Pretty cool.
The boss gave me a bit of trouble with it's not-so-typical attacks but I pulled through (somehow, and only after lossing several lives to that stone-launch-from-behind thingy).
Seeing as this is a Beta might I suggest that you change the controlls?
As in "Please don't use X and Z because in europe a lot of people have something like a QWERTZ-keyboard - aka our Z is where your Y is. Doesb't make controlling exactely easier. ASDF or maybe even JKL or something should work on both kinds.
I like the graphics. Maybe because I like the whole "floaty islands" idea. If people tell you they don't like it they shouldn't be playing ti in the first place . . .
I guess you can do a lot more with colour if you'd want to.