Othello

Two players compete, using 64 identical game pieces ("disks") that are light on one side and dark on the other. Each player chooses one color to use throughout the game. Players take turns placing one disk on an empty square, with their assigned color facing up. After a play is made, any disks of the opponent's color that lie in a straight line bounded by the one just played and another one in the current player's color are turned over. When all playable empty squares are filled, the player with more disks showing in their own color wins the game.

• Title — Reversi • Italic Title — no • Years — (or earlier)—present • Genre — * Board game • Abstract strategy game • Mind sport • Players — 2 • Setup Time — 28, and it has a game-tree complexity of approximately 10 58. Mathematically, Othello is solved up to 8x8 board. On 4×4 and 6×6 boards under perfect play, the second player wins. On 8x8 board, the game results in draw under perfect play, according to an arXiv paper. The first of these proofs is relatively trivial, the second dates to around 1990, and the last one was done in 2023. When generalizing the game to play on an n×n board, the problem of determining if the first player has a winning move in a given position is PSPACE-complete.

The World Othello Championship (WOC), which started in 1977, was first organized by the Japan Othello Association. From 1978 until 2004, the World Othello Championship was organized by the Othello TD group and Anjar Co. In 2005, the World Othello Federation took over the responsibility for the WOC. From 1977 to 1986, each country could send one player to participate in the WOC. From 1987, each country could send up to three players to participate. In 1987, the title WOC team championship started. In 2005, a female championship category was added to the WOC. From 2006, each World Othello Federation member could send a full team of up to four players. In 2016, a youth champion title was added to the WOC. The WOC was cancelled in 2020 and 2021 due to the COVID-19 pandemic. • Year — Location — World Champion — Team — Runner-up — Female Champion — Youth Champion • 1977 — Tokyo — Hiroshi Inoue — Thomas Heiberg • 1978 — New York City — Hidenori Maruoka — Carol Jacobs • 1979 — Rome — Hiroshi Inoue — Jonathan Cerf • 1980 — London — Jonathan Cerf — Takuya Mimura • 1981 — Brussels — Hidenori Maruoka — Brian Rose • 1982 — Stockholm — Kunihiko Tanida — David Shaman • 1983 — Paris — Ken'Ichi Ishii — Imre Leader • 1984 — Melbourne — Paul Ralle — Ryoichi Taniguchi • 1985 — Athens — Masaki Takizawa — Paolo Ghirardato • 1986 — Tokyo — Hideshi Tamenori — Paul Ralle • 1987 — Milan — Ken'Ichi Ishii — United States — Paul Ralle • 1988 — Paris — Hideshi Tamenori — United Kingdom — Graham Brightwell • 1989 — Warsaw — Hideshi Tamenori — United Kingdom — Graham Brightwell • 1990 — Stockholm — Hideshi Tamenori — France — Didier Piau • 1991 — New York City — Shigeru Kaneda — United States — Paul Ralle • 1992 — Barcelona — Marc Tastet — United Kingdom — David Shaman • 1993 — London — David Shaman — United States — Emmanuel Caspard • 1994 — Paris — Masaki Takizawa — France — Karsten Feldborg • 1995 — Melbourne — Hideshi Tamenori — United States — David Shaman • 1996 — Tokyo — Takeshi Murakami — United Kingdom — Stéphane Nicolet • 1997 — Athens — Makoto Suekuni — United Kingdom — Graham Brightwell • 1998 — Barcelona — Takeshi Murakami — France — Emmanuel Caspard • 1999 — Milan — David Shaman — Japan — Tetsuya Nakajima • 2000 — Copenhagen — Takeshi Murakami — United States — Brian Rose • 2001 — New York City — Brian Rose — United States — Raphael Schreiber • 2002 — Amsterdam — David Shaman — United States — Ben Seeley • 2003 — Stockholm — Ben Seeley — Japan — Makoto Suekuni • 2004 — London — Ben Seeley — United States — Makoto Suekuni • 2005 — Reykjavík — Hideshi Tamenori — Japan — Kwangwook Lee — Hisako Kinoshita • 2006 — Mito — Hideshi Tamenori — Japan — Makoto Suekuni — Toshimi Tsuji • 2007 — Athens — Kenta Tominaga — Japan — Stéphane Nicolet — Yukiko Tatsumi • 2008 — Oslo — Michele Borassi — Japan — Tamaki Miyaoka — Liya Ye • 2009 — Ghent — Yusuke Takanashi — Japan — Matthias Berg — Mei Urashima • 2010 — Rome — Yusuke Takanashi — Japan — Michele Borassi — Jiska Helmes • 2011 — Newark — Hiroki Nobukawa — Japan — Piyanat Aunchulee — Jian Cai • 2012 — Leeuwarden — Yusuke Takanashi — Japan — Kazuki Okamoto — Veronica Stenberg • 2013 — Stockholm — Kazuki Okamoto — Japan — Piyanat Aunchulee — Katie Wu • 2014 — Bangkok — Makoto Suekuni — Japan — Ben Seeley — Joanna William • 2015 — Cambridge — Yusuke Takanashi — Japan — Makoto Suekuni — Yoko Sano Rose • 2016 — Mito — Piyanat Aunchulee — Japan — Yan Song — Zhen Dong — Masaki Wada • 2017 — Ghent — Yusuke Takanashi — Japan — Akihiro Takahashi — Misa Sugawara — Akihiro Takahashi • 2018 — Prague — Keisuke Fukuchi — Japan — Piyanat Aunchulee — Misa Sugawara — Keisuke Fukuchi • 2019 — Tokyo — Akihiro Takahashi — Japan — Yusuke Takanashi — Joanna William — Akihiro Takahashi • 2020 — Cancelled • 2021 — Cancelled • 2022 — Paris — Kento Urano — Japan — Arthur Juigner — Katie Pihlajapuro — Fuyumi Okudaira • 2023 — Rome — Yasushi Nagano — Japan — Rujipas Aunchulee — Hisako Kinoshita — Osuke Kawazoe • 2024 — Hangzhou — Seiya Kurita — Japan — Yusuke Takanashi — Hisako Kinoshita — Yo Tomita • 2025 — Ankara — Seiya Kurita — Japan — Yusuke Takanashi — Miu Hisamatsu — Singapore Calvin Koh Ding Sheng

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