Building the Crystal Ball app will teach you how to use the Objective-C language and the Xcode and Interface Builder tools. You will also learn core concepts such as a design pattern called Model-View-Controller, View hierarchy, View Controller life-cycle. In addition, you will learn how to connect views/controls to code, create animations, respond to touch and motion events. Towards the end you will have finished creating a fun app that will get you oriented with world of iOS development.