To start - I'm assuming you know the basics of the game and maybe have even won at least once already, so I'm not going to explain most of the basic things. There's little point in attempting those achievement runs if you don't know those.

Also. I'm just writing my successful strategies and setups for the game. I'm not claiming they are the only ones viable, or the best, for that matter. If you can improve on them, great. If you can achieve the results differently, better, faster, etc., even better.

Another thing - when I say that a tower/upgrade/etc. is useless, I mean *I* have found it such for the particular challenge, not that I'm dissing your beloved frost towers that you can win any game with, k?

And I guess, I'll have to add this little changelog:
ver. 1.00 - Got the idea, made the first draft and published.
ver. 1.01 - corrected a few oversights and added the thank yous. ;)
ver. 1.02 - more oversights and reworked the basic setup into a table.

Joklng aside and with all that out of the way, let's get to it, shall we?

Why reset? Well, because otherwise your pool gets polluted with the towers you don't want. I've tried to do the solo ballista run with most towers unlocked and believe me, getting 5 card choice containing 4 towers and 1 possibly useful choice most of the waves got annoying very quickly.

The bad news continues. Resetting your tree clears your xp. That sucks. You can go and grind it all over again if you want, but... every time you try for an achievement? Heck no.

So, here's a method to quickly get your xp back:

Ok, so now you've got your xp points... what to spend them on? Here's the gist:

Unlocks:
Note, that you will be missing some of the treasury upgrades in some achievement runs. It's not that important, really. Better to have a smaller card pool than those 300'ish gold at the start of the run.

This is pretty much how you will, if you follow my strategy, do all the runs for achievements and also the longest part of this guide. It's not hard, only time consuming to set up and/or get reasonably lucky. You don't need the perfect single lane map with 3 huge killzones etc. Just... hope you don't get my luck of getting an average of 6-7 wave 5 splits before you got something to work with. Yes, the amount of salt I've produced while doing all the achievements was groriously large. ;-)

Mindset: I'm going for an achievement, not playing around.

General rule of thumb: Early split = restart. For example I restarted if I got a split before round 10-15 on a straight'ish map without possibilities of nice killzone after the split. I know you can try to go around the base and all that, but, in essence, you're here for the achievement, not the challenge of savig a crappy run and ballistas need their killzone.

Map requirements/building(Pics TBA, maybe):

Checkpoint 1: a single lane until you can set up a decent switchback killzone, at least 2x3 tiles.

Checkpoint 2: after the switchback as long a single lane as possible with a couple of ballistas along it to slow down the "run killers".

Checkpoint 3: after the first split, leave one path alone and continue to build out the other only, to ensure staggering of mobs getting to your killzone and to have as much time as you can before the boss reaches it. Try staggering the further splits, but don't forget to make the "boss" lane as long as possible.

Speaking of bosses though: Expand any "close lane" on waves 25, 35 and 45, since the boss always spawns from the furthest path away... Unless there are at least 2 entrances and you're expanding the furthest one. In that case it'll spawn from the second furthest lane. It took me a while to notice that. If you don't believe me, check it out the next time you play.

Tower placement and programming:

(To be honest, I might be juuuust slightly roleplaying those roles, but hey, it works. :-P)

I always put a "flower" of ballistas around the houses next to the tower and then try to only put them near other houses if possible. Ofc if your killzone is established at level 20+ you'll have to put some in between not to die, but I usually dismantle those early towers after I get to the killzone and start filling it.

Killzone:
Placement is simple - as many as possible, in places they can target as much road as possible, preferably on two parts of the road - start and end of killzone.

Killzone ballistas are usually divided into 3 categories - delayers, destroyers and cleaners. I build/reprogram them according to which mobs are the most dangerous at the moment.

Delayers: fastest/progress/progress. They're here to ensure that the bats, missiles and eyes don't just fly through and end your run and the rest stays in the killzone as long as possible. They will switch targets constantly.

Cleaners: most armor,health or shield/near death/near death. They will try their hardest to murder whatever is on the lowest health, starting with the toughest mobs and going down and helping with both the carriers and the cargo.

Destroyers: most health,armor or shield x2/progress they will target the biggest baddies that
are the closest to the tower , thus ensuring carriers disgorge their cargo as soon as possible.

Paths:
Before the killzone: Most health, armor or shield/progress/progress. They are here to slow down the biggest mobs/bosses so the killzone gets as much time as possible to deal with the rest of the chaff.
After the killzone: progress x3. They're here as a last ditch effort, but I don't usually place any that are not next to houses or in a really good spot, and only early, since if you've let things through your killzone you're done for anyway. If there are a few stragglers they should be dealt with the "utility" ballistas that are *cough*accepting donations*cough* from the houses and the flower around your base.


