Warner Bros. released a mobile game based on HBO's Westworld series yesterday, which isn't something we'd normally pay much attention to. We are in this case, however, because the launch of the game was followed shortly by the launch of a lawsuit, filed by Bethesda, alleging that the game is "a blatant rip-off of Fallout Shelter," that's actually built on the same code.

The suit, available via Polygon, alleges that Westworld features "the same or highly similar game design, art style, animations, features, and other gameplay elements as Fallout Shelter." But the similarities are more than skin deep. Both games were developed by Behaviour Interactive, and Bethesda claims that Warner hired Behaviour to develop the Westworld game specifically because it had made Fallout Shelter.

"Warner Bros. expected and relied on Behaviour’s ability to reuse and/or leverage Bethesda’s computer code, game designs, and other intellectual property as the foundation for the Westworld game," the suit says. "This unauthorized copying and sharing enabled Behaviour to shorten its development cycle, reduce costs, and decrease the game’s time to market and to command a built-in consumer base by making the Westworld mobile game’s gameplay experience and look-and-feel the same as or substantially similar to Fallout Shelter."

The lawsuit examines the many similarities between Westworld and Fallout Shelter in detail, but what makes the case seem particularly egregious is Bethesda's allegation that Westworld contains the same bugs as Fallout Shelter did when it was launched. One such bug causes the view to be off-center and out of focus at startup, "as if a camera capturing the scene had been inadvertently pointed to the lower right foreground and then slowly refocuses on the central image."

"The identical problem appeared in initial versions of Fallout Shelter but was addressed before Fallout Shelter was released to the public," the lawsuit states. "While this error was ultimately fixed in subsequent builds of Fallout Shelter, the appearance of the bug in the Westworld game demo makes clear that the Fallout Shelter source code was used by Behaviour in developing the Westworld game."

I can't test either game to determine if that claim is true, but I don't think it's the kind of thing that a competent lawyer would throw into a lawsuit without being able to demonstrate proof. And if Bethesda can prove it, that's pretty damning evidence that Behaviour did in fact build Westworld using Fallout Shelter source code.

Bethesda is seeking damages arising from breach of contract and copyright infringement, and also wants Westworld removed from Google Play and the App Store. I've reached out to Warner and Bethesda for comment, and will update if I receive a reply.