Half-Life: Opposing Force

Half-Life: Opposing Force (or OpFor) is a critically acclaimed expansion pack for the popular first-person shooter Half-Life, developed by Gearbox Software and released by Valve Software on October 31, 1999. The expansion's single-player mode features the same setting as the original, with the "twist" that the player is cast not as Gordon Freeman, but as Corporal Adrian Shephard, a United States Marine. Shephard is sent into the huge underground Black Mesa Research Facility on an undisclosed mission, but things go wrong and he finds himself fighting for survival against sinister government agents and monstrous aliens.

Plot

The action of Opposing Force cleverly interweaves with the original events of Half-Life, so that the player occasionally catches glimpses of Gordon Freeman, the player character from the original game, and visits some recognizable locations.

In the original Half-Life, a "resonance cascade" opens an extra-dimensional rift, allowing an alien army to invade Black Mesa. The surviving scientists and security guards at the facility struggle to escape. Responding swiftly, the United States military initiates a massive "clean-up" operation to eradicate the alien presence at Black Mesa as well as "silence" any witnesses. As the game begins, Shephard is part of this operation. After his transport aircraft is shot down and he is cut off from the rest of his unit, the clean-up mission is abandoned and Shephard joins forces with the scattered survivors seeking escape.

As the tide of the furious battle begins to favor the alien army, Shephard realizes the military forces have been ordered to pull out. The Black Ops forces (seen only briefly in the first game) are acting independently of the marines, and intend to destroy the entire complex with a thermonuclear warhead. Shephard deactivates the bomb but later sees the G-Man reactivating it. After defeating a monstrous boss alien, Shephard finds himself back in an Osprey-like transport with the G-Man. The nuke at Black Mesa detonates and the G-Man detains Shephard someplace where he can do no harm and cannot be harmed, pending further evaluation...

Weapons

Opposing Force includes many weapons, some of which were also available in the original Half-Life. The weapons may also be used in the game's multiplayer mode.

• Combat knife: The base mêlée weapon Shephard starts with. It delivers only modest damage, but is very fast and effective against headcrabs or already damaged aliens.

• Monkey wrench: Another crude mêlée weapon suitable for bashing crates and enemies alike. Alternate fire lets the player slowly prepare for a more powerful strike.

• Barnacle (alien weapon): The Black Mesa scientists were able to "tame" this Xen creature that normally adheres to ceilings. Its ability to latch onto distant organic targets (including enemies) using its long tongue makes it useful as a grappling hook allowing the player to scale heights and cross otherwise impassable gaps. Primary fire shoots out the tongue and pulls the player towards whatever it sticks to, alt-fire stops it from retracting its tongue, allowing you to swing around.

• Pistol (GLOCK 17 by default, Beretta M9 pistol with the High Definition pack): The first and simplest ranged weapon. Has good accuracy but low damage that makes it more useful on weak targets such as headcrabs or laser trip mines. Unlike most other ranged weapons, this pistol is effective underwater. Primary fire is accurate with every shot; secondary fire is faster but less accurate.

• Desert Eagle: This powerful pistol is similar to the magnum from Half-Life but has less recoil and a faster rate of fire. Alt-fire activates its laser sight, which increases its accuracy and power but reduces its firing rate.

• Submachine gun (HK MP5/A3 by default, Colt M4/M203 assault rifle with the High Definition pack): Its fast rate of fire compensates for its poor damage and accuracy. Secondary fire launches a grenade that detonates on impact. Uses the same ammunition as the pistol.

• Shotgun (SPAS-12): Does high damage at close range, but its broad fire cone makes it weak at a distance. It can be reloaded one shell at a time, but is slow to fully reload. Its secondary fire shoots two rounds simultaneously.

• RPG launcher (ATGM-4000 RPG Launcher): Does a large amount of explosive splash damage. Secondary fire toggles a laser that guides the RPG to its target. The player can only hold one rocket at a time along with five in reserve.

• Hand grenade: As in Half-Life, this frag grenade explodes a few seconds after being thrown.

• Laser trip mine: A high-explosive Claymore-like mine that can be attached to walls. It is set off either by damaging the mine or by breaking the laser tripwire it emits.

• Satchel charge: A high-explosive that can be thrown a short distance and detonated when the player presses fire. Secondary fire allows the player to place several satchels and detonate them simultaneously.

• Snarks (alien weapon): Small, aggressive alien creatures that quickly pursue their target, pestering and biting, until finally exploding after several seconds (or if shot). If they cannot locate a hostile target, they will turn on the player that set them loose. Can be used, for example, to draw enemies out from their cover.

• M249 squad automatic weapon (SAW): This machine gun is very effective at cutting down groups of enemies, but empties quickly and has a long reload time. Its powerful recoil makes it difficult to aim; crouching while firing can help alleviate this.

• M40A1 sniper rifle: A standard of FPS games, this weapon accurately delivers powerful single rounds, which hit instantly, unlike Half-Life<i>'s crossbow bolts. Alt-fire activates the variable-power scope.

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