We have seen how animation can be used to produce a more vibrant, engaging user interface, but this is only scratching the surface of what can be done by animating the changes in the property values of UI elements. Despite the relatively modest number of properties we can animate, with a little imagination we can create effects that are simple, but which fundamentally alter the way we engage with the Apple Watch.

We have already seen in Chapter 2, Hello Watch, how simple it is to overcome the lack of a completion handler in calls to WKInterfaceController class's animateWithDuration method by extending the class with a method that chains together sequentially an arbitrary number of animation blocks. By combining concurrent and sequential animations we have at our disposal an unlimited number of ways to add complex (although often subtle) movement to our interface without having to deal with masses of complex code. The key here is to think about what we can do...