A.I. Arena #1: The Pilot Episode

Once upon a time, Chris Livingston’s Concerned had an extra feature called “To the Death“, where non-playable, AI-driven character (NPC) factions of Half-Life 2 were set against one another within Garry’s Mod, with Chris posting some pictures and hilariously narrating the results. Well, I always thought that was a good idea and I got Chris’ permission to bring it back a while ago, so I present to you:

AI Arena

The A.I. Arena will be a recurrent feature on Metrocop, a rip-off spiritual sequel to To the Death, working pretty much the same way: I envision scenarios, place the NPCs, let them duke it out without intervening while I literally fly around taking pictures, and then narrate the results. The narration itself will probably not be nearly as funny as Chris’, particularly while I’m explaining the pre-fight specifics, but I’ll try to make up to that by envisioning some crazy, strange scenarios and recording the results for posterity. And if you do want some of that Chris humor to brighten your life, I’d be remiss not to link you to his page, Screen Cuisine, which is a great site that will easily make you burst into laughter often.

And now that our sponsors have been properly credited, and keeping in mind that you can click the pictures to open them in full resolution, let’s move on to the main event!


This little slice of post-apocalyptic coastal heaven is New Little Odessa, or “N.L.O.” for short. For those of you who haven’t experienced the wonders of Half-Life 2, this is one of the remaining outposts of Human Resistance in the outskirts of the alien-controlled City Seventeen, led by a quirky character who goes by the name of…


… Odessa Cubbage. Colonel Odessa Cubbage. A boisterous man with a British accent and a moustache worthy of notice, Odessa is worshipped by the residents of N.L.O. and despised by pretty much everyone else, mainly due to his two-sided reputation: he takes credit for great accomplishments of rebellion against the Combine empire (such as the player’s own defeat of a deadly gunship in Half-Life 2), but he’s, in fact, little more than a royal coward. For the purpose of this fight, however, I equipped Odessa with the shotgun, a powerful close-range weapon, so he could lead his troops into battle – but from afar, i.e. from the ravaged second floor of N.L.O.’s main building, presumably away from harm, which would also make the shotgun somewhat ineffective. His cowardice is only defined by his scripting, however, so it’s possible his artificial intelligence, presumably the same as a regular rebel’s, might lead him to courageously jump into harm’s way.

Fighting alongside him is a character some visitors of the site might be familiar with…


Hercule Cubbage, the son of Colonel Odessa. Hercule isn’t an actual character within the standard game, but a creation of mine for my side-story webcomic. In the comic, he had exiled himself from the rebellious life of N.L.O.’s residents, fearful of ruining his father’s reputation, which he truly believes is real. For the purposes of this feature, I created a custom NPC with his appearance and the AI and aspects of regular rebels in Garry’s Mod, so, if you’re familiar with the game, you’ll know how he works: he’ll jump into battle to fight whatever threat may come, but he’s very vulnerable. Here, he’s equipped with the Combine standard issue pulse rifle, or AR2, the game’s equivalent of an assault rifle. It’s a deadly powerful and very accurate full-auto firearm, but NPCs tend to struggle with it when attacked at close-range.

Fighting alongside the Cubbages are the residents of N.L.O. the game spawns, bringing some strength in numbers to the mix. Since some are very specifically scripted, I occasionally removed them and spawned replacements, which should do just fine in fighting foes.


Horrendous and slimy but with a heart of gold, the Vortigaunt is an alien creature that, despite its appearance, is quite intellectual and a supporter of Humanity’s plight. Apparently despising both weaponry and clothing, the Vorts engage in battle using their natural predisposition for philosophical quotes and electric shock attacks, the latter of which easily bring down most foes the game throws at them, and the former being quite effective at entertaining guests during those headcrab-roasting dinners. This nude extraterrestrial powerhouse is definitely N.L.O.’s biggest asset and may tip the battle to the favour of the moustaches.


