This guide covers what's good and what's not for units and skills. Also tells you how to beat Zone One on insane so SPOILER ALERT.
Random Tips Edit
Stack 40+ zava detectors and aries/lightbringers drop VERY COMMON.
Rare units drop only at higher levels. Some dude decompiled the game and found the drop rates but I can't find it anymore. Cant remember think it was Tesire and above...
This section pertains to units you can unlock with gold.
THE MUST HAVES (if your base doesn't have these then your base sucks):
Nyon Exist - for unknown reasons the only unit that prefers to focus bosses over their minions. Your only hope to beating Villalobos. Targetting speed upgrade increases FIRING RATE - must have! Other upgrades useless go spend you money on better things.
Chargors - Shoots little balls that boost firing rate of friendly units. Can boost other chargors. Cannot have range boosted. Damage increase upgrade MUST HAVE and should be maxed. Health upgrade useless. Range boost good to have but don't need to max it, just make sure all towers are in range for bosses.
Tech center - get zava detector and max out gold gen ASAP it's gonna be worth in long run.
THE GOOD TO HAVES (only cuz they help you beat Zone One insane):
Vira healer - one of your very limited options for healing your units. Max healing efficiency - everything else sucks. You'll need 4 of these for Zone One insane so might as well upgrade them early.
Neg voider - you'll need 4/5 of these for Zone One insane (depending on if you have three infinite fortresses). Upgrade Team Resistance so front of your base is 100% neg resistant. More than that is waste of gold. Other upgrades waste of gold.
ZAC Assimilator - Good substitute for defensive structure if you have Vira Ultima cuz it's got a shit ton of health; the fighters can tank even more enemies. However it's too expensive and fighters dont do enough dmg. If you want to beat Zone One insane asap dont bother with this at all.
THE GARBAGE YOU DON'T NEED:
Everything else that I didn't mention. Either because they suck so bad they barely work (looking at you vira savior), or cuz they are shit for damage, which is every turret that's not a Nyon Exist.
WHY AEGIS/TITAN BARRIER SUCKS: It doesn't have Healing Amplifier upgrade so you won't be able to heal it fast enough in Zone One insane against Villalobos. Use defensive walls and infinite fortresses instead. If you have vira ultimas then these are better than walls/fortresses cuz 40% dmg reduction lets them tank more although they dont protect as much of your base.
This section pertains to units you can only get as drops, but they are pretty easy to find.
THE MUST HAVES:
Defensive Wall: max Healing Amplifier. Terra Alloy good to max for Zone One insane but not must have. Wall and fortress are EQUALLY GOOD. Regen - good to have but there are better uses for your gold.
Infinite Fortress: IMPORTANT: Neg resistance on fortress - if you have three fortresses upgrade them + 4 neg voiders for 100% neg resistance. Otherwise don't get it at all and run 5 neg voiders. Regen - what did I just say about walls?
Santum Beacon: You'll need as many as possible for zone one insane (at least 6). Max out Sanctify - other upgrades meh.
Arcane wrath: the idea is that if you only have a small space to block off you can use this which also shoots bullets for extra dmg. Why it sucks? Shitty dmg, too small, no healing amplifier, not enough health.
Tesla - dmg sucks compared to Nyon Exist. Very expensive to upgrade use your gold for something else.
Rare Units Edit
This section pertains to the ultra rare units everyone wants but never get. No must haves cuz you won't find many.
GOOD TO HAVES:
Lightbringer/Aries - if you stack 40+ zava detectors on tech centers these drop like candy on Halloween. More DPS than Nyon Exist but they dont focus on bosses so don't use them to beat zone one insane. Regular enemies they are nice.
Vira Ultimate - 3 of these and you wont need any other healing unit for zone one insane. But most rare unit in the game gl finding them.
Thor - not tanky enough or enough dmg.
Darkness Barrier - No healing amplifier so you can't heal it fast. If you have vira ultimas they are ok but not any better than titan barriers.
Healing wave: don't have to max it. Enough so that it fully heals a wall/fortress that's very low on health. Whatever combination of healing amplifier and upgrade level of healing wave that lets you do this.
Guardian Orb/Decoy: very useful for protecting your base in general. Good to have for zone one insane boss but they get obliterated anyways so not necessary to max.
GOOD TO HAVE:
EMP: buys you time to heal up against bosses or when they rage. Although if the boss rages your base probably sucks. Not necessary against villalobos but very nice to have.
Oblivion: good damage, lots of health to tank for you. Zone one boss obliterates him but it still buys you time to heal up if needed. Very expensive to upgrade use your gold for something else since it's not necessary.
Aim here: Useless against bosses. Sometimes useful for regular enemies. Not expensive won't hurt to get it. Doesn't work sometimes.
Taunt: lets you farm better
Everything I didn't mention. Either shit dmg or barely works (literally).
Zone One Insane Edit
You don't need super rare units to accomplish this.
You must only use Nyon Exist for offense cuz they are the only tower that wont waste time hitting the minions.
THE FREAKIN OBVIOUS: Healing wave when necessary. Guardian orb/decoy whenever they up. Oblivion can tank too or put him behind boss for a bit of extra dmg (won't matter much though). EMP to buy you time to heal up or when he rages (shouldn't happen).
Chargor: dmg amplifier fully maxed.
Nyon Exist: Targetting speed maxed. NEED TO BE LVL 7.
Healers: Healing efficiency maxed.
Walls/fortresses: Health and healing amplifier maxed.
Neg voiders: Use 4 with three fortress or 5 if you don't have. Whatever to get the three defense structures in the front 100% neg resistance against darkness orbs.
Use this base 'nuff said. Zone One insane GG EASY.
Swag base if you wanna afk and win. Actually the thors may die cuz they are shit.