This is the third part of Peter Kuhn's article series to prepare you for Microsoft's new Windows Phone 7 exam which will be available starting July 14th. This part of the exam preparation is all about working with the platform and its APIs. Using sensors and touch input is really made easy by the available APIs, but that doesn't mean that you cannot create complex applications using it. Tasks seem equally easy to work with at first, but they have some subtle requirements for choosers you need to match; in the next part you'll also see how the application life cycle needs to be taken into consideration for them. Finally, the navigation concept is something you should be able to work with blindfolded – it's really one of the fundamental features of the platform.