Defense Grid 2

the best way to get this is to load chapter 4 mission 13 deep end. Fill
all the slots up first then start upgrade the towers
you can get this and the untouchable achievement at the same time. Good luck!!!

I earned this by playing level 13 on Practice Mode on Easy Difficulty.
I placed 6 gun towers in the 6 tower spots in the big U that leads up to the core housing.
I upgraded these to level 3.
Around wave 16, the dropship aliens come in. So I used the command ship to raise the buttress up to the core housing.
I then put a gun tower on each of the inner spots and upgraded these to level 3. I did this with the Scatter Shot Augmentation at level 3, so you may need a few more towers, or I'd recommend using General Cai.
I ended with 40k resources left, so realistically you should just be able to spam the towers in every square. Note that upgrades tend to be better than more towers, however, so I would upgrade what you have first.

This should unlock at the score screen.

Edit: I apparently made a video that I never posted here. This shows my final tower placement.


Downvoters please comment.

I did this achievement on level 12 on easy difficulty . My tactic was to make the aliens go the long way round on the bottom part of the map by blocking of the short bend and also blocking the 2 middle squares, I then blocked off 3 of the 4 passages and only left the one closest to the cores so they have to snake round. At this point I started building guns along the path under the 3 pillars . If you keep upgrading all of your towers to level 3 you should have enough fire power to get you through the level but to be safe keep adding guns to the start of your snake path when ever you get spare resources.

I also did the Untouchable achievement at the same time so if you don't have that you should get it while doing this one.



I am not very good at explaining what I have done but I have included a video below to show you exactly how I did it which is much better.