When Microsoft finally announced Xbox One games at E3, most of the announcements weren’t surprising. A new Halo game was teased, Microsoft had gotten Capcom to make Dead Rising 3 an exclusive, and the microtransaction-riddled launch trio of Forza 5, Ryse, and Crimson Dragon were all there, as well as a multitude of third-party titles. Along with these triple-a showpieces, though, was a title full of creativity and promise.

Project Spark brought bright colors to Microsoft’s E3 conference and showed off what Microsoft Studios can do at its best. The game is being billed as a sandbox/creation game, where players can build worlds and populate them with creatures who follow set rules. Demonstrations of Project Spark have shown that players will be able to create a wide variety of gameplay scenarios with a specific visual flair.

Beta sign-ups for Project Spark began in June, shortly after its announcement at E3. Today Microsoft has finally announced that the game’s beta test has begun.

Unfortunately for new Xbox One owners, the Project Spark beta is exclusive to PC at this time – and only PCs running Windows 8.1. Beta participants who meet those requirements can begin playing today. Xbox One owners will have to wait until sometime “early next calendar year” to get their hands on the beta.

The Project Spark beta includes several aspects of the full game. Players will be able to create game types, shape game world terrain, and create simple AI behaviors for characters. Sharing and co-op with other beta participants will also be enabled, allowing players to experience what others have created.