In Chapter 1, Building a Clock App, we built an application from Kivy's standard components: layouts, text labels, and buttons. We were able to significantly customize the look of these components while retaining a very high level of abstraction—working with full-fledged widgets, as opposed to individual graphical primitives. This is convenient for certain types of applications but not always desirable, and as you will see shortly, the Kivy framework also provides tools to work with a lower level of abstraction: draw points and lines.

I believe that the best way to play with free-form graphics is by building a painting app. Our application, when complete, will be somewhat similar to the MS Paint application that comes bundled with the Windows OS.

Unlike Microsoft Paint, our Kivy Paint app will be fully cross-platform, including mobile devices running Android and iOS. Also, we will deliberately omit many features found in "real" software for image processing...