The Game does not respect your time.

It Has a lot of good things ultimately ruined by bafflingly bad design choices, notably: no option to save at all except one to quit the game and pick back up later and no option to respec your tech tree in the campaign.

One of my all time favourites.

It's too grindy. The earlier missions are fun but the game is very much a "tryhard" game even on 50% difficulty. As far as I can tell how the rewards work, you're better off playing the earlier (i.e., easier) levels on a higher difficulty so you can unlock tech faster, so that you can actually survive in the later levels (I'm pretty sure I'm at the point of being softlocked on 50% difficulty because I started the campaign at 50% difficulty on account of being new to the game). It does go down to 25% so maybe I'll try that but we'll see, I'm kinda just done with it at this point (you can change the difficulty on any mission but the rewards scale with the difficulty I believe, so at 50% I'm getting half the tech points which ♥♥♥♥♥ you over later on it seems even if you stay at 50% the whole way).

But the big ♥♥♥♥ you is by the end of each level is basically a filter, so if you're not strong enough by then you just lose after spending at least an hour or so building up and fighting back the regular stream of zombies. Not to mention most missions are timed, so you have to hit a certain population level by a certain day (though, realistically it's the impending zombie horde which is the timer as if you don't have the population you won't have enough troops to fight off the horde, but apparently there's a second loss condition which is you didn't have a big enough population in time, and it always seems to be an asinine number of houses you need to build relative to the map size for that population number (it's as if every tile counts)). In practice when I've been able to fight off the final horde I've been able to hit that population number, but only barely (like, just hit it with one day left).

So it's just not really fun once you get beyond the first few missions (unless you're one of those people who's entire identity is tied to beating video games on hard mode).

Survival mode is a lot more fun in my opinion than the campaign.