Awesome game! Also, very good for a 2006 flash game.
Mario's Castle first level took me like five tries before i completed it...
Anyways, i actually knew this game since i was much younger, but i didn't complete it because it was too hard for me.
Along with the Mario Boss, i didn't know how to defeat him until he died randomly after surviving most of his attacks.
(Does he die by surviving all of his attacks or hitting that giant mushroom he throws at you?)