Sorry for the wait! It's now live and ready to be played. Currently it's only a Windows build. Pop by the forums to let us know what you liked and what you didn't.
I've been pushing hard to get another version of the demo out. It will still be a while, since it's going to include the level editor. It's also going to have a redesign in how the levels are saved out, so that's going to be a big change. Hopefully I'll have something to post about it soon.