up + down moves the ball into or away from the background.
i've long dreamed of a game where the player could whoosh off into the background whenever they wanted, so this was developed based on that impulse. the "floating ball" thing came from a variety of sources.... the smilin' sphere from earthbound, the smiley faces from midi maze, the stock image of a metal ball that is the source of metal mario's textures in super mario 64, the list goes on. videogames have a strangely storied history when it comes to floating balls.
