Microsoft first announced Project Spark, their free game creation tool, at E3 in June. At the time, we were impressed with how the tool set had been designed to allow for quick creations of worlds, characters and the rules needed to make a game. Microsoft opened up sign ups to beta test Project Spark soon after E3 and promised that the Windows 8 port would be ready for beta testing in October.
Obviously, Microsoft missed that date but today it has finally launched the first phase of the Project Spark beta for Windows 8.1. People who own a Windows RT device like Microsoft's Surface and Surface 2 tablets won't be able to run Project Spark during this phase of the beta test. Microsoft has said that "hundreds of thousands of fans" have already signed up to participate. However, a post on the official Project Spark Twitter account says that Windows 8.1 beta invites will only be sent out to a few of those people at first.
@Matth3wUU Yes, but we're starting with a very small group and will slowly increase the number of invites over the next several days/weeks.— Project Spark (@proj_spark) December 3, 2013
People who still want to take part in the closed beta test can go to the JoinProjectSpark.com site to sign up. Project Spark is also supposed to be released for the Xbox One and Xbox 360 consoles, although that is not expected to happen until sometime in 2014.
Source: Xbox Wire