These two are the replacements I brought on for two scripted rebels of the game, which are too busy learning from Odessa the science of blowing up stuff to actually blow up stuff. The left guy’s a medic, which would come in handy if the game had his AI set on helping other rebels, but, as it stands, they’re usually too busy covering their own hide to help the guy being hit repeatedly in the groin – unless, of course, that guy is the player, in which case they’ll rush to your aid. Sycophants. The right lady’s a regular rebel, prepared to deal with any threat to the finest examples of human facial hair this side of the apocalypse. Both, like all other N.L.O. residents that are not Cubbages or an alien Aristoteles, are equipped with the game’s submachine gun, which has a steady rate of fire but is, unfortunately, somewhat inaccurate and prone to emptying the clip too quickly, forcing them to constantly reload. It can be an hindrance as often as a lifesaver.


These two fashionably-dressed refugees were spawned automatically by the game to keep watch on the coastline. I just moved them a little so they could be more immediate when facing the incoming threat (I’m getting there in a moment).


This guy was already in the game, so there’s not to say of him besides complimenting his fine goatee. He has a tendency to look upwards since, in-game, N.L.O. is expecting an aerial attack. Let’s hope that doesn’t affect his aim later on.


This lady was up in the makeshift watchtower surveying the skies. I thought that would be a bit of an unfair advantage to the enemy, so I moved her to the floor, but her fascination with the sky’s shade of blue remained unaffected.


This old guy is a specific case that gave me a bit of trouble. Turns out the game spawns an invincible refugee to lead you to Odessa Cubbage, just so you don’t run him over with a car – you know, “accidentally” – when playing the story. As such, I had to remove him and replace him with a carbon copy spawned manually, one that lacks the invulnerability of his scripted predecessor. He’ll do the trick. Or maybe not and he’ll die miserably useless, who knows? I do, that’s who, but you don’t yet. Just bear with me.

So, that’s one side of the fight – the downtrodden refugees of N.L.O. and their two dashing Brit leaders, numbering 7 followers, 1 green humanoid and 2 moustaches. If I haven’t bored you to death yet, you might be wondering who’s on the other side of this  brawl. Well…


Meet the Antlion Guard.

The Antlion Guard, or Myrmidont to his friends, is one of the most powerful foes in Half-Life 2, a towering brute with a perpetual itch in the right side of its face and scented genitals that swoon any of the smaller critters of its species that populate the coast and caves of the game’s world, not to mention a tendency to headbutt anything it doesn’t like, usually for instantaneously lethal results. Our predecessor, To the Death, actually pitched this awe-inspiring example of alien ugliness against the game’s toughest human NPCs more than once, and the results were not pretty: two out of three times the Antlion Guard won, and even in the third it caused some serious damage. Worse yet…


… he’s not alone.
These are the “critters” I just mentioned, the so-called antlions. They like long walks on the beach, underground tunnels and butchering humans to shreds, and dislike good vibrations (not the song, actual ground vibrations) and things that kill them, like bullets and electric beams coming out of two-fingered alien hands. They’re not exactly durable, but they make up for it with good disposition, sharp teeth, wings and pretty yellowish colorations. For this fight, the Guard’s brought an entourage of six regular antlions, to serve as cannon fodd… er, valuable allies in the ongoing struggle to rid the Earth of earthlings.


So, it’s a fight between 9 fragile, mostly poorly-equipped humans, accompanied by a friendly, all-powerful alien that can be killed by a single headbutt, and a pissed-off, extremely durable monster and its 6 tinier, weaker cousins. While the Antlion Guard has the obvious advantage of a surprisingly fast one-hit KO battering attack, the rebels of N.L.O. vastly outnumber it and their Vort friend can do some serious damage from afar, plus the terrain is uneven enough that they can safely hide from it while continuing to do damage. If they’re smart enough for that, of course – but it’s nine-years-old AI, ladies and gentlemen, so their plan of attack is usually as good as one made by a kid of that age.
Oh, and just to clarify: I won’t get involved in the fight. My job is only to take screencaps, follow the action and narrate what happened in the most entertaining wording I can come up with (which isn’t to say much). This is environment vs. environment, AI vs. AI, no-holds brawling between NPCs created by Valve Software, with no intervention from me. Also, the first few shots unfortunately display a server message due to me setting the AI on. I could edit that out, but I wanted unadultered footage from the grisly fight, so I hope you can look past that.

