I enjoyed this a lot! It almost felt like a rhythm game :) Some good music that fits the rhythm of shooting the ducks would feel amazing I bet. The artstyle was also great, I really like this voxel modelling and I would like to try it myself one day as well. What did you make this in, if I may ask?
My only little criticism is that after a while it feels like it does not get any harder anymore, and I could go on forever (maybe I am wrong). Perhaps some ducks that take two shots would be interesting? To break the flow a bit. Or maybe ducks with different speeds? Just some random ideas :)
Great job, and really impressive you did this in only three hours!