishop
Dragon king
Dragon horse

Drunk elephant
Gold general
Silver general
Copper general
Iron general
Stone general
ferocious leopard
Evil wolf
Go-beteen
Pawn

Flying stag
Vertical mover
Side mover
Flying ox
Free boar
White horse
Reverse chariot
Lance

Sea lion
Kirin
Phoenix
Forward knight
Soaring eagle
Horned falcon

Numbers indicte the approximate year that the game emerged.

Rookwise  Bishopwise  Modern  Chaturanga  Courier   Xianqi   Seven      Shogi        Dai shogi     Tai shogi     Ko shogi
 range      range     chess               chess              Kingdoms
                      1500    600         1200      600      1200       1200         1230          1400          1700

   1           1      King    Raja        King                          King         King          King          General
   7           7      Queen                                  General                 Queen         Queen         Millenary
   7           0      Rook    Ratha       Rook      Chariot  Chancellor Rook         Rook          Rook          Chariot
   0           7      Bishop              Bishop             Diplomat   Bishop       Bishop        Bishop        Elephant
   -           -      Knight  Ashva       Knight    Horse                                                        Cavalryman
   -           -                                                        Shogi knight Shogi knight  Shogi knight
   -           -      Pawn    Padati      Pawn
   -           -                                    Shogi pawn          Shogi pawn   Shogi pawn    Shogi pawn
   1           0                          Wazir     General  Sword                   Angry boar    Angry boar    Pawn
   0           1              Mantri      Ferz      Advisor  Dagger                  Cat sword     Cat sword     Longbow
   0           2e             Gaja        Alfil     Elephant
   2           0                                                                     Violent ox    Violent ox
   0           2                                                                     Flying dragon Flying dragon
   7           1                                                        Dragon king  Dragon king   Dragon king   Quartermaster
   1           7                                                        Dragon horse Dragon horse  Dragon horse  Centuria
   7           2                                                                                                 Tiger wing
   2           7                                                                                                 War hawk
   2           2                                                                                   Mastodon
   3           3                                                                                   Lion dog
   4           4                                             Archer
   5           5                                             Crossbowman
   5           0                                                                                                 Flag waver
   0           5
   5           2                                                                                   She-devil
   2           5                                                                                   Dove
   -           -                                                        Gold gen     Gold gen      Gold gen      Gold gen
   -           -                                                        Silver gen   Silver gen    Silver gen    Silver gen
   -           -                                                                     Copper gen    Copper gen    Copper gen

Boards

               Board   Piece types   Pieces   Year

Chaturanga        8x8       6         16      1200
Modern chess      8x8       6         16      1500
Carrera chess    10x8       8         20      1627
Courier chess    12x8      10         24      1200
Shogi             9x9       8         16      1200
Xianqi            9x10      7         16      1200
Dai shogi        15x15     29         65      1230
Dai dai shogi    17x17     64         96      1400
Ko shogi         19x19     34         90      1700
Tai shogi        25x25     93        177      1400
Taiyoku shogi    36x36    207        402      1550
Go               19x19      1        170      -500

Draws

Probabilities in percent:

                            White wins   Black wins   Draw   Fraction of white wins
                                                                among non-draws

Tournaments, 1851-1878             45.5    40.4      14.1           53.0
Tournaments, 1881-1914             36.9    31.4      31.8           54.0
Tournaments, 1919-1932             37.0    26.0      37.0           58.7
World championships, 2000-24       20.0     9.3      71.0           68.3
Chess engines, 2009                34.7    24.0      41.3           59.1
World Blitz Championships, 2009    39.0    34.6      26.4           53.0

Move frequency

For classical chess, the fraction of moves for an individual piece is:

    Fraction of moves   Total moves  Value  Fraction/value

Queen      .237         3.53           9       .026
Rook       .155         2.31           5       .031
King       .217         3.23           4       .054
Knight     .174         2.58           3       .058
Bishop     .151         2.25           3       .050
Pawn       .065          .97           1       .065

Total                  28.8

Capture frequency

A game has an optimal capture frequency. Too large or too small is bad for depth.

The modern capture frequency is 1/5, and in 1850 it was 1/4.

Master games tend to have a lower capture frequency than amateur games.

A game averages 16 captures upon conclusion.

          Final move   Capture frequency

Opening        16        1/3
Middle game    22        1/5
End game       32        1/7

Chess time control

        Initial time   Time added per move   Time per move
          minutes            seconds            seconds

Classical   90                30                165
Rapid       15                10                 32.5
Blitz        5                 3                 10.5
Bullet       1                 0                  1.5

"Time per move" assumes 40 moves for each player.


Variants

          Columns  Rows  Year     Pieces

Capablanca    10    8   ~1925     Rook+Knight    Bishop+Knight        Classical pieces
Shako         10    8             Elephant       Cannon               Classical pieces
Grand         10   10             Rook+Knight    Bishop+Knight        Classical pieces



Fairy chess pieces

Fairy chess names are in a state of chaos. These are the names.


Flavor

More options for flavor:


World rankings

Number of people in the top 20:

           Men   Women   Men U21   Women U21

India        4     4       6       4
USA          6             2       3
China        2     5               2
FIDE               2       2       1
France       2             1       1
Kazakhstan         1               3
Ukraine            3
Uzbekistan   1             1       1
Russia       1     1       1
Norway       1             1
Netherlands  1                     1
Switzerland        1               1
Azerbaijan   1             1
Turkey                     2
Hungary                            1
Bulgaria                           1
Slovenia     1 
Poland             1
Belgium                    1
Serbia             1
Mongolia                           1
Georgia            1
Belarus                    1
Iran                       1

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© Jason Maron, all rights reserved.

Data from Wikipedia unless otherwise specified.