Holy crap .. this is the hardest game on my iPhone I've ever played, 100000x harder than the popular TD games like Fieldrunners and Sentinel. I'm trying to beat Map 2, 4, 9, 11, and 12 on Medium and for me they're impossible. IMPOSSIBLE! Can someone who has beaten these give me some tips? I keep trying different strategies and failing. Been playing for hours now lol. Thanks.