It's not a bad game by any stretch. It's fun and a good time-waster.
That said, the physics of the game is kind of off. Throwing one small stone will make it go as far as throwing three large ones. It's very noticeable in the later levels especially. Besides, it takes all the skill away from the game. Once you unlock the bigger stones, you never need to use the smaller ones again.
Also, what causes a death varies. Sometimes they die without being directly hit by anything, or they kill each other by bumping into each other. Unless they're lining their clothes with poisoned spikes, they shouldn't die that easily.
tl;dr It's rather enjoyable despite the physics issues. I'm looking forward to playing the sequel.
Best way to win the hard badge is to play through on easy, then set up and train five people up to 10 on all stats except maybe science and scavenging if you're in a hurry. After have those five leave, and start on seriously hard. You don't get to take equipment with you, but you do have all the human resources you'll need.
Get enough farms to get food to a net positive as fast as possible. The scavenger skill will let you empty buildings in one sweep, but huntable food is finite. While you're doing that, grab a hospital so your supersoldiers don't end up dying from disease. Do not lose any of the main five, or it becomes much harder to finish the game. Recruit a few people if you want, but they won't be useful for much other than scouting and draining your food supply. Sack a few allmarts and renovate them.
I recommend getting a lab and researching all the zombie killing things. They make defense much easier. If the doctor guy comes, tell him to piss off.
After it should be easy.
I wish we could "evict" people from the town. It's irritating if you bring in too many survivors- at a certain point, there's not enough farmland in the city to feed your people.
I use a few rhinos at the front with a bunny swarm behind it. Rhinos have as much defense as turtles but get a strong attack as well. Sprinkle a penguin in here and there if you have the food available – they kill off ghosts.
Some advice:
The four-cleric build from the first game doesn't work as well here. Don't bother with it.
I used two clerics, a barbarian, and a ranger. I had a strength-only cleric at front, the barbarian at the front, dexterity-only ranger at the back, and an intelligence-only cleric at the back. It works fairly well, though there may be a better strategy.
The barbarian has the best attack in the game, but it dies quickly without healing.
Undead levels are a nightmare without a strong smite attack from the int-cleric. With it, they're easy.
Rangers are very nice as all-rounders. With two-three turns of venom arrows they can take down a boss on their own if they're protected.
The Customer Badge is very much worth the cost. If you're fighting everything, you'll earn the price back again within 3 levels.
And yes, you should fight everything. If you don't, the higher levels will end up killing you off.
The rhino has about as much defense as the turtle, plus it has a strong attack. Once you unlock it you shouldn't need the turtle anymore unless your cultivation is too low
Four clerics works well, but there's another way.
Mage and rogue. Have the mage use the cosmic prison, then have the rogue use execute. Of course, you'll still want a cleric to serve as a meatshield / healer.
Honestly, you can win the entire game just by turning the sprinkler on in one floor, the gas on in another, and waiting. It just takes an absurdly long time.