What controls wave difficulty on the headquarters map?

[Jeslis]

So - I'm not talking about easy/normal/hard/brutal or w/e they are called..

I mean more along the lines of.. You start a game on normal, and the first waves are zerglings... but over time they turn into ultralisks with hydra support (Using starcraft terms here, sorry!)

What causes that swap?

Can I prevent a difficulty spike if I keep my headquarters below level 5? or is it entirely time based... so I could keep is easier for longer if I teleport to the low threat maps faster and mine carbon/iron there instead of spending more time on the HQ map?

Any insight is appreciated.

[Miner 55]

Also wondering this

[cANe]

I'm pretty sure that collecting the different rare minerals increases it. After I got my first one, Titanium the difficulty in waves went insane. Several thousand enemies in a single wave and a ton of massive golem types.

It's kinda crazy since it went from being very easy to being insanely brutal, nothing in between

[Cresent]

it seems to be progress, and days, as well as if there are any nests around.

[Stu -1]

the nests trigger their own waves. and they can sometimes overlap with attack waves. i dont think they make the normal attack waves stronger though. i can confirm that up till day 60 i hadnt found any of the metals yet and i was only getting the basic zergling/ultralisk/hydra combo. although there was a ton of them at this stage. (excuse the starcraft reference XD) i will let you know if the next attack wave has golems etc

[Stu -1]

yup can confirm the very next attack wave had giant golems. giant mud men. and giant snails lobbing rocks from miles away. blasted right through me lol annoying lol because i had the tech to stop them i just got lazy with the easy waves and it was such an abrupt step up.

[Jeslis]

Originally posted by Stu -1:

yup can confirm the very next attack wave had giant golems. giant mud men. and giant snails lobbing rocks from miles away. blasted right through me lol annoying lol because i had the tech to stop them i just got lazy with the easy waves and it was such an abrupt step up.

So its likely to be some combination of day# + quest progress.. which kinda sucks as I'm definitely far behind in terms of # of days... and now Im scared to go get the materials >.>