Well..
This is terrible. Glitches in the game, far too easy, sound ripped from L4D, boring, tedious, and all around un-fun. Fix the upgrading glitch so that the character doesn't run into the wall, change the sound, add in a few personal curve balls of your own, and expand the upgrade system a bit. As well, I haven't seen anyone talk about the glitch involving 'buying' new characters. It seems that, for me at least, I denied the first character, and the game froze, but the talking kept going. The scrolling still worked, and I could click the menus on, but that was it.