To really be the best at this game you need to learn how to balance army size and force with how much money is being made. Its alright to have a huge army but if that gets wiped out you need to be ready with enough money to make another wave or else you will get wiped out quickly.
Tip - For some odd reason they made the orks with a different army style. They can have many soldiers in one group, and they can have as many groups as long as they have towers up. The orks usually multiply to masses within a minute or two of the game so if you face off against them always get your commander and one group of soldiers. That should hold them off long enough to gain a bigger army.
The campaign mode is fun but only to a point. It can get a little boring, I prefer skirmishes or multi player matches. Well if anyone needs any tips or tricks to the game let me know and ill post it up! Thanks everyone, Death to the emperor!!
