Another application that looks simple but has some interesting code behind it.

The graphics power behind the application uses part of a custom 2D Games Framework I wrote in my free time.  It abstracts away the OpenGL API into an object oriented scene graph API that allows for very rapid game development.  For example to add an emoticon to the screen I simply create a new Sprite by specifying a drawable resource and a position and the framework takes care of loading the resource into graphics processor memory, creating all of the vertices and texture coordinates, and rendering that information using OpenGL ES.

The physics simulation is powered by the C++ version of Box2D which is built using the Android NDK and a custom JNI interface.  The interface provides all of the basic Box2D features to be available to my 2D game framework.  Some stand out features are Body and Shape creation, Force application, gravity controls, distance joints, pulley joints, prismatic joints, and gear joints.

I recently released a Holiday version of the application and plan to add a few more physics toys to it.