Apple Inc. removed Fortnite from the App Store today, prompting a lawsuit by the game’s creator, Epic Games Inc. The moves escalate a dispute between the two companies that had been brewing in recent weeks.

The disagreement stems from a longstanding App Store rule saying most apps must offer billing through Apple and pay the company 30% of revenue. On Thursday morning, Epic began offering customers a way to directly buy items for Fortnite and circumvent the fees. Hours later, Apple pulled the app.

Apple said in an emailed statement that it removed Fortnite because Epic’s changes had the “express intent of violating the App Store guidelines.” Apple said its store helped enable Epic’s success over the last decade and that it offers a “level playing field” for businesses.

Epic filed a lawsuit in a California district court, alleging that Apple’s stronghold on its app store and related customer payments is anti-competitive. Epic said it isn’t seeking money but for Apple’s practices to be stopped. If not for Apple’s “illegal restraints,” Epic would provide a competing app store on Apple devices, according to the lawsuit.

Epic’s flagship game, Fortnite, is a cultural phenomenon. The game has had more than 350 players over the years, the lawsuit said. The game’s removal from the App Store means losing access to more than a billion iPhone and iPad customers. Sales through Apple’s store generated $32.8 billion for developers in the first half of 2020, up more than 20% from a year earlier, according to market research firm Sensor Tower.

Grievances over the fees Apple charges developers have reached a boiling point. For years, developers have complained about Apple’s 15% to 30% fees for the App Store, and Chief Executive Officer Tim Cook was recently grilled over the issue at a U.S. Congressional hearing alongside other technology chiefs. Apple is also facing scrutiny from officials in Europe over antitrust complaints, an investigation that Epic Chief Executive Officer Tim Sweeney has openly supported. Spotify Technology SA, which has waged a similar battle with Apple, said in a statement it supports Epic’s crusade.

Sweeney has also criticized Google, which maintains a similar policy as Apple. He described the two companies as a duopoly in an interview with Bloomberg Television last month.

Epic told customers on Thursday it would begin offering a direct purchase plan for items in Fortnite and that instead of paying fees to Apple and Google, it would pass on the savings to customers. Epic offered discounts of as much as 20% through its service. Fortnite was still available on Google’s app store as of this afternoon.

The lawsuit against Apple invokes George Orwell’s “1984.” Shortly after Fortnite was pulled, the game’s official Twitter account promoted a new video short called Nineteen Eighty-Fortnite, a cheeky shot at a famous Apple advertising campaign.