Ok, where do i begin? 14 people got 0 days for their high score! 2 people got one! A whole bunch of people got 3, but considering u have a certain amount of fuel each level, they are likely hacking. BUT COME ON! ZERO DAYS IS IMPOSSIBLE AND SO IS TWO! Please look into this issue.
get the heli parts instead of the "cure" for the zombie plague, which is a fake, Recruit the survivor 'Bob Bila' from a farm/big farm nearby the heliport, And research electricity at the laboratory. There will be endless zombie hordes, not attacks, hordes, and you will need to protect your city. Well, i guess this is the end. Good luck, and have fun.
You need to find a helicopter (somewhere in your map) and reclaim it. Someone will blow it up, but its fine and meant to happen. It would say if you want to interrogate someone, and if you do he will die from the interrogators. But if you dont do that, there will likely be no consequences. Still with me? Good. After this you can speed up the progress by: get a survivor to read "Helicopter Repair for Morons". Instead of "A Cultural History of Zombies" in a scripted random event, which would produce a new self-acclaimed preacher. Which is bad. Very, Very bad.
(btw, this ends up as a guide to the heli ending, just a warning) For all you guys im going to tell you how impossible mode is like. Before I start this, i would like to say i like choosing the dog, because it could gives you 0.5 soldier points and 0.5 scavenger points (you really need food). First, you need to know about the endless zombie hordes coming to attack you, no matter what the percent chance they are coming. Second, you will have 25% happiness to take care of (less food brings down your happiness) and 25 food, going down 3 each day. By the way, the helicopter ending will help you in the impossible city because you get to send 5 people from any gamemode to any gamemode. That way you can send your highly leveled people to survive impossible. How do you get the helicopter ending you may say? Well, my hands are getting tired but ok. Wait, no, it says my content is too long, see you in the next comment!
My opinion: that kitty was not so bad. Well, maybe it was trying to make us frustrated, but it turned a normal robot that's power is literally just picking up stuff and walking into a FREAKING RAPID-FIRE LASER ROCKET-BOOSTING jumping PARKOUR ALIEN-DESTROYING 9000!!! But again, thats my opinion.