It's called
Prune, and it's just been released! It's getting
great reviews, and if you have and iPhone or iPad you could do much worse for $4 USD. I do not, so I'm hoping for a port someday. In the meantime, all I can do for him is a bit of good word of mouth. ;)
EDIT:
Money quote from a review: "Prune is unlike anything I've played before, an original and strange game that's both soothing and absorbing. It's the kind of experience I want to pull out to show my friends instead of a game to kill a few minutes while I'm in riding the subway."