Hm, I tried it, and it has potential, but the game is not really making use of that potential yet from my point of view. The main issue is that the enemies, despite looking different, do not act different. At least for the first three levels, I didn't play past that point as the core gameplay loop (kill the enemies) was rather time consuming than challenging.
That may sound harsh, but the good news is: By giving the enemies variety in behaviour, you can easily fix that in almost no time :-)
I like the controls, they are very good.
(by the way, in the grass level, I had just black background, looks like no texture was loaded or something like that).
So I hope this feedback helps you!