I know we are all sick of this tower defense games, but this actually does seem like a pay quality tower defense game for free. While its clearly buy non-native speakers, the translations are, by that standard, pretty good.
I only see 4 towers, slow, rifle (for fast monsters), a poorly described tower the nitch for which I havent figured out, and a missile tower which is both the longest range and hardest hitting tower. Not a great variety, but the maps seem really varied -- fieldrunners open placement style on some parts of the map, limited placements on certain terrain, destructible obstacles for cash, and nicely varied maps. No IAP that I have seen yet.
Difficulty seems (preliminarily) hardish. Even the initial maps are not cake.
I clearly wouldnt pay $3.99 for it, nor even .99 given how many of these games I have. That said, it seems like a pretty good download at free if you like TD.