Pretty cool little game. I think you had one of the better implementations of the theme. I played through a decent number of levels and enjoyed it. I think the art's a little bland, but it works. The sound design is great and really sets the tone. The only sound that didn't feel all that great was the turret, kinda lacked punch.
I didn't really have a problem with the movement once I got used to it. It kinda felt like the floaty-ness added an extra dynamic to the difficulty, where you had to be careful how you moved or you'd wind up in a trap or spending a while floating down from a high jump.
The main thing I didn't really get was the intro screen with all the power-ups. Were they supposed to be in game? Was I turning them on or off at the beginning? Didn't quite get it. Maybe they show up later (I probably only played 6 or 7 of the levels).
Either way, pretty solid effort. I think with some more inspired artwork and a few added mechanics, you could make a pretty neat little game that could be worth selling.