"International" or "Western" chess itself is one of a family of games which have related origins and could be considered variants of each other.
[4][5] Fairy chess variants tend to be created for problem composition rather than actual play.
[2] Over time, as the game spread geographically, modified versions of the rules became popular in different regions.
[2] Other games in the chess family, such as shogi (Japan), xiangqi (China), and ouk chatran (Cambodian) are also developments from chaturanga made in other regions.
In most cases the creators are attempting to create new games of interest to chess enthusiasts or a wider audience.
[9] Some variations are created for the purpose of composing interesting puzzles, rather than being intended for full games.
Physical models of common fairy pieces are sold by major chess set suppliers.
[11] Likewise Crazyhouse has seen prize-funded unofficial world championship tournaments with top grandmasters and experts of the game on chess.com and lichess.
[17] The AI included in Zillions of Games is able to play almost any variant correctly programmed within it to a reasonable standard.
[16] Some variants, such as 5D Chess with Multiverse Time Travel, are implausible or even impossible to play physically and exist primarily as video games.
[25] In The Chessmen of Mars author Edgar Rice Burroughs describes Jetan which depicts a war between two races of Martian.
More commonly specifics of fictional variants are not detailed in the original works, though several have been codified into playable games by fans.
Fictional chess variants can involve fantastical or dangerous elements that cannot be implemented in real life.
The Chessmen of Mars describes a form of Jetan where the pieces are human beings and captures are replaced by fights to the death between them.
The Doctor Who episode "The Wedding of River Song" depicts "Live Chess", which introduces potentially lethal electric currents into the game.