I suppose you aimed to try and make it like the "good old" NES games. If so, you succeeded.
Though it has been mentioned, I say it again: Navigating those tight spaces like in lvl 15 and lvl 18 is just... well, "too" hard. I myself almost gave up at lvl 15 since I started to get frustrated, then passed with a little shout of "Yeah!", proceeded to beat some levels and at lvl 18 I was like this: "...you serious?"
Tried a couple of times, then thought "Gah, gonna take too long to master the movement". I'd almost say it takes more luck than skill at this point, but well, who knows.
For "average" player the difficulty is probably too much, ending in player quitting shortly. I'd say, make the movement of going up/down easier and I'd like the game better.
Side note: I have beaten some hard games like Demon's Souls before, so I wouldn't call myself average player. Just mentioning. :P
Rank: Jetpack Demigod, 38800 points. Made it to 18th of all time.