 - more tutorials
 - better music.
 - 'Text' items should cache their surface, even with effects, for one frame
   to the next.
 - when destroying networks in a row, add combo effects to pts
 - create a boom sprite for the dynamite block.
 - Add a plane passing with random messages.
 - Keep the list of all the updated rect and only update those.
 - go through the XXX/TODOs, move magic numbers as constants...
 - make sure the original few lines are not self-triggering.
