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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 xiangqi.

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 xiangqi 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
Scrabble

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
Xiangqi        1983   >3200     386       800            2397   2783    3950      >4500      2006            Xu Yinchuan
Chess, men     1631   >2800     211      1200    2453    2620   2831    3642      >4000      1997            Gary Kasparov
Chess, women   1550             335      1100    2085    2315   2650              >4000      1993            Judit Polgar
Scrabble       1450   >1700               800                   2250    2500      >2500      2006            David Boys
Backgammon     1250   >2000              1500                   2750    3250      >3250      1979            Hans Berliner
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

Tennis, men                     600                      -600      0
Tennis, women                   500                      -500      0
Billiards                       438                      2375   2813
Golf           2000             120

Soccer         2600             850         0            1750   2600
College football                400                      -400      0
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.
For soccer, we use the English soccer league system.


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.


Classifying pieces

A piece has a rule for motion, a rule for capture, and it can have special powers. Many combinations are possible.

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.

There are many versions of fairy shogi, and they collectively have most of the symmetric pieces. Fairy 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}.

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).

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


Roster

Doom chess emphasizes pieces that are full-directional. Such pieces can move forward, backward, and to both sides. Furthermore, most pieces should be symmetric, where motion directions are symmetric and capture directions are symmetric.

A blank entry in the table indicates a value of 0.

                  Move    Capture   Value   Armor  Caliber  # for Doom   Features
                                                              chess

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

Knight (2,1)         ~         ~       3              1         2
Archknight (2,1)     ~2        ~2      6              1
Camel (3,1)        (3,1)     (3,1)     2.5            1
Zebra (3,1)        (3,2)     (3,2)     3              1

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

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

Bishop3+ (Lynx+)     x3 or +1  x3      3              1             Cardinal3
Bishop2+ (Cat+)      x2 or +1  x2      2.5            1         1   Cardinal3
Bishop1+ (Ferz+)     x1 or +1  x1      2              1             Cardinal3

Roship               +7        x7      5
Bishook+             x7 or +1  +7      4.5

Blocker, king        *1        Unable  1       2      0
Blocker, queen       *7        Unable  2       2      0
Blocker, rook        +7        Unable  1       2      0         1
Blocker, bishop+     x7 or +1  Unable  1       2      0         1
Blocker, knight      ~         Unable  1       2      0         1
Archbishop           x1 or ~   x1 or ~ 5              1
Honey badger         *1        +1      2       1      1
Bull (enforcer)      *1        +1      2              2
Stone                                   .5     1      0

Joker                +1        +1      2              1             Starts as a wazir. Can use its move to transform to any of {wazir, wazer, ferz, farz}
Forcer               +1        Unable  2              0             Exerts a kingwise force on a piece in rook range. The piece can be friend or foe
Bomb                 +1        Unable  2              1             If detonated, destroys itself and all pieces within a radius of 1, kingwise. Friend and foe pieces are destroyed.
Mortar               +1        +2      2              1             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.

"Caliber" is the number of armor points subtracted by a hit.

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. The table lists the most natural combinations, but any combination is possible.

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.

The camel and zebra add forking powor.

Mixed pieces like the roship and bishook add forking power.

A Cartesian board enables big directional diversity, and a hex board has less diversity.


Board coverage

Diagonal pieces cover only half the board. This can be mitigated by adding pieces like the bishop+, which moves and captures like a bishop 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 bishop1, bishop2, and bishop7. 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, bishop+}, because you can lose one of them and still have full board coverage.

The camel is colorbound and the zebra isn't.

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

Most leapers have poor board coverage. Board coverage for leapers:

Vertical

   5                          1/16
   4                    1/16   1                                                     Commuter
   3              9/64   1    1/2                                         Tripper    Antelope
   2        1/4    1    1/4    1                                 Alfil    Zebra      Stag
   1  1/2    1    1/2    1    1/2                         Ferz   Knight   Camel      Giraffe
   0   1    1/4   9/64  1/16  1/16  1/16            Zero  Wazir  Dabbaba  Threeleap  Fourleap

       1     2     3     4     5     6   Horizontal   0     1       2         3         4

An amphibian is (1,1)+(3,0) and it has full board coverage.


