Level 17 is about protecting Marcus from Oberon and the Empire. I've attempted it at least 6 or more times. I've tried several different routes, different research focuses, defenses, and strategies. I can't seem to get past it and I can't give up and go to the next level because it's locked until I complete 17. Any help would be very appreciated!

I'm not above using cheats and god modes. I usually would just drop it when I get frustrated and cheats aren't available. But I've really enjoyed all the other levels and I'd like to continue.