Image: Sega

Aliens: Colonial Marines isn’t a great game. It was plagued by a troubled development, and Kotaku’s official review flatly called the game “awful.” However, a modder has discovered a critical spelling error in the game files that might be responsible.

In a post on ModDB linked in a thread on Resetera, Colonial Marines modder jamesdickinson963 claims that a spelling error in one of the game’s .ini files in the PC version of the game is responsible for some of the anemic decisions made by the iconic alien creatures that act as the primary antagonists of the game.

In the launch version of the game, which I myself attempted to play a couple years ago, the aliens often function like zombies. They get within shooting range, stand up on their hind legs, and approach you in a strange attempt to bludgeon the player to death. It is not very dynamic, and it is not all that exciting.

According to jamesdickinson963's post, the reason for the poor choices made by the AI are because a line crucial to the operation of enemy AI is misspelled. The line:

ClassRemapping=PecanGame.PecanSeqAct_AttachXenoToTether -> PecanGame.PecanSeqAct_AttachPawnToTeather


“Teather” here should be spelled as “tether,” as it is in many lines of code at the same location in the file, and the implications of the misspelling are significant.

An .ini file is a way of setting properties and values within a game. Since “tether” is spelled incorrectly in the .ini file, it means that the game is looking for a specific phrase in the file and not finding it. In this case, AI parameters are supposed to load from the file, but the misspelling means that nothing is being loaded.

Image: Sega


The consequence of nothing being loaded is that the “zone tether” function of the alien AI does not work. Based on some inferences made by looking at partial code, the initial post claims that the broken tether has hurt the AI’s ability to flank the player and to move away from other enemies. In other words, there are behaviors that would be based on the AI “reading” its location in its environment that just are not being moved.

That said, I loaded up and played through the opening level of Colonial Marines this morning, and I could not see a significant difference between the spelling correction and the spelling error that shipped with the game. That isn’t to say that there aren’t differences, though, because there are.

Here’s a gif of the unedited .ini file that you would have right out of the box:


As you can see, the creatures approach and just kind of stand there until my AI teammate shoots them enough that they die. There’s nothing special about this, and you can see even in this short clip why this game was not lauded for its awesome portrayal of the Alien cinematic universe.

Here is a gif of the edited .ini file in which I have spelled “tether” correctly:


You can see some immediate differences. The aliens do a little side-to-side shuffle to dodge bullets, they get behind objects, and they even do that leap at the end. This combat encounter looks a lot more dynamic and interesting, even if the creature does sort of lock up and just crouch there at the end before it dies.

However, I ran this mission several times in a row, completely exiting the game and altering the .ini file between each attempt, and I cannot be sure that the difference in spelling is making a huge difference in the combat AI. While that alien shuffle seems to happen fairly often in the “fixed” AI, the leap, some wall crawling, and hiding behind boxes all occurred fairly regularly and randomly in both the original and “fixed” AI configurations.

It’s clear that changing the spelling in the .ini file is doing something, but in my playthroughs of the first level, that something does not fundamentally correct all of the various problems with Colonial Marines. Aliens might hop around more, but they still do the zombie melee thing. They still clump up in a big anonymous horde to be mowed down with your rifle. It’s still a clunky game with slightly more active aliens now.


While this might be a massive improvement for later levels in the game, there’s no moment in the game’s opening level where this truly feels like the secret sauce that magically makes this game better than it was before.

Kotaku reached out to both Sega and Gearbox but did not receive comment in time for publication.