In my third try, I could get a 84% and pretty good score. It's just like real fly bashing, you just have to move slow, instead of fast, until you deliver the killing blow. And a little trick is to "slide" the weapon! as you hit. Aproach the flies from left side of the screen, and aim a little towards their left. And when you smash it, just pull a little bit righ. %84 in 33 seconds netted me a "very good" score.
Now, on to advanced training of fly-hunting. As you may already now, flies have eyes that can see all around (almost 180, with a blind spot towards back.) However, their sight is not "that" good towards up. They still see pretty well, but their responses to aproach from above (or directly below; however this is rare as they should be flying to make use of this angle) Thus our weapons work well when we aproach from above.
And using a plastic ruler I had very good results in the past, because it was transparent. Combining this fact with lowered visual senses towards above, I was able to clear my sisters room in short amount of time from the swarm of nasty flies, without waking her up.
Howeveri they have an additional defence that you have take into consideration, and it's those little hair all over their body. When you move a flat surface towards the fly in high speed, you create a ripple, or a wave which has a beginning point aproximately 2 cm ahead of the actual surface. When this "shockwave" hits the fly before the surface of your weapon, these little hairs vibrate and fly jumps to flight instinctively, without thinking. This is something like we do when we accidentally touch a hot surface.
Thus, many anti-fly weapons have small holes on them, to reduce the size and strength of surface.
Oops, I have to go. I will keep up my lecture on advanced fly hunting as if I have nothing better to do in the soon future.