Card priorities:
wave 01 - 15: banditry -> lv1 of damage to X -> dots -> slow -> range -> +10% critical for tower type -> lv.2-3 of damage to X -> rest
wave 16 - 20: bleed! -> as above
wave 21 - 25: burn! -> university -> +5% critical to all towers (after unlocking university) -> as above
wave 26 - 35: poison! -> university -> dot upgrades -> university upgrades -> as above.
wave 35 - 44: dot upgrades -> university upgrades (until wave 40) -> as above

Also - try to grab the special dot cards - Creeping cough, slow cooker and eviscerate, they are all nice bonuses.


Let's address one more point here: leveling up individual towers vs using universities.
Depending on your playstyle you might be more inclined to level one individual tower to a supertower and laugh as it kills everything. Well... It might work for some of the achievements this guide covers. I don't know. Why? Because I'm more of a "tower spammer" and it shows in the strategies described in the guide.
Anyways - in these achievement runs you're going to be using 50+ ballistas every run. It's much more efficient to invest in universities and have them give buffs to all of them than to upgrade them individually. Or that's my oppinion anyway. I might be wrong, who knows? I'm currently having fun with checking if it's better to specialize the individual universities in 1 stat or is the equal spread better.

1. Reset your progress
   
2. Turn off the game
   
3. Go to Regedit and set your XP to around 10k... because why not?
   
4. launch the game
   
5. unlock the whole part of the progression tree to the left of the towers
   
6. unlock the tower you want an achievement for. Only the tower.
   
7. Play the run like you would a ballista only one and just unlock the other tower around wave 35'ish or even later if you wanna risk it and put one in somewhere it won't disrupt your build.
   
8. profit?

Rinse and repeat 12 times and voila, you're done. Easy, innit?

Ok, so you don't want to cheese the system. Or, like me, you find it boring to play the game in exxactly the same way 12 times in a row. Sure. Let's talk modifications to basic strategy for all the lovely machines of destruction this game lets you play around with, yes?
Some are easy. Some are omg-pls-end-my-suffering. And most are somewhat in between.
Also - most strategies won't differ all that much, since ballistas are the most versatile towers and they will still be used extensively in all of them.

I've put a notice of the ones that use mana just in case, so you need to get a mana building as an addition to everything else.

Reminder - my "ratings" are for the achievement run, not the "general" play, kay?

Mortar
The easiest of all of the runs. Mortars have range, aoe and decent fire rateand don't use mana. Plus they can apply all the dots. The downside? Errr... Help me out here? They seem to check all the boxes...
Strategy: use mortars instead of ballistas as the main damage dealers in your killzone and program them as you would the destroyer ballista. Nothing will go through.
Cards: yeah, get as many mortar ones as you can, but still remember to put all the dots on ballistas at least.

Tesla
Eehhhh... 'sok... you can set up a few in the killzone and use universities to kinda-sorta do what they did pre-nerf. They also can set up dots, but are kinda meh at it, they have aoe, but their range is small and they're inconvenient to set up unless you're lucky with the map.
Strategy: Uses mana. Set up 3 in a row, first one concentrating on shields, second on armor ant the last on health, but since you still need something for the later mobs/bosses' spawns, especially the last Oogie, so place them at the start of the killzone if possible and remember to place enough ballistas with slow nearby to allow them to take more than one shot at the enemies.
Cards: Get as many as you can, but prioritize Ballistas and univesities...

Sprayers
I'm putting both sprayers in one place, since the only difference is what kind of damage you'll need to focus your ballistas at (poison for flamethrower runs and burn for poison runs). They're pretty much identical in all other aspects.
Strategy: Uses mana. Killzone should still be mostly ballistas except for the corners, where you put sprayers at the beginning of a straight road and program them to progress x3 so they spray along the road and/or at end of the road and program them most health/armor/shield depending on the enemy composition for them to, mostly, constantly fire up the road. You can also put them before the killzone. For fun. Kinda underwhelming imo.
Cards: You could go for their respective uber dots, but it's only one type...they still won't kill the incompatible types, especially flamethrowers in the latest waves. Ballistas are more important.

Shredder
This one is a fun one. Not great, but fun. Sorry to say, but I kinda only used them as a novelty, since they specialise in the least important damage type - health.
Strategy: Just put a bunch in the killzone and enjoy the buzzing sound... Strategy remains as in the ballista solo. Meh.
Cards: Same as sprayers, pretty much...

