Deirdre has made some good points, and in addition I would suggest that maybe she is tired? Little babies get tired from stimulation, and while it might not seem like much to us, lying under a play gym for a baby is a big deal. It's like looking at a whole heap of different TV shows and hearing different music all at once, as your little one doesn't yet have the filtering abilities (and understanding of the world) that we do. All bubs are different, my first boy HATED his play gym and mobiles and dangling things and so we didn't use them at all, while our second loves them and has from an early age (2 weeks or so). He now plays and kicks for about 20 minutes at a time but then gets tired or bored, so what your girl is doing is perfectly normal. In my experience the frustration stage comes later, when they try to use their hands but can't. Then they creally crack it! Bubs also have favourite toys - our baby now loves a particular set of plastic keps but isn't keen on other stuff.