I enjoyed the game. Launching ducks at enemy ships is fun!
I think the enemies are slightly to accurate: when they come in from outside the screen and I was changing my direction they hit me nearly every time. The spawnrate of ducks could also be improved, at times there where none around (or did I sent all ducks out and did not recall them?)
Lastly I'd suggest somekind of highscore mechanic.

I think the multiple plain design of the universe is looking beautiful.

Took me a while to find out how to get ducks at first, I like it, kinda has that arcade feel like sinistar, but with ducks. I do wish you maintained momentum when you let go of the keys, the fighting would be a lot more fun if you could spin and fire at someone chasing you while keeping your speed running away, as slowing to turn basically guarantees you'll be hit.

Smooth gameplay, great dynamic.
Neat art, I especially like how few layers of background create really nice feel of depth.
Fun arcade top-down shooter overall :D