Is Level 17 Level 12? It look to me harder, some expert please tell what exactly is Level 17 and onwards.

Hi nesmaster-- after level 16 the game loops back to level 9 I think (I can't remember exactly which level it loops back to). That is why the all levels category only goes to level 16. I don't believe the difficulty changes; although, I haven't tested it.

I think I remember Link_777 saying something about the level counter eventually resetting back to level 1 if you completed enough loops.