Book excerpt: Based on the authors' experiences in developing and teaching Symbian OS, this practical guide is perfect for programmers and provides a series of example-based scenarios that show how to develop Symbian applications. Exercises walk the reader through the initial development of a console-based card game engine to a graphical user interface(GUI)-based, two player blackjack game operating over a Bluetooth connection between two mobile phones Addresses how Symbian offers a number of different variants to allow for different user interfaces and screen savers - the most prevalent of these is S60 Discusses how the move toward 3G technology has resulted in an increasing need for mobile application development for S60 devices.