Okay! Fasten your seatbelts and pick up some popcorn, it’s time to set the AI loose.





As soon as they awake from their AI-disabled inactivity, the rebels react to the presence of the antlions, starting to shoot them, which, in turn, seems to attract their attention to the main building. At the same time, the Guard takes half a second to ponder whether to scratch its face or bash things with it…


… and settles on bashing, running straight for the biggest group of people around, some of which clearly are still trying to get their bearings.


But wait! It was a ruse! Just as the Guard stops, preparing to hit a seemingly unaware refugee with its head, he immediately turns around and starts shooting, while his similarly-dressed pal gives him some support fire. The other rebel, however, remains blissfully unaware of the impending carnage, his script forcing him to keep passively contemplating the skies, while I finally realize that his scripting won’t be interrupted. Until he’s dead, anyway, which is looking increasingly likely right now. As I’m focusing on the bigger threat and the antlions divided to conquer, the rest of the action remained off-screen, with the combined strength of moustaches and Vortigaunt deal with the weaker foes.


Surprisingly, the threatened refugee backs off while shooting the Guard, managing to dodge the oncoming headbutt, while the smartly-dressed rebel with the goatee ponders the meaning of life. By now, the sadly ignored little ‘lions have all been killed off-screen, after trying to kill the elder white-garbed refugee, turning their big butts on the major strength of the Vortigaunt and the Cubbages. Mental note: next time, set up some static cameras to better document all the happenings, you idiot.


The Antlion Guard, apparently shocked at the lack of flying corpses, seems to ponder for a moment whether to keep chasing its missed mark or switch targets, or perhaps he joined the goatee guy in staring blankly forward while bullets whiz by. The other refugee, feeling threatened, smartly runs away to an area where the Guard can’t chase him. This AI is like wine, you guys, it just gets better with age.


Our first human casualty! Alas, Goatee Guy. I knew him, dear reader. The rest of N.L.O. reacts, with bullets barely missing the Guard and hitting the nearby wall. A refugee has hidden in that barn, whereas his friend, safely away from the Guard, loses sight of the threat. In the meantime, the watchtower lady, under a similar scripting spell of Goatee Guy, turns a deaf ear to the murdering, prefering to wonder why the Sun is so big.


The Guard, getting bored of hunting down those two fashionably-dressed guys who keep evading him, moves on to an easier target, while they realize their hide-and-seek tactic worked and take the opportunity to shoot it square in the butt.


And another idiot bites the dust! The woman’s last sight is the same she had her entire life – the blue sky, calmly observing her death from above. Poetic. Perhaps stupid, but definitely poetic.


Smug from his recent killstreak, the Guard takes a second to contemplate its course of action, and I finally show you, in the midst of all the swift insanity that I can’t quite put into words, the deceased antlions, killed by the same teamwork that is now focusing on the bigger threat. The Vortigaunt’s beams miss their mark and hit a chest-high wall, always the AI aiming’s greatest enemy.


The combined might of N.L.O.’s finest keeps attacking, the Vortigaunt having descended from the building’s second floor to engage its enemy in proximity. Odessa, although actively trying to attack the threat instead of hiding away in the basement as usual, remains safely away from danger, more focused on protecting his curly facial hair than his men. The apple fell far from the tree, though, as Hercule is using his powerful AR2 as suppressing fire.


The Guard gets hit by the brunt force of the attacks, whereas the elder refugee safely dodged his foe and now awaits his opportunity to strike, or perhaps it’s just poor pathfinding preventing him from re-engaging the big bug.


The Guard, fed up with all the shooting and blasting, turns its sights on the nearby rebel, bending its neck in a fatal headbutt. Her friends, Hercule and the Vortigaunt, feel suddenly very uncomfortable with their plan of attack, as close proximity with an Antlion Guard, as you probably figured out by now, means close proximity with a bloody Antlion Guard.


