Found this: https://www.lexology.com/library/detail.aspx?g=05891d4f-1658...

A federal court in Texas recently ruled that the structure and game play of a card game are not protected by copyright law in DaVinci Editrice S.r.l vs. Ziko Games, LLC et al.

DaVinci Editrice S.r.l (DaVinci) published Bang!, a role-playing card game using Wild West themes, in 2002. Players in Bang! are assigned one of four roles, each with its own winning condition. Each player is also assigned a Wild West-themed character, such as “Calamity Janet” and “Willy the Kid,” each with its own abilities. The game received critical praise and commercial success.

Yoka Games, a Chinese company, and its U.S. distributor, Ziko Games, LLC (Ziko) later introduced Legend of the Three Kingdoms (LOTK), a card game with rules nearly identical to Bang! but set in ancient China. Players are assigned one of four roles with the same functions and winning conditions as in Bang!, and are assigned characters with individualized abilities, with different names and artwork to reflect the different setting.

DaVinci sued Ziko for copyright infringement, asserting that LOTK copied protected features of Bang! Copyright law protects original expression, but does not protect ideas or functional elements such as procedures, processes, systems, or methods of operation. Game mechanics and rules are not entitled to copyright protection, but expressive elements may be copyrightable, including game labels, design of game boards, playing cards, and graphical works, as well as elements of the characters – if they are sufficiently developed. Copyright does not protect “stock” characters.

The court determined that Ziko’s game did not infringe any of the protectable elements of Bang! The game play and interactions of the roles and characters in Bang! are not sufficiently detailed or developed to be protectable expressive content, but instead are unprotectable game mechanics and rules. The characters and roles in Bang! are not considered to have delineated personalities, temperaments, back stories, or other features typical of characters in movies and books that can make those characters protected. Ziko copied unprotectable elements such as rules and system of play, but did not copy aspects of the roles and characters which are expressive (and therefore copyrightable), such as the associated artwork. By adopting an ancient Chinese theme in LOTK, Ziko was able to avoid copyright liability while copying the basic structure and game play in Bang!

For game designers and publishers, this decision clarifies the limitations of copyright law in protecting card games. Copyright law can be effective in protecting the expression in a game (artwork, appearance), but does not protect rules and game play. Detailed original characters may be protected, but not aspects of the character that exist just to drive the system of play, such as how strong they are or how difficult they are to defeat. Trademark law can be effective in protecting your brands (company name, game titles). Patent law can protect the rules and methods of game play, and patents directed to methods of playing card games have been issued (Magic: The Gathering, Apples to Apples). However, the courts’ evolving interpretation of patent-eligible subject matter has made obtaining patent protection on rules and methods of game play more challenging. Game designers and publishers can best protect their products with a combination of intellectual property rights, rather than relying upon copyright alone.