Microsoft has now launched the Windows 8.1 closed beta version of its Project Spark game creator via the Windows Store



From Neowin:

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.

  Microsoft launches Windows 8.1 closed beta version of Project Spark