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        2      2.5        .5      .5       1        1
 2      2.5    2.0    6       5.5    3        3      4          .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        Move to a square and capture the piece in it
Transform      Can transform to a different kind of piece
Armor          The ability to take multiple hits before being captured.
Caliber        The ability to subtract more than one armor point in a hit
Armorer        Add armor to pieces
Rank           A capturing piece must be >= the rank of the captured piece
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
Repel          Exerts a repulsion on all pieces within repulsion range.
               The opposing player must then  move a piece within the repulsion zone out of the repulsion zone.
               It is allowed to capture the repeller.
Bomb           Explodes and destroys all pieces within bomb range. The bomb is also destroyed
xert
Banish         Send a piece 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. Xiangqi 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.


Chess with balls

A ball can be on the ground or it can be carried by a piece. A piece can pick up and put down a ball.

A piece has a passing pattern and a receiving pattern. A piece may pass the ball to another piece that's within its passing pattern, and if the ball passes through the receiver's receiving pattern.

Some pieces have an interception pattern or a goalie pattern.

A piece has a pattern for kicking.

Each side starts with balls 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.

The game can start with balls on the ground.

Some pieces may have the power of inducing a fumble, or to strip a ball.

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 offense with the ball.

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.


Yardage chess roster


                        Move  Capture  Pass  Receive  Web  Armor  Caliber  Value

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

Rook1     Wazir           +1     +1     *1      U                  1       1.5
Rook1H    Wazir, heavy    +1     +1     *1      U            1     2       2.0
Rook2     Dog             +2     +2     *1      U                  1       2.5
Rook3     Wolf            +3     +3     *1      U                  1       3.5
Rook7     Rook            +7     +7     *1      U                  1       5

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

Knight1   Knight          ~1     ~1     *1      U                  1       3
Knight2   Archknight      ~2     ~2     *1      U                  1       6
Knight3   Knightrider     ~3     ~3     *1      U                  1       8

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

Blocker, rook             +3                                 1             1.5  Ineligible to carry a ball
Blocker, rook, heavy      +2                                 2             1.5  Ineligible to carry a ball
Blocker, bishop           x3                                 1             1.5  Ineligible to carry a ball
Blocker, bishop, heavy    x2                                 2             1.5  Ineligible to carry a ball
Blocker, knight           ~1                                 1             1.5  Ineligible to carry a ball
Blocker, knight, heavy    ~1                                 2             2.0  Ineligible to carry a ball
Running back              *3     +1     *1      U                  1       3
Fullback                  *2     +1     *1      U            1     1       3
Quarterback, slow         +1     +1     *3      U                  1       3
Quarterback, fast         *2     +1     *2      U                  1       3
Midfielder                +1     +1     *2      U     +1           1       3
Goalie                    *1     +1     *1      U     *1           1       3
Receiver                  *2     +1     *1      U     +1           1       3
Enforcer                  +2     *1     *1      U            1     1       3
Enforcer, high caliber    +2                                 1     2       1.5  Ineligible to carry a ball

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.

"Caliber" is the amount of damage inflicted in a hit. The amount of armor subtracted. Most pieces have a caliber of "1".


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.


Timeouts

Blitz chess could add timeouts. For example, give each player 3 timeouts of 30 seconds each. It gives the crowd a chance to catch up with the game.

In general, there can be a function that converts the physical time taken for a move to a time charged on the clock, and the function can be non-linear.


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-between
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

Distribution of movement range

Rooks are more likely to move long-range than queens or bishops. Queens and bishops are have similar probabilities for long-range moves. The fraction of moves of a given range is:

Range   Rook   Bishop  Queen    Queen       Queen
                       total  rook-wise  bishop-wise

  1     .25    .32     .30      .19       .11
  2     .20    .24     .20      .11       .09
  3     .18    .18     .15      .08       .07
  4     .15    .12     .11      .06       .05
  5     .10    .07     .08      .04       .04
  6     .07    .04     .06      .03       .03
  7     .05    .03     .04      .02       .02

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.

