Interacting with your Pixel
The pixel has 6 buttons on the back side: the 4 directional ones you use with your left hand, and A/B with your right. A is used for accepting/continuing, and B for declining/stopping. All apps by default will exit when you press B.
The badge boots into a launcher application, from which you can run all the apps you’ve installed with the up/down buttons. A starts the selected app.
You can remove any app that you install through the app store by pressing B in the launcher. System apps are protected from removal. Source code of these system apps can be found on Github.