Microsoft’s popfly is an easy way to create widgets and mashups using Silverlight. With Popfly Game Creator, it is adding a simple Web-based authoring environment for creating casual arcade-style games.
The tool is built for non-programmers so that anyone can create a game, and is particularly aimed at kids and teenagers. It is entirely browser-based. You create a game using predefined templates that can be modified, and when you are satisfied, you hit play to run the code. The games run in Silverlight and will be hosted at Popfly, but are embeddable anywhere on the Web.