          Move range   Capture frequency

Opening       1-16        1/3
Middle game  17-22        1/5
End game     23-32        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

Example game for fairy chess


Elo ratings on boardgamearena.com

Define "depth" as the difference in rank between the #4 and the #64 ranked players, divided by 4.

Elo rating by rank:


                   Depth  Matches   #1    #2    #4    #8    #16   #32   #64  #128  #256 #512 #1024 #2048 #3072 Comp-   Strat-  Luck  Commun-   # of rated
                          million                                                                              plexity  egy          ication    players

Logic              ~130      .58   2319  2173  2103  1872  1752  1660  1537                                      1      5      1      0       72    Cards. Speed
Shogi        World  129            2800                                      1900
Spot It!           ~100      .89   2149  2064  1962  1893  1734  1648  1520                                      1      1      0      4       71    Pattern recognition speed
Hive            BS ~100            2098  1928  1736  1548  1504  1436                                                                         49    Hex tiles
Hand and Foot        87      .53   1650  1643  1626  1602  1588  1570  1539  1493                                3      3      3      1      178
Hive                ~80     1.04   1797  1774  1700  1627  1538                                                  3      5      0      0       24    No board. Hex tiles
Ticket to Ride: Map  76      .23   2115  2094  1933  1823  1775  1706  1627  1582  1485                             Not rated                344
Tennis, Men   World  74            2297  2272  2068  1980  1927  1850  1772  1667  1513                                                      515
Railroad Inc         73     2.6    2016  1984  1972  1928  1858  1768  1679  1573                                2      3      3      0      185    Deep Blue Edition
Distilled            70      .17   1949  1860  1808  1716  1646  1570  1505                                      3      4      2      1       82    Cards and coins
Sushi Go             69     3.8    2046  2018  1936  1860  1813  1758  1661  1603                                2      3      2      2      251
Welcome Perfect Home 67     2.8    2083  2036  2024  1940  1904  1848  1755  1683  1555                          2      4      1      1      325 
Splendor             65     9.9    2223  2220  2135  2109  2004  1955  1876  1798  1716  1634  1512              3      3      2      2     1288    Cards and coins
Castles of Burgundy  63     3.9    2041  2024  2018  1928  1878  1823  1765  1711  1640  1526                    3      4      2      1     1222    Hex board size 4. Tokens and dice. No battle
Patchwork            62     3.0    2047  2025  2002  1932  1904  1838  1752  1685  1447                          3      3      3      3      256    Square board 9x9, tokens
Seasons              62    10.2    1928  1907  1870  1825  1778  1667  1621  1530                                3      4      2      1      239
Feast of Odin        62      .45   1965  1965  1857  1831  1776  1647  1528                                      5      4      1      1       84    Economic
Go            World  59            3852  3733  3692  3664  3622  3553  3457  3359  3230  3006                                                893
Ticket Ride: Europe  58     2.7    2050  2043  1998  1980  1930  1852  1765  1696  1630  1543                    2      3      3      2      812
Jaipur               58     2.9    1903  1899  1849  1813  1759  1675  1591                                      2      2      2      0       77
Ticket to Ride       54    15.9    2157  2103  2082  2060  2011  1948  1867  1810  1735  1669  1595  1475        2      3      3      2     2678    Topology
Bubblee Pop          52     2.3    1869  1866  1817  1754  1720  1665  1610  1520                                1      2      3      0      187
Through the Ages     50     1.14   2014  1916  1887  1822  1744  1667  1503                                      4.42   4      2      3       72    Cards
Kingdom Builder      50     2.8    1917  1902  1854  1801  1746  1709  1654  1604  1541                          2      3      2      3      421
Stone Age            50     5.7    1998  1918  1891  1870  1820  1760  1691  1624  1524                          3      3      3      3      349
Gaia Project         50      .43   1870  1753  1736  1651  1590  1557                                            4.37   4      1      2       55    Hex board tokens, money, battle
The Vale of Eternity 48      .27   1910  1891  1764  1740  1680  1632  1571  1507                                3      4      2      2      188
Kingdomino           47     6.8    1991  1988  1928  1902  1846  1797  1740  1674  1596                          1      3      4      1      385
Puerto Rico          47     2.8    1998  1765  1743  1731  1699  1628  1556                                      4      4      1      1      101
Chess, Blitz  World  45            2869  2838  2796  2765  2722  2676  2616  2554  2479  2391  2289  2174  2105                            46000
