Game publisher Bethesda is suing Warner Brothers over a game based around the HBO series Westworld.
Included in the legal challenge is Canadian developer Behaviour Interactive, which helped Bethesda develop Fallout Shelter in 2014.
Warner and Behaviour Interactive have not yet responded to a request for comment from the www.surprizebd.tk
Bugs claim
The Westworld game gives players the job of managing the titular theme park and its robotic inhabitants.
The facility managed by the player can be expanded underground and includes many of the locations seen in the TV series.
Many reviews of the game mentioned its similarity to Bethesda's Fallout Shelter, which gives players the job of managing and expanding an underground facility.
In legal papers widely shared online, Bethesda alleges this similarity is more than skin deep and the game uses code Behaviour wrote when creating Fallout Shelter.
In some cases, it says, bugs seen in early drafts of Fallout Shelter code also crop up in the Westworld game.
Bethesda claims the Westworld game infringes its copyright and Behaviour has:
misappropriated trade secrets
broken contractual agreements limiting what it can do with the Fallout code
indulged in unfair competition
In a statement given to Variety, Bethesda said it would "vigorously protect its legal rights in the valuable intellectual properties it owns, and take legal action whenever those rights are being infringed".
It is seeking substantial damages and a jury trial.