A few questions id like to ask b4 i buy

[Coyote]

How long (generally) is the campaign? Im hoping for at least 20+ hours of playtime.

How challenging and difficult is the game? Is there options for limitless amounts of difficulty where i can always be challenged even after mastering the game?

I cant just get away with spamming one type of defense and beat the game can i?
If so, im not very interested.
Orcs must die comes to mind with archer guardians lol... Game just gets boring as hell.

[Panterich]

It should be easy enough to get 20+ hours if you are unfamiliar with it.
Timed difficulty raises for about 5 hours in campaign.
There is also survival mode (90 minutes long by default) that challenges you to spend more time. Edit: 4 quite different survivals are available.

Campaign throws progressive objectives at you right away. Rushing them makes the game challenging. But you are never forced to do that. Spending time on preparations make it as easy as you could imagine. So mastering campaign makes it easy, although you can always challenge yourself by spending less time on preparations.

There is no true "endless" mode in this game (yet). However, even if Devs won`t make it, i`m sure there will be such mods (still kind of hard to implement that right now).

You can try surviving the end wave in demo without geting your hands dirty, to understand the difference between mindless spam and mastering the layout.
As the game is never endless, spamming does work. But it is ugly and you are not forced to do that.

All in all, if you preffer to play the game once, play the demo and consider waiting for another ~year. There is still a lot to be fixed, and Devs currently plan to do just that afaik.

[Jonny Sparta]

Campaign is very much at your own pace, i've easily but like 40 hours into mine and not finished.

Tons of sliders for difficulty are available for survival mode.

There are loads of different turrets and weapons that excel at different enemies.

[folk]

I think you'll easily get 20+ hours. I am somewhat of a completionist and I massively overbuild defenses and research everything. I've only done the campaign once, and I think it took me close to 30 hours.

Once they release the next major patch I will play it again on a higher difficulty.

I can't answer about the difficulty, I played on easy. It was certainly easy :-P

[Razguul]

If you don't mind LOTS of bugs buy it. Energy and repair mechanics are broken as well as save problems and crashes. Just look at the Known Issues FAQ with over 300 entries. Good luck.

[Immortal George]

If you do the campaign *properly you will need more than one tower type only for the very last wave of the campaign, but thats about it. I used the tier 1 sentry tower the entire brutal campaign without making a billion of them. (i say properly with an asterisk since you can get to the last map of each biome, not finish it, and it wont add those biome monsters to your attacks).

[Yumemirareru]

Can easily get 20+ hours out of it, but a fair bit of that might be spent waiting for research to complete.

[HellSlayer]

If you like unlocking stuff and basebuilding to make it pretty, you will most likelly will restart campaign to setup the main base the way you want. Its an easy 40h campaign if you enjoy it.

[RedPine]

There's at least one enemy that is completely immune to each damage type, so you can't rely on a single turret. You CAN rely on as few as two turrets, but I personally think it's more efficient to use at least three. Which three you prefer is up to theorycrafting, preference, and in which order you like to acquire the special resources.