A standard calculator app with my own OpenGL-based UI. I did this as a little experiment to see how fully animated orientation changes and true 3D layouts could work. However I'm not really a user interface expert so this might be complete crap :)
I tried to make this as Material-Design-ish as possible, so the app looks pretty standard at first. However, rotate the screen or hit the view button and you should see the difference...
As the UI is full Open-GL and especially the shadow computations are quite expensive this might not run very well on slower devices.
This app is open source: https://github.com/fabmax/calculator