Although my interest in doing narration of AI fighting is due to my respect for Valve’s work with the Half-Life 2 artificial intelligence and the fascinating fights it can create, even I have to admit that lining up neatly in front of a rampaging alien bull that can kill you with one headbutt is probably not the smartest course of action.


TIME PARADOX! Pre-The Adventures of Hercule Cubbage Hercule Cubbage goes down, ridiculously brushed aside by the Guard, who now turns to deal with its most dangerous foe, the Vortigaunt, while Odessa attempts to avenge his flesh and blood from the safety of his perch. However, it bears to note that the Guard is finally feeling the side effects of being repeatedly shot and shocked, as he begins to literally sweat blood, a sure sign that it’s nearly down and out. Will the Vortigaunt manage to bring its fearsome enemy down and emerge victorious, perhaps even taking the ballsack of its enemy as a worthy trophy prize, as seen once in Half-Life 2?


Nope. Alieno y alieno, face to face, the Guard wins every time. Odessa appears shell-shocked, possibly wondering if staying in the basement making useless radio calls as he usually does wouldn’t have been better than coming out to fight.


Completely ignoring the remaining Cubbage, the Guard moves on, while the medic discreetly reloads for another bout and the surviving hideaways keep up with the firing and attracting the attention of a deadly alien monster.


The lucky survivor of the Guard’s very first attack a while ago, confident that luck will strike twice, fearlessly keeps his peashooter firing steadily at the Guard’s face while it rushes headlong into the barn.


Well, that went well. Not so lucky now, eh? The Antlion, surprisingly, managed to not only fit neatly in the door, but actually aim straight for the refugee, killing him instantly. Now the question is: will its pathfinding let it get out of the barn, or is this an instant victory for the leftovers of these bug exterminators?


The surviving refugee clearly wants to test that theory, as he approaches the Guard, giving it the incentive of, at the very least, turning around to see what all the fuss is about.


Whoops! Turns out the game’s AI is not to be underestimated, as the Guard makes its way out and stares menacingly at the refugee and his tiny SMG.


And boom goes the dynamite!! The Guard literally lunges its foe forward, with the corpse hilariously rotating while it flies away.


The corpse doesn’t even have time to actually fall to the floor before the Antlion Guard makes another victim, as the elder refugee gets his white clothing smeared with blood. His own blood. All of it. He’s dead.


The Guard, not content with stopping the slaughtering, runs off in search of other victims, just as he’s hit with a damaging blast to the rear.


It’s Odessa Cubbage!! Well, I’ll be! The good Colonel finally gains the courage to get down there and avenge his entire outpost, bravely reloading his shotgun as the Guard rushes ahead.


But the Colonel dodges the fatal attack and keeps at it! The Guard looks positively as surprised as I am at this show of bravery, wit and, dare I say, competence!


And he keeps at it! The Colonel ingeniously uses the blue van’s positioning to circle the Guard and keep steadily firing! Will Colonel Odessa Cubbage, of all people, actually avenge his clan and be the one to


oh he’s dead.


But it turns out the fight is not quite over yet, as that one hiding medic we all forgot about turns up just as the Guard starts feeling bored. Perhaps fed up with the uselessness of his medical training in the battle, or perhaps believing he can still salvage a few usable organs out of all the corpses, he, too, starts enticing the Guard to attack with a string of tiny bullets.


The gigantic Antlion Guard roars menacingly at the attacking survivor, preparing to once again strike fear and death into its enemies…


… and then nothing happens.


Turns out I might’ve overestimated the pathfinding, as the medic hides away and the Guard gets distracted by all the oxygen surrounding it. For a second or two, I start to wonder if it’ll be a no-win situation, with both parties leaving one survivor completely distracted…


… but then the medic gets back to action! His gun might not be the most powerful, his aim might not even be truly excellent, but he seems to have the advantage of the terrain on his side!


The medic bravely goes forward while keeping his barrage of gunfire. Will the Guard still manage to circle back and corner its enemy, or will its weakened state be its undoing? Time is definitely not on its side, and the medic seems not intent on giving up just yet.


