Pretty neat. Was a little confusing at first but after a little bit I figured it out. The main thing this could use is for human forces to actively attack and for you to have to fight them off, rather than just having them defend a few specific points. As it is, once you know where a target is you can just attack it and wait it out with no danger. Still was decently fun to clear everything out though. The use of the theme is alright, but isn't super unique mechanically.