Call for New Games

Hi all,

I'm starting a thread to collect requests for new games and plans for upcoming games. We will keep this updated as new games get released, and as requests come in (please feel free to comment on this thread to add a request).

Games we would like to add to OpenSpiel:

- [Mahjong](https://en.wikipedia.org/wiki/Mahjong)
- Pursuit-evasion game played on a graph or grid

Implementing one of these games is a great way to get involved with contributing to OpenSpiel. If you would like to volunteer to implement one, please contact us and let us know as we might already be working on them.

Games that have been added since posting this thread:
- [2048](https://en.wikipedia.org/wiki/2048_(video_game)) (Thanks @Jazeem. PR now merged: https://github.com/deepmind/open_spiel/pull/894)
- Checkers (thanks @Jazeem! PR now merged: https://github.com/deepmind/open_spiel/pull/861)
- Euchre (thanks @jhtschultz! Added in https://github.com/deepmind/open_spiel/commit/a3dbb1b7483b3b02077a92bb3a84389907afb79b)
- Mancala (Kalah) (thanks @Jazeem! see https://github.com/deepmind/open_spiel/pull/841)
- [Nim](https://en.wikipedia.org/wiki/Nim) (thanks @acforvs! PR merged: https://github.com/deepmind/open_spiel/pull/868)
- Phantom Go (thanks @Syor! PR now merged: https://github.com/deepmind/open_spiel/pull/867)
- [Dou dizhu](https://en.wikipedia.org/wiki/Dou_dizhu): (Thanks @rezunli96! PR merged: https://github.com/deepmind/open_spiel/pull/969)
- [Mensch-Ärgere-Dich-Nicht](https://en.wikipedia.org/wiki/Mensch_%C3%A4rgere_Dich_nicht) (Thanks @thorsten-j ! PR merged: https://github.com/deepmind/open_spiel/pull/915)
- Dominoes (Thanks @morLev ! PR merged: https://github.com/deepmind/open_spiel/pull/1018)
- [Nine Men's Morris](https://en.wikipedia.org/wiki/Nine_men%27s_morris). PR merged: https://github.com/deepmind/open_spiel/pull/1079
- [EinStein würfelt nicht!](https://en.wikipedia.org/wiki/EinStein_w%C3%BCrfelt_nicht!) (Thanks @giogix2! PR merged: https://github.com/google-deepmind/open_spiel/pull/1289)
- [Cribbage](https://en.wikipedia.org/wiki/Cribbage). Done! Added in https://github.com/google-deepmind/open_spiel/commit/82819d0121744531affb6dffa4ea52b159ab8066
- Latent Tic-Tac-Toe (see description in [this paper](http://mlanctot.info/files/papers/nips09mccfr.pdf)) Done! Added in https://github.com/google-deepmind/open_spiel/pull/1361. Thanks @giogix2!
- [Yacht](https://en.wikipedia.org/wiki/Yacht_(dice_game)) (Thanks @gmweinberg! PR merged: https://github.com/google-deepmind/open_spiel/pull/1403)
- Ant foraging on a grid (Thanks @abhaygoudannavar ! PR merged: https://github.com/google-deepmind/open_spiel/pull/1470)
- [Chinese Dark Chess](https://en.wikipedia.org/wiki/Banqi) (Thanks @kvr06-ai PR merged: https://github.com/google-deepmind/open_spiel/pull/1501)
- [Shogi](https://en.wikipedia.org/wiki/Shogi) (Thanks @gmweinberg! PR merged: https://github.com/google-deepmind/open_spiel/pull/1509)
- [Chinese Chess](https://en.wikipedia.org/wiki/Xiangqi) (Thanks @Arahan-kujur! PR merged: https://github.com/google-deepmind/open_spiel/pull/1512)
- [Chinese Checkers](https://en.wikipedia.org/wiki/Chinese_checkers) (Thanks @kvr06-ai! PR merged: https://github.com/google-deepmind/open_spiel/pull/1513)
- Capture-the-Flag (Thanks @kvr06-ai ! Games merged in https://github.com/google-deepmind/open_spiel/commit/7c02e7aa7526146e6961d4800ca9cd2342bf71f6)
- Pursuit-evasion in 2D space (Thanks @aeyjeyaryan ! Game merged in https://github.com/google-deepmind/open_spiel/commit/e8bd22c88207f71a1903c685fd38d25b232c010d)

With these additions, OpenSpiel now has over 100 games.