Phil Spencer, the head of Microsoft’s Xbox division, took the stage at Build 2016 today to talk about the benefits of developing games on Windows, and Spencer made a point to highlight the openness of the platform.

“Windows is and will continue to be an open development ecosystem where anyone can build, deploy, sell, and service their games and applications,” Spencer said.

While Spencer may have been speaking to the audience at Build, his comments were likely directed at one person in particular: Epic Games founder Tim Sweeney.

Earlier this month, Sweeney penned a lengthy op-ed for The Guardian in which he slammed Microsoft’s Universal Windows Platform (UWP) for being “a closed platform-within-a-platform,” saying that if Microsoft “does not commit to opening PC UWP up in the manner described here, then PC UWP can, should, must and will, die as a result of industry backlash.”

Spencer quickly rejected Sweeney’s claims on Twitter on promised that Microsoft would reveal more of its plans for UWP and game development at build, and so far that certainly seems to be the case.

“Through the Universal Windows Platform,” Spencer said in his Build keynote, “our plan is to deliver games that will run better on Windows with more predictable performance; more robust install, uninstall, and servicing capability through a modern application platform; greater safety for users through a protected runtime environment; and distribution of modern desktop applications on any store, including the Windows Store and via any development deployment mechanism.”

Xbox Dev Mode: DIY console game development

As part of Microsoft’s commitment to making Windows game development accessible to everyone, Spencer announced the introduction of Xbox Dev Mode, a new feature that will allow anyone to turn their retail Xbox One console into a development kit.

“Our commitment to turn every Xbox One into a dev kit isn’t a hobby, it’s a commitment,” Spencer said. “It’s a commitment to empower every developer on the planet to reach the largest addressable TV audience on one open app platform.”

“But enabling developers to create and deploy UWP apps and games on Xbox One is just the beginning. With the upcoming Windows 10 anniversary update, we will continue our progress that brought Xbox Live to all Windows device and the Xbox App to Windows 10 where millions of gamers are connected around the world. We will also be adding a single unified store across devices, giving developers new features and consumers a consistent experience.”

A preview of Xbox Dev Mode will be available starting today.

Spencer noted that Microsoft would also be announcing other new features coming to Xbox in the anniversary update at this year’s E3 in June.

Screenshot via Build 2016 livestream