Potential...
The basics are there, a moving turret, some enemies, now for the real deal
Some suggestions:
-Make the loading times real, because if you get a homing bullet you can click as many times as you like, and alwasys hit the ducks.
-Some variation in enemy's
-As someone else mentioned: make the graphics more gameworthy.
-Some sounds and music would do no harm
-Make the ducks come out of random directions rather then one corner.
That's about it, and good luck with programming!