Defense Grid 2
65 Achievements
1,000
25-30h
Minimalist
Using only level 1 towers, Win any Chapter 4 (or later) mission.
10
2.75%
How to unlock the Minimalist achievement in Defense Grid 2 - Definitive Guide
I can confirm that if you mistakenly upgrade a tower to yellow it invalidates the achievement even if you sell it. You must use green level 1 towers all the way through.
EDIT: MastaGus has confirmed that you can build boost towers and use their upgrades and it will not negate the achievement.
Level- Mission 14
Difficulty- Easy
I did that mistake on my first run, when I sold one "misplaced" tower and achievement did not pop. Did second run with no tower selling and got this achievement.
The first mission of Chapter 4 is mission 12. Beat this or a later mission using towers without upgrading for this trophy to pop.
The easiest mission to obtain this trophy in is mission 13 called ‘Deep End’. Play in training mode on the easiest difficulty setting. Now build a missile tower on every available spot (do not upgrade any of them), sit back and watch the aliens get slaughtered until the mission ends.
This achievement requires that you do not upgrade any towers while winning a mission on maps 12-20. Most of the maps are amenable to this in Practice mode as they tend to be large and can afford to build tons of towers. For one approach that works, you can choose Practice mode on mission 12 (Incursion) and build only Gun and Concussion towers. Create a long convoluted path for the aliens to follow and fill all available spaces with towers. If you accidentally upgrade a tower, you can use the rewind feature to go back to the prior checkpoint and undo the upgrade without voiding the achievement. You need to win the mission to unlock this achievement, so you must have at least one core still on the map at the end of the game.