Polish developer People Can Fly has announced that it’s making a game for Sony Interactive Entertainment based on an IP that Sony owns, though it remains to be seen what the game is.

In a statement, People Can Fly said the new game is in the works under the codename Project Delta. As part of the agreement between People Can Fly and Sony, there will be a milestone process. Details weren’t provided, but this is a common practice where development progress is reviewed at certain intervals.

People Can Fly did not divulge the specific scope and terms of its milestone agreement with Sony but said it does not differ much from standard work-for-hire projects of this nature. The Polish studio has a lot of experience in this department, as it has worked with big game companies on projects before, including Gears of War: Judgment with Microsoft, Fortnite: Saves the World with Epic, and Outriders with Square Enix. People Can Fly is also working with PUBG company Krafton on a new game codenamed Project Echo and is collaborating with The Coalition on Gears of War: E-Day.

The official word is that People Can Fly’s game with Sony is “based on the intellectual property rights owned by” Sony, but there is no word on what it is. It sounds like it could be an existing Sony franchise, but that is never stated outright in the document. Another document from People Can Fly describes the agreement as covering work to create a prototype.

Founded in 2002, People Can Fly released the first-person shooter Painkiller in 2004 as its first game. Epic Games took a majority ownership of the company in 2007 following the cancellation of People Can Fly’s game Come Midnight with now-defunct publisher THQ. In 2012, Epic bought People Can Fly and re-named it Epic Games Poland, but in 2015, People Can Fly became independent again.