https://www.techdirt.com/articles/20170922/09531338270/idea-v-expression-game-studio-bluehole-gets-fur-up-over-epic-games-putting-100-vs-100-player-battle-royale-into-game.shtml

Of all the things that most people get wrong about copyright law, the idea/expression dichotomy has to rank near the top. The confusion over this is easily explained by the pervasive ownership culture that has emerged organically from an intellectual property ecosystem that only moves in the direction of more protectionism. Because of that culture, most people simply assume that the creation of the idea is itself a copyrightable thing, rather than the reality which is that copyright only applies to specific expression. The useful example at hand is that one cannot copyright a superhero named after an animal that wears a mask and a cape, but one can copyright Batman, particularly any books, comics, or movies in which Batman is depicted.

As already stated, this reality evades many people. But it probably shouldn't evade those in industries dominated by copyright, such as the video game industry. Despite that, Bluehole, developers of the wildly popular PlayerUnknown's Battlegrounds developer, appears to have its fur up over another studio, Epic Games, releasing a "battle royale" game mode for its Fortnite title.