suggestion
I had a big problem once the spiders started showing up. The bottom halves of the dead zombie-worms acted as meat shields. So while the spiders were hurling crap at me, I could not hit them. I would also recommend changing the scenery up a bit, maybe throwing in some bonus rounds, something to break up the monotony. It has the potential to be a lot of fun...I will be looking back at it as you improve it. :)