Latest favourite app chez nous is Osmos by Hemisphere games, a desperately pretty game with chillout sounds, available for Windows, Mac, Linux, Android and iThings.
The basic premise is that you are a sparkly blue “mote” that has to bump into and absorb smaller motes (tinged blue) and avoid being absorbed by larger motes (tinged red). Tap to one side of your mote-self to release a bit of energy propelling yourself in the other direction, but also shrinking yourself by the amount of energy released. If you’re lucky, you’ll pick up the mote of energy you released later – if you’re not, one of the other motes will get it and grow bigger at your expense. Furious tapping will most likely wind up in you shrinking in size and being easily gobbled by one of the other motes on screen; small numbers of strategic taps are more likely to result in you gobbling up the other motes and winning the game. Watch out for occasions where releasing enough energy to propel you towards a target shrinks you to the point that the target will wind up absorbing you instead of vice-versa!
To keep things fresh, different levels include features such as clever motes that can actively chase you or run away from you depending on their relative size, or attractive/repulsive forces that make it harder to move away from or towards certain types of mote.
The official site has a trailer video, free demos for Windows, Mac, Linux and Android (but sadly not iThings) and purchasing links if you’re convinced enough to go for it. It certainly gets a big thumbs up from all age groups in this house.
