Valve has just revealed Source 2, a new, more powerful game engine, at Game Developers Conference 2015.

The Source 2 engine is a successor to the original Source engine, which debuted in June 2004 with the launch of Counter-Strike: Source. Games running off the original Source engine include Valve classics like Half-Life 2 and the Left 4 Dead series, as well as third-party and independent releases such as Garry's Mod, Dear Esther, The Stanley Parable and Titanfall.

"With Source 2, our focus is increasing creator productivity," said Jay Stelly of Valve in a press release today. "Given how important user generated content is becoming, Source 2 is designed not just for the professional developer, but enabling gamers themselves to participate in the creation and development of their favorite games."

Valve says Source 2 will be "available for free to content developers," pointing to similar recent announcements about Epic's Unreal engine and the Unity engine.

Valve also announced a special version of Source 2 that will be compatible with Vulkan, a "cross-platform, cross-vendor 3D graphics API that allows games developers to get the most out of the latest graphics hardware."

Valve provided no info on when Source 2 will be available or whether it has any projects using the engine in the works.