Some very poor choices.
I see a lot of people bitching about how hard this game is, and I've got to say I agree. I got to the end pretty quickly, but the difficulty just didn't make the game fun. Difficult and fun games give you a challenge, but one that betters you with time. Instead, this game throws as many random enemies and crap at you, as fast as it can. Difficulty factor is not a problem in games, that is if it's done right. This game, WAS NOT.
The graphics are good, the sound is decent, and the game would be fun, if it was difficult, like say, the megaman series. Instead it's so goddamn impossible that, while it's beatable, it's not fun in any way. Many people who play this game can't get past the first or second level, and I have to say the difficulty gets infuriating.
Honestly after a certain point it's just not even worth playing. A way too difficult side scroller that tries to throw in extras to compensate for everything else.