puzzle game for building molecules out of isolated atoms

 Atomix is a game designed for GNOME in which you have to build molecules,
 from simple inorganic to extremely complex organic ones, out of isolated
 atoms.
 .
 The first levels can be misleadingly easy, but added complexity always
 comes with the next level, so that several minutes (or even much more
 than that) can be spent on getting out of one single level.