Pro Tip #3: The yellow radioactive battery inside the facility is what keeps all the power on which is why you should leave it for last. Besides turning off all the lights, it also locks the secure doors which will not be able to be openned through the terminal anymore (this same effect can be achieved by messing with the powerbox breakers) I should also mention that taking the battery will trigger an invisible eclipse mode. This means monsters will start spawning outside early and more often.
