I just had some issues with this game. I was pausing the game to check my score and when I unpaused the lily pads were invisible. There also seemed to be some other glitches with the pause button. Also the perfection star sounds like it should be an impossible badge.
I finally beat the "harder" difficulty took about 5 days of playtime maybe 4. Anyway to anyone still looking to win on "harder" or higher there is a trick to prevent zombie spawn. if there is a space away from your base you killed zombies at and want it to stay safe send someone to either recruit or scavenge. The next day just cancel the mission and send them out again. Also a lot of it is random luck in the beginning so figure out your win condition and what buildings you want for it. Also antivenom is a 10% increase to defense. not sure how much of this has been said before but I'll say it as a reminder.
The "harder" setting is so broken. I have come close to winning a few times but whenever I do the game starts mass killing my soldiers. "soldier jerk commits suicide" or "soldier stupid desserts" or even "rival gang killed soldier left in the open". Then you got the awful zombie build up. You end up more screwed if the zombies don't attack. They will mass numbers you can never hope to beat because the only defensive buildings are police stations and wall-mart stores. If I spend 2 days building a wall to keep zombies out it should add defense same with non defensive buildings. This game punishes you for reclaiming lands by adding more surface area but no gain to your overall defense. walls should add 2 per tile and any building other than defensive ones should add 2 as well so there is a point to owning extra lands other than making it harder.