7 Wonders Duel       45    13.1    1974  1948  1923  1887  1838  1790  1743  1708  1659  1609  1522              3      4      2      3     1492
Potion Explosion     44     3.0    1881  1859  1828  1792  1760  1704  1654  1599  1530                          1      2      3      1      354
Terraforming Mars    43     4.2    2113  2053  2040  1994  1958  1916  1867  1821  1761  1675  1544              4      4      3      1     1347
Chakra               41     4.0    1922  1842  1827  1808  1732  1702  1663  1616  1546                          2      4      2      2      514 
Space Base           39     3.6    1917  1916  1862  1835  1773  1737  1706  1656  1614  1559  1458              2      2      3      1     1269
Captain Flip         39     2.2    1857  1843  1817  1760  1722  1696  1660  1631  1593  1546  1428              2      2      4      0     1095
Agricola             39     1.68   1828  1812  1800  1761  1732  1690  1643  1587                                3      5      1      2      233    Simple board. Cards
Race for the Galaxy  38    13.8    1889  1853  1829  1815  1775  1720  1679  1613  1531                          4      3      2      1      444    Cards
CuBirds              38     7.4    1829  1828  1795  1751  1712  1673  1645  1611  1572  1503                    1      3      3      1      706
Ark Nova             37    11.0    2157  2150  2077  2056  2004  1969  1930  1885  1828  1769  1688  1585  1436  3.74   5      1      2     3298    Board, tokens, and cards
7 Wonders            37    11.8    1872  1869  1861  1830  1799  1753  1712  1679  1638  1593  1514              3      3      2      2     1305    Cards
Xiangqi       World  37            2783  2754  2624  2610  2577  2524  2476  2397                                                            206    Square board
Carcassonne          36     9.5    2045  2022  1999  1969  1936  1896  1853  1792  1734  1647  1509              1      3      3      3     1365
Yahtzee              36    10.9    1943  1918  1864  1842  1792  1758  1720  1679  1631  1530                    0      1      5      0      678    Dice
Lost Cities          34     5.0    1830  1780  1759  1731  1699  1659  1622  1589  1552  1742                    1      4      2      2      617
Backgammon           34     5.9    1836  1830  1775  1737  1717  1674  1639  1591  1504                          1      2      4      0      341    Tokens and dice
Chess, Class. World  34            2840  2810  2780  2754  2731  2695  2642  2591  2524  2446  2369  2279  2219  3.64   5      0      0    95000
Chess, Rapid  World  31            2832  2755  2741  2727  2694  2663  2616  2574  2500  2425  2340  2237  2174                            65000
Chess engines World  31            3651  3649  3628  3626  3617  3584  3503  3320  2917  2228                                                674
Wingspan             31     8.7    1903  1893  1866  1822  1793  1772  1743  1707  1671  1624  1563  1342        3      3      3      3     2037
Lucky Numbers        26    11.7    1797  1785  1768  1739  1728  1694  1664  1641  1611  1578  1522              1      2      4      1     1554
Hearts               25     2.54   1765  1762  1733  1718  1688  1671  1633  1609  1570  1530  1413              2      2      3      1     1078
Take 5               23     8.3    1762  1754  1737  1706  1691  1669  1644  1620  1594  1561  1492              1      1      4      3     1131    Cards
Azul                 22    12.5    2224  2201  2120  2096  2061  1994  1931  1874  1813  1748  1676  1582  1499  1      3      3      3     4140    Tokens and patterns
Can't Stop           21    15.2    1775  1775  1746  1725  1698  1675  1663  1642  1615  1588  1547  1455        0      1      5      0     2307    Tokens and dice
7 Wonders: Architect 21     4.1    1753  1713  1703  1682  1664  1640  1619  1596  1563  1515                    1      3      1      1      818
Catan                20     7.4    1812  1773  1761  1747  1720  1698  1680  1657  1630  1603  1569  1518  1449  2      3      3      4     3379    Hex board and tokens
Texas Hold'em        20      .32   1723  1698  1694  1673  1657  1636  1616  1593  1568  1528                    3      4      2      0      870    Cards and bluffing
King of Tokyo        20     2.8    1765  1685  1679  1658  1631  1600  1568  1529                                2      2      3      3      492
Solo                 18     4.9    1670  1669  1643  1631  1608  1593  1572  1549  1510                          1      2      4      2      462    Cards
Terra Mystica        12     1.14   1793  1751  1733  1722  1636  1599                                            3.97   5      1      1       52    Hex board
Taknoko               8     2.7    1851  1849  1786  1750  1693  1628  1752                                      2      3      2      1       92
Hearts           WCG  -            1691  1603  1575  1553  1528  1494  1446                                                                  100
Canasta               -      .74   1857  1833  1811  1712  1611  1541                                            2      2      4      3       57
