(Almost like HTML5, but in .NET). Now, portable mobile graphical programming is also possible by an open source library:
CocosSharp: Xamarin Forks Cocos2D-XNA
"Xamarin has forked Cocos2D-XNA, a 2D/3D game development framework, creating a cross-platform library that can be included in PCL projects.
Xamarin has decided to stop contributing to Cocos2D-XNA, forking instead the framework and creating a new library called CocosSharp which is open sourced on GitHub under a MIT license. For the beginning, Xamarin has refactored the source code in order to create “an idiomatic version of Cocos2D for the .NET environment.”
Introducing CocosSharp | Xamarin Blog:
"CocosSharp blends the power of the Cocos2D programming model with C# and the .NET Framework."