The little bottle of BioGaia in the lower right shakes slightly, letting users know they can interact with it. The ad also plays on its own after 15 seconds, however.
As the level of BioGaia is increased upward with the slider, the baby's mood gradually improves, from miserable, to content, to possibly a little manic.
The sliding action subtly reinforces that, the more parents give their baby BioGaia, the happier the child will be. Or maybe not so subtly. Either way.
This is the expanded rollover state for the ad, because everyone loves ads that expand when you roll over them.