Electroplankton is music game, in which you create music by touching things on the touch screen. In the US, it was released in limited number because it is not a mainstream game. Along with not being considered a mainstream game, it's also commonly considered not to be a game at all, but rather a toy, as there is no real objective, and there is no way to actually loose (in fact, its probably even less of a game that Brain Age is, seeing as that game actually features an objective/time limit/and score).