Lion specific features

I am developping a Mac application requiring Mac OS 10.6. However I am interested to add a Lion specific feature (fullscreen support). What is the way to properly manage that (I am planning to use the Mac App Store):

• 2开发者_StackOverflow different versions?
• a "special" version combining 2 version and using automatically the right one depending of the system?

Thanks

Set Base SDK to Lion, but the Deployment Target to the oldest version you want to support, and the newer features are available via weak linking