I couldn't see much of a point in this. It was just a bunch of flies that were coming towards you. You just clicked them and they went away. The idea itself is a bit too simplistic. You can have simple ideas, they just have to be done well. It just seems like something that's just lazily put together.
You need to make the flies look different. You could also have more weapons than just the lightning, although that is good. The overall designs need more detail. There should be more shading with everything. I've noticed that in a lot of good games.