Best I can tell game is 1 of 2 things: way too easy, or literally impossible without paying for upgrades. The energy system is stupidly unbalanced, esp when it comes to clan contributions. Haven't even played solo campaign for a while now as energy is spent on a pitiful amount of levels for ongoing events. Generally fun, but massive (MASSIVE) room for improvement, which is wholly dissapointing. Please fix energy and difficulty, and make clan activities more fun/worthwhile.