Connect 4             -     4.4    2024  2010  1945  1830  1802  1726                                            1      5      0      0       59    Square board and tokens
Great Western Trail   -      .38   1869  1860  1828  1865  1604  1560                                            3      3      3      3       60
Barrage               -      .28   1832  1730  1660  1628  1598  1560                                            3      5      2      1       41    Board and tokens
Age of Innovation     -      .19   1880  1809  1727  1682  1649  1572                                            4      5      1      1       42    Hex board and tokens
Darwin's Journey      -      .87   1793  1751  1745  1702  1638  1598                                            4      5      1      1       52    Hex board and tokens
Barrage               -      .28   1836  1730  1660  1628  1598  1562                                            3      5      2      1       41
Obsession             -      .29   2082  2056  1808  1761  1669  1550                                            3      5      1      1       33    Tokens and cards
Dice Forge            -     2.6    1939  1832  1785  1750  1673  1604                                            2      2      4      0       56
Warchest              -      .50   1761  1752  1737  1687  1604                                                  2      3      2      0       24    Hex board, tokens, cards
Beyond the Sun        -      .23   1751  1708  1659  1619  1597                                                  3      4      1      2       23
Xianqi         World  -            2783  2754  2624  2610  2577
Checkers       World  -            2433  2430  2403  2377  2351
Reflection            -      .27   2000  1960  1865  1787  1573                                                  3      3      0      0       24    Square board and pieces
Chinese Checkers      -      .15   1683  1635  1609  1562                                                        1      5      0      2       11    Hex board and tokens
Scrabble       World  -            2174  2162  2108  2077
Dungeon Twister       -      .047  1629  1621  1606  1471                                                        3      4      1      3        9    Board, tokens, and cards
Galactic Cruise       -      .067  1836  1789  1740  1652                                                        4      4      1      2        8    Ship design
Barca             BS  -     <.0001 1704  1547  1317                                                                                                 Square board. Fairy chess. 110 rated games
Checkers              -      .44   1738  1598                                                                    1      4      1      0        2    Square board
Scythe                -      .79   1712  1696                                                                    3      4      2      3        2
Tumbleweed            -            1615  1601                                                                    3      5      0      0             Hex board
Hanabi                -    10.5                                                                                  2      3      3      4        0    Cards
Bandito               -     2.9                                                                                  1      3      3      4        0
Turing Machine        -      .78                                                                                 2      5      1      0        0
Trench                -      .002                                                                                                              0    Square board and pieces
King's Color          -     0                                                                                                                  0    Hex chess. Pieces change
Day and Night         -     0                                                                                                                  0    Square board. Row and diagonal building
Push Fight            -     0                                                                                                                  0    Square board. Pieces exert forces
Tablut                -     0                                                                                                                  0    Square board and pieces. Ancient.
Mahjong               -      .004                                                                                4      3      4      3

                  Depth  Matches    #1    #2    #4    #8    #16   #32   #64  #128  #256  #512 #1024 #2048 #3072  Comp-   Strat-  Luck  Commun-   # of rated
                         million                                                                                plexity  egy           ication    players

Ratings are from boardgamearena.org unless denoted otherwise. "World" means world ratings, "BS" means boardspace.com, and WCG means worldofcardgames.com.

Chess ratings are from FIDE.


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Data from Wikipedia unless otherwise specified.