I have completed all the levels in spider: SBM. And I have found some secrets in most of the levels. I thought there would be some story behind it which would be unfolded through the progression. Really shocked to find it ended without anything in the end. I don't understand what was the purpous in finding secrets in those levels.
If you really want to know and you have finished the game to it's full extent, heres a thread explaining it all http://forums.toucharcade.com/showthread.php?t=21744. Be warned, it's much more fun finding it out on your own.