SilverTicTacToe was originally created using Visual Studio "Orcas" beta 1,
Silverlight 1.1 Alpha, the Silverlight Tools Alpha and Expression Blend 2 May Preview.
Later it was updated to 1.1 refresh, and then to version 2.0 Beta 1 and 2 and
finally the release version of Silverlight 2.
To play SilverTicTacToe online you need the Silverlight 2.0 plugin or a higher compatible version.
If you wish, you can even download the sourcecode here.
Just as a disclaimer, this code was created using the Alpha version of Silverlight 1.1. As Silverlight
and my understanding of Silverlight development progressed, I would not consider the code as best-practice.
Just so that you know ;-)