No Windows 8.1? No problem
The Project Spark beta is far from new at this point, but it's no longer restricted to Windows 8.1 users. Some 250,000 people have signed up and I imagine many more will express their interest now that the beta can be experienced on Xbox One as well. Do that here, if you'd like.
Note: if you already have a code for Windows, you're golden. Just follow these instructions. I haven't yet touched Project Spark but looking over this montage, people seem to be making great use of the provided tools. Shout out to the person keeping the StarFox dream alive.