In the app Gamebanjo, I'm playing the tower defense game Tower of the Abyss and have reached the 4th map. I've been using fire towers to get through waves 3-7 (an air tower works for 1-2) but it seems that wave 8 is immune to fire. I've tried everything and have upgraded my towers pretty well. Is there a walkthrough for this game that I haven't been able to find or can anyone out there give me some tips?