A physicist's study of Chess960, a variant that randomizes starting piece positions, shows that not all configurations are equally fair to white and black players. By evaluating complexity using chess software, the research identifies positions that could balance the game better. This challenges the assumption that randomization alone ensures equity in the popular format.
Standard chess begins with a symmetric arrangement of pieces: rooks, knights, and bishops on the edges, followed by the king and queen in the center. This setup allows top players to memorize opening moves, often resulting in predictable games. In the 1990s, grandmaster Bobby Fischer introduced Chess960, which shuffles the back-row pieces while adhering to rules for bishops, rooks, and kings, creating 960 possible starting positions. The variant has gained traction, with figures like Magnus Carlsen participating in tournaments to emphasize skill over preparation.
Marc Barthelemy, a physicist at Paris-Saclay University, analyzed every Chess960 position using the open-source engine Stockfish. He measured complexity by comparing the ease of finding the best and next-best moves for each side. Positions where both moves are equally accessible pose tougher decisions. Barthelemy's findings reveal that while white typically holds a first-move advantage in standard chess, some Chess960 setups amplify this edge, while a handful slightly favor black. "Not all positions are equivalent," Barthelemy notes.
The most complex arrangement is BNRQKBNR, while QNBRKBNR offers the best balance between players' difficulties. These could guide tournament organizers toward fairer matches. However, Vito Servedio from the Complexity Science Hub in Austria contends that Chess960's randomness inherently levels the playing field. "It’s more fair because you start with your opponent on the same foot," Servedio says, adding that grandmasters can't prepare for all openings.
Surprisingly, the traditional chess position ranks average in both fairness and complexity among the 960 options. "Very surprisingly, the standard chess position is not particularly remarkable," Barthelemy observes. Giordano de Marzo at the University of Konstanz questions whether this complexity metric fully captures human difficulty, suggesting that positions with a single critical move might be harder. He speculates that longer thinking times in complex setups could validate the approach. The study appears in arXiv (DOI: 10.48550/arXiv.2512.14319).