Wrote a first version of the AudioEngine. It is a Service which runs in the background (doesn't block the UI thread). Supports multiple music files and sound files. Supports sound playback speed (0.5 -> 2.0 for ball rolling acceleration). The engine is initialized in MainActivity and it constantly loops over the given music files, playback never ends. GameActivity rewritten as a base activity for all game screens, it contains the ServiceConnection that binds all the activities to the AudioEngine. Every Activity that extends from GameActivity has a variable called Audio which represents the AudioEngine Service. More "global variables" could be implemented in GameActivity, instead of using a singleton class for the purpose. Added 3 music files, props to soundcloud.com/qcl for letting me use them. Added one rolling sample, could be used for the ball sound.