Lookout
Don't really know, to be honest... I used them only once, for the achievement, as force multipliers for universities and with a standard ballista only strategy.
Strategy: Put them in the killzone and configure to most health, armor and/or shields, whichever you feel is the most problematic.
Cards: Get their upgrades, they do make a difference. Prioritize ballistas though, as they are the ones actually doing damage.

Frost Keep
Just don't... Really. No, I mean it. Oh okay. Sheesh... In theory they increase the max slow, but in my 3 attempts at the achievement I've never seen even one of those cards, so can't really say. Maybe it'd be good? I just don't like their incosistency between "projectile" animation and them actually hitting stuff, okay? :P
Strategy: Uses mana. Overlap as many as you can in the killzone and you can reduce the number of slowing ballistas.
Cards: yeah, no... range if there is nothing useful in the draw. Ballistas all the way.

Encampment
They're actually kinda fun to use. They can stack multiple mines on one square and they all explode individually so if there are 4 mines and mob dies after 2 the other 2 remain.
Strategy: You can use them anywhere... I used them both along the boss route for spreading/keeping up dots and in the killzone to augment burst damage, since they have enough time to stack mines upon mines upon mines there. They also have the haste limiter ability, but as with Frost Keep's max slow those cards never appeared in my run.
Cards: Worth it to get range and dot setters. Pretty standard otherwise.

Radar
Highly finicky boss killer "towers". Was fun to watch, but not very effective. Except boss waves. When set up to prioritize the boss, 5 of those annihilated the last boss before he even got 1/4th of the way to the tower. Not as useful for regular mobs, even though their damage is aoe, since they only have short firing time and if more than one target with the same priorities appears they tend to just scatter and do a bit damage to different targets and fly around a lot making them poor damage dealers and mediocre at best as dot setters. Their strafing runs are also pretty underwhelming if they come in across the road instead of along it. All in all not that useful.
Strategy: Set up a few as boss killers and just forget about them.concentrate on ballistas.
Cards: Range upgrades and dot for bosses, otherwise stick to ballistas.

Obelisk
Hoo boy. Fun, effective, but god they're expensive... They guzzle mana like it was going out of style and they cost a lot, too. They can stack up dots, and well at that, but why would you care when they just (literally) melt anything that approaches them. Not without other shortcomings, either. The range is low, no aoe and they required fiddling around with priorities when the new type of mob appeared, since you really can't make all that many of them. From my "calculations", every obelisk needs four mana banks to fire continuously. At level one. If you use them as your main damage source your map will be blue.
Strategy: Uses mana. So much you won't believe it until you see it. Set up a few on the front of the killzone and set your ballistas in front to mainly slow things down for maximum meltage and behind to pick up stragglers.
Cards: I dunno if I was swayed by the cool factor, but I've invested heavily in them, only picking up slow, dots and range for ballistas. But hey, it worked.

Particle Cannon
Better version of the radar - long range... and I do mean long range, boss/spawner mob killers, without aoe, but with consistent damage. They use mana, but not nearly as much as obelisks.
Strategy: Uses mana. Put them in the middle of the map, program them to target the toughest opponents and watch the carnage. You still need a good ballista killzone, though.
Cards: Definitely range, dots are also nice, since they apply a big chunk of them at onnce.

Reason why I was using regedit instead of grinding to respec the builds for the achievements.

TLDR: I value my time too highly to grind the slog of a beginning of the game 50 times from scratch just because someone decided that a respec should purge your xp. Sorry, not sorry. ;)
Btw - yes, I still love the game. :P

The explanation:
This game has a few features that are really fun when you start the game, but after 1-2 resets make a gigantic, pretty much gamebreaking in my oppinion, flaw:

1. resetting the unlock tree purges your xp, so you start literally from scratch
2. until you unlock both card frequency passives the game is frigging sloooooow and gets tedious really quickly
3. For the sake of achievement hunting and, arguably, normal play as well, meta progression bloats your deck to a state of unplayability.

Let me hit you with a comparison - it's like you played Slay the Spire or Monster Train, but you either only got basic cards, or you had to play with all the cards you've unlocked for all classes/races at once and you *had* to pick a card on every opportunity. Might be fun for a chaotic run or two, but that randomness gets old really quickly.

End of the rant. I promise. Really.


If you got here, congratulations, you've survived my rantiness and a big thanks for putting up with it.
I might spruce up this guide at some point, but it's been mostly written on impulse and to channel my stream of thought, so I might not. If it helps someone, good. ;)

Thank yous:
Ohm is Futile: for pointing out the tower health and +critical oversights! Also universities, but I'll still leave them as optional for the hardcore uni haters. :P
Liro Raériyo: for pointing out more oversights and possible optimisations.