This game is awesome! Total war chaos, this game is indeed unfair and you can be never sure how far will you get this time. I'd like to give it 5/5 but some bugs are very annoying, and it lacks many features like mute, quality settings and so on... 4/5 and I still play it even after completing achievements.
If your level is not high enough to pass a gate you can replay an earlier map to get exp you need. You can also look for a new gun that wasn't available to you when you passed it for the first time.
Read the instructions next time :P It says that the charge is given every time you kill 20 units. So it seems like you just allow your enemies to kill you too often...
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