HOLY $#!&! ANTLION GUARD DOWN! ANTLION GUARD DOWN! The lone survivor of New Little Odessa actually manages to take down the mighty Myrmidont, thanks to some luck, AI ingenuity and a chest-high wall preventing the Guard from rushing to him and shoving him to death! It’s honestly mindblowingly unbelievable!


One of the most powerful enemies of the game, one that manages to take down the most powerful friendly NPCs in an open space, lays defeated, taken down by sheer numbers and the human and humanoid NPCs’ terrain advantage, even if two of the rebels were almost completely useless. It was the massacre we all expected, but the outcome was shocking – it’s death by pathfinding, people!


The anonymous medic stands triumphant amidst his fallen allies, unscathed and ready for another bout. One I will spare him for now, as he’s earned this victory. Against all odds and despite the death of his entire group, his sudden attack at the end after smartly avoiding harm all fight earned Humanity the victory in this first round of AI Arena. Hooray, hoomans!


The leader of N.L.O. lies motionless, which is usually the side-effect of being bashed to death by an impetuous alien headbutting machine. Ah, well, at least it sort of looks like he might have died killing all those antlions, even though he spent most of the match safely above the blood and gore of the gruesome brawl. Even in random, AI-derived death he takes all the credit.


Poor Hercule looks comical in his final pose. He fought bravely, died well, and looked ridiculous after death. Rest in peace, at least until I get around to finishing the third chapter of the comic series.

And that’s it for today! I had a lot of fun doing this but it took a while to do, so let me know if you’d like me to do more of these. If response is positive, I’ll definitely keep doing these, I have a few good ideas for match-ups. And remember, if you want to keep up with the site, subscribe by e-mail or RSS! See ya next time!

No exploding barrels were harmed in the making of this post. Disappointingly.



  1. Great job, I really enjoyed this. I have a question, though, do you know about half life 2’s squad mechanic? and if so did you use during this fight? if you plan on using combine soldiers or hunters you should really look into it; they tend to act smarter that way.

      • My mistake, I wasn’t referring to the squad mechanic of the citizens and the player I was referring to the squad mechanic of the npcs. It’s a mapping thing. Basically, it’s what makes the npcs work together. I don’t know if gmod sets it up by default, but there’s a couple console commands you can fire to set npcs into the same squad. The best way I can think of defining it is if npcs are in the same squad they’ll share information and use more advanced tactics. For example, soldiers will suppress, over-watch, and take turns attacking. And hunters will flank relative to allies and take turns charging.

    • I might! It’s just a lot of work for a small post, really – takes a full afternoon to do one, at least, and I couldn’t afford the time any longer, I’m afraid.

      That said, it’s hardly my idea in the first place so feel free to make your own! Just call it something else. 🙂

  2. NPC Kombat… Nice.

    I’ll credit you for the name. 🙂

    Thank you!

    Oh, and about the Squad Behavior thing… I don’t know what the Console code is, but I do know how to get the Rebels to behave smarter.
    Since in GMod 13, there is no limit to how many Rebels can be in your Squad (that I know of), you can use this to create more interesting fights. For example, like he said they share information in combat and use better strategies, but Medics also only heal anyone in the Player’s Squad (though they have to not be in the middle of shooting something and happen to be standing right next to them, unless it’s the player of course). So maybe what you could do is, before spawning any hostile NPCs, enable Join Player’s Squad and uncheck Ignore Player, make sure every Citizen/Rebel NPC is following you, then turn check Ignore Player again and put them all into position. NPC’s like the Vorties and Alyx’s can’t use this since they only follow the player via scripts from the map.

  3. Well, in case you’re interested at all, I have screenshotted the whole first battle, taking place in the first map of Follow Freeman! with a squad of Combine, and all my OC’s aside from Ronnie Dexture (who have a whopping 1500 HP). Since I’m that weird, I’ll give you teh brief nutshell version before I narrate the entire fight:
    — Nova was extremely agressive, charging headfirst at each rebel
    — Oddessa sniped. And appearantly mistook Pink for a man; as he intentionally shot several rounds between her legs.
    — Barney did the same with his AR2
    — Reggie became quit ethe punching bag
    — The single Antlion Guard didn’t last too long

Citizen, comment here

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