Alien Swarm

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Alien Swarm
Alien Swarm Header.jpg
Alien Swarm header on Steam
Developer(s) Valve Corporation
Publisher(s) Valve Corporation
Composer(s) Mike Morasky
Engine Source
Platform(s) Microsoft Windows
Release July 19, 2010[1]
Genre(s) Top-down shooter
Mode(s) Single-player, multiplayer

Alien Swarm is a freeware multiplayer top-down shooter video game by Valve Corporation. It is a remake of the Alien Swarm mod for Unreal Tournament 2004, and it was developed by the original team, who were hired by Valve Corporation during the course of the development process.[1][2] A fan made sequel, Alien Swarm: Reactive Drop, was released in 2017.[3]


Alien Swarm is a top-down shooter set at a 60-degree angle. Four players can join a single co-operative game, the aim of which is to progress through science fiction-themed levels while eliminating waves of aliens. Players can choose from 40 different pieces of equipment, ranging from weapons like assault rifles to grenade launchers and offhand items like mines and healing beacons. The game includes persistent statistics, unlockable equipment, and achievements.[1]


The game is class-based, with players choosing from the roles of Officer, Special Weapons, Medic, and Tech. Each class has two selectable characters, with differences in abilities.

Grants a passive bonus to damage and damage resistance to nearby allies. He has access to the Vindicator, a class-restricted shotgun with an incendiary grenade launcher and has general all-around abilities. They are also capable of throwing extra amounts of explosive ordnance, and may find class-restricted ammo caches in the field for his Vindicator shotgun. The two playable characters are Sarge and Jaeger.
Special Weapons 
Brings raw damage to the table and starts out with a customized autogun with superior parameters, high magazine capacity, and auto-aiming ability. The Special Weapons gains access to a powerful minigun at a high enough level, and can pick up class-restricted ammo caches on the field. The two playable characters are Wildcat and Wolfe. Special weapons perks are often oriented towards pure damage output, with buffs like extra damage, piercing bullets, and faster reload.
Is the only class able to equip and deploy temporary healing beacons, and at a high enough level can use a medigun to selectively heal teammates and themselves. Both healing items counter parasitic infestations. The two playable characters are Faith and Bastille.
Carries a motion sensor, sets up sentry guns faster, welds doors faster, and is the only class capable of unlocking certain door panels or completing certain objectives by means of a hacking minigame. They also have access to a prototype assault rifle with auto-aiming capabilities and the ability to fire stun grenades. The two playable characters are Crash and Vegas.


Before the mission, players can change their character's loadouts and offhand items. They can also view both the mission information and the other players' loadouts. In single player, the player can modify all of their characters' loadouts. The mission involves all four players advancing in the same general direction, often with multiple objectives to accomplish. As they advance through the level, they will move through many different rooms and pass many different obstacles, from poison gas to reinforced doors. These obstacles are cleared through a variety of methods, from welding to shooting to hacking. Meanwhile, many aliens (known as Swarm) will attack the players from all sides. Swarm can spawn unpredictably, and will often attack the players with mobs of enemies, as described by their name. There are many different types of Swarm, with different behaviors and attack patterns. Players can fight Swarm using many tools, including weapons, explosives, or using environmental hazards (e.g. explosive barrels).

Players have four slots: a character slot (determining abilities, perks, and class-specific weapons), two weapons slots, and an offhand item slot. The character slot allows the player to choose between one of the eight characters, who each have certain buffs (i.e. extra damage, faster reload, etc.) and class-specific weapons and items (shotguns, autoguns, ammo crates, etc.). Players can equip two weapons in the weapon slots, as well as certain items or utilities. Offhand items (such as explosives, flares, and medkits) can be equipped in the offhand slot.


In the game's only official campaign, Jacob's Rest, a swarm of invasive aliens have taken over a colonized planet in December 2052. Marines deployed by the Bloodhound dropship arrive to search for survivors and, if need be, to destroy the colony to prevent the aliens from spreading. The task force kills a large number of not only "normal" Swarm aliens, but alien eggs, large tumor-like growths, parasites and other creatures. They soon find out that the colonists have all been killed by the alien infestation. The marines then guide a thermonuclear bomb (originally meant for excavation purposes) through the complex and activate its timer. They return to the drop ship before the bomb detonates.[citation needed]


Alien Swarm was announced in 2005, under the title of Alien Swarm: Infested, as a Source engine sequel to the original Unreal Tournament 2004 mod. However, by late 2007, the development blog had stopped updating, leaving its status uncertain. In July 2010 with the announcement of Alien Swarm, it was revealed that Valve had hired the team behind Alien Swarm, who had finished the mod between working on other Valve products such as Left 4 Dead and Portal 2.[4]

Software development kit[edit]

An Alien Swarm software development kit (SDK) including buildable source code was released alongside the game.[5][6] It is free to all users of Steam, rather than only to owners of existing Source games (as is the case with the 'mainline' Source SDK). This allows total conversion mods, which do not rely on content from other Valve games, to be free to all as well - a significant business decision that echoes the strategy of the Unreal Development Kit. The SDK and software license allows arbitrary usage and sharing but only for non-commercial purposes.[7]

The SDK tools include a tile-based level designing tool called TileGen, which allows level designers to prefabricate rooms and hallways that can be either arranged in a certain way or randomly arranged based on generation rules. The tool does not replace the Valve Hammer Editor, the use of which is still required before a map can be distributed.[8]


Aggregate score
Aggregator Score
Metacritic 77/100[9]
Review score
Publication Score
Destructoid 7.5/10[10]

Alien Swarm received mixed to positive reviews upon release, with a 77/100 on aggregate review score website Metacritic.[9][10]

Alien Swarm was a runner-up for Computer Games Magazine's 2004 "Best Mod" award, but lost to Red Orchestra: Combined Arms.[11]

See also[edit]


  1. ^ a b c "Alien Swarm". Steam. Valve Corporation. Archived from the original on August 8, 2010. Retrieved August 9, 2010. 
  2. ^ Walker, John (July 16, 2010). "Valve Announces New Game: Alien Swarm". Rock, Paper, Shotgun. Archived from the original on July 22, 2010. Retrieved July 27, 2010. 
  3. ^ Alien Swarm expanded by fan release Reactive Drop, out today, April 20, 2017, Peter Parrish,, Retrieved at 2017-07-06
  4. ^ Remo, Remo (July 16, 2010). "Valve To Freely Release Source-Powered Alien Swarm, Entire Codebase". Gamasutra. Archived from the original on July 19, 2010. Retrieved July 21, 2010. 
  5. ^ "Alien Swarm Game & Source SDK Release Coming Monday". Steam. Valve. July 16, 2010. Archived from the original on July 19, 2010. Retrieved August 9, 2010. 
  6. ^ Alien Swarm with complete code base releasing FREE on Steam on Gameranx (July 16, 2010)
  7. ^ AlienSwarm fork on "readme: You may, free of charge, download and use the SDK to develop a modified Valve game running on the Source engine. You may distribute your modified Valve game in source and object code form, but only for free."
  8. ^ "Swarm TileGen Distributing your map". Valve Developer Community. Valve. Retrieved January 8, 2012. 
  9. ^ a b "Alien Swarm for PC Reviews". Metacritic. Archived from the original on 2010-08-18. Retrieved April 13, 2014. 
  10. ^ a b Sterling, Jim (July 26, 2010). "Review: Alien Swarm". Destructoid. Retrieved April 13, 2014. 
  11. ^ Staff (March 2005). "The Best of 2004; The 14th Annual Computer Games Awards". Computer Games Magazine (172): 48–56. 

External links[edit]