Most of the maps can be beated simply spamming mages/warriors without even upgrading them. No color is the win option. Anyway most of the bugs has been corrected, increased the rating to 4/5.
I've increased the fast farmer skill...now I've 47,9.1 experience.... agree with everyone that says that it's bugged. Sounds more a beta than the third episode of a game... reduced my rating to 2/5