PAFCalc (Planted Aquarium Fertilizers Calculator) for Android is a useful utility that helps in calculations related to DIY fertilizers for planted aquariums. It has been completely written with the Android developer studio, which should ensure portability to tablets and smartphones. The app doesn't access any external functions on your device.
Pybik is an interactive, graphical, single player puzzle about the cube invented by Ernő Rubik. Besides the cube, the program can handle towers and bricks (non-cubic puzzles). Pybik also has solvers, pretty patterns, and a collection of various moves. The cube can be manipulated with the mouse or keyboard. You can change the colors or images on the faces of the cube.