TLDR: As Engineer, finish charging the teleporter with zero monsters remaining on the stage

'Engineer: Zero Sum' is an achievement that can be easily obtained by anyone who has unlocked the 'Engineer.'

Unlocking the Engineer is extremely simple;
Finish 30 Levels.
and that's literally it.

Upon unlocking the Engineer, you will be met with a screen similar to this;

(ignore my lack of skins lol)

Today, we are focusing on the 'Utility' section. The bubble shield will automatically be equipped, the utility itself isn't horrible, though it can be a little situational. For example, if you are pushed out of your bubble, you cannot shoot through it from the outside. Many players much prefer the 'Thermal Harpoon' utility.

Simply put, to unlock the 'Thermal Harpoons' all you have to do is:
Finish charging the teleporter with zero monsters remaining on the stage.

Further into this guide, I will explain some cool tricks and tips for making this seemingly easy challenge, a little easier and less tedious.

Thermal Harpoons offer a much more mobile and offensive play-style than the bubble shield does.


(image provided by: Risk of Rain 2 Fandom Wiki Page)

The Bubble Shield, while still good, can be situational, as previously mentioned. The bubble cannot be shot through from the outside, so if you lose control of the bubble, an enemy can hide inside, practically disarming you. The bubble shield is a much more defensive style, forcing you to uphold in a small confined area. While this can be good, since enemies are unable to shoot through the shield, enemies can still attack from the ground ( ex. Magma Worm ) as well as enemies can just walk through the shield..


(image provided by: Risk of Rain 2 Fandom Wiki Page)

THE PROS OF BUBBLE SHIELD

- Provides complete protection from incoming projectiles for a limited time

- Allows turrets a more safe area to be placed in

- Can save your life if under heavy fire

THE CONS OF BUBBLE SHIELD

- Forces a more stationary style of game-play, which can prove difficult in higher difficulties.

- Enemies can still attack from the ground

- Enemies can walk through the shield, forcing you out

- Unable to shoot through bubble from outside if forced out.

The Thermal Harpoons offer a more offensive, mobile play-style. Thermal Harpoons can be used from a distance, making them a great choice for killing those pesky flying enemies, as well as keeping a safe distance between you and enemies. The Thermal Harpoons deal a decent chunk of damage and can be a great choice if you're looking for a damage boost! Though, you will be less protected from enemies, but this shouldn't be a problem if you get your hands on some Bustling Fungus.

THE PROS OF THERMAL HARPOONS

- Allows you to deal damage from a safe distance, especially against flying enemies like wisps.

- Provides a significant damage bonus, with each harpoon dealing 500% damage.

- Great synergy with items that summon additional projectiles

- Allows you to keep up with your turret's DPS

THE CONS OF THERMAL HARPOONS

- Requires you to be mobile and potentially less protected.

- Demands more active aiming to lock onto targets effectively.

At the end of the day, they are both great options.
The Bubble Shield can be used for players who want a more defensive and static play-style,
while the Thermal Harpoons can be used for players who want a more offensive and mobile play-style.

Now, if you're like me, when I first saw this achievement I shrugged it off and thought it'd be easy.. turns out, it was... just a lot more tedious than I originally thought. So let me pass down the wisdom I had to learn the hard way down to anyone who might be trying this achievement for the first time.

First, I'm going to start with the single best piece of information I learned:
If the boss is alive and the teleporter is at 99%, ENEMIES DO NOT SPAWN ANYMORE. (unless you're fighting Beetle Queen, since she spawns Beetle Guards, essentially soft-locking)




Which means, the best way to complete this achievement is to start the teleporting process, do NOT kill the boss, and wait till it hits 99%. At this point you should kill every enemy except for the boss, do a lap or 2 around the map killing any wandering enemies, then finally, kill the boss. This is the single easiest way of completing this achievement and will save you the multiple retries of forgetting a single wisp 9,000 miles across the map. Make sure to utilize your turrets OUTSIDE of the boss area, they can mow down the hordes of enemies that will spawn. Do not spawn them in the boss area or they could kill the boss and ruin your chances.



Good luck to any newbies and enjoy the Harpoons.
Thanks for reading,
galv <3