GeneSys is a real-time game-construction toolkit created in .NET and XNA 3.1. While the base tool requires this platform, games developed in it can be ported to other supported platforms implicitly (such as Xbox 360 and Zune) and explicitly (Android, Mac OSX, iPhone, etc).
GeneSys reaches for that Holy Grail of game development: to be able to develop an entire game from start to finish without having to restart the tool a single time. Forget making games in months, let's try days or even hours.
Furthermore, at its ideal, GeneSys requires no programming...and at its best, no typing! That's a tall order but why not shoot for the stars, it beats settling for the swamp.
The development log and tutorials of GeneSys are being committed to a book for publishing later this year or early 2010.