Hello! Nice shooter!
There are a few things that could be improved.
The movement is not restricted to the play area. I was able to "rescue" the "good" baby and just wait for the next one outside of the play area without being shot...
I got confused by the scores... there are two, one I got that represented how many babies I had rescued, but what the other one stands for? Is that the amount of damage taken? Would the player die?
The re-use of the sprites is ok, but I would change the gray babies... I understood that they weren't the ones I was looking for and could be shot, but I still don't know if that's right or wrong... lol
Keep it up!
Cheers!