I played 2 games: the first I played on normal easy and got the rank "pre-pre-beginner", and then I played on insane and got "very good"; the ranking is exactly very precise... still, the game was good.
How to beat last boss:
Buy:
(1) Lightning
(2) Duck
(3) 150k gun (shortshield or something like that)
Spam lightning until it is out, use duck, spam shortshield on top of him, he dies before he moves. Easy as pie :)
A while ago, u got the exp hat instead of the propeller hat for beating hat factory. That's how i got it the first time. But now it must be in a race with less than four players, and you have a (small) chance of getting it.
Pure yellowness ftw! Yellow spread primary and secondary owns, even for bosses the spread is ok because it hits them a lot.
I beat the game not knowing that bombs existed :P