Half-Life 2: Episode 2



Hammer SDK

Production Time:


80 hours

Play Time:


5-10 minutes


Containment explores a classic game mechanic within the dystopian universe of Half-Life 2: Episode 2. Using the latest version of Hammer SDK, Containment explores a chronologically alternative path for Gordon Freeman through the Combine Citadel during the events of Episode 1. While separated from Alyx Vance, players encounter human-experimentation that leads to a zombie outbreak.

Unlike the traditional outbreak mythos, Containment uses the Chyrssalid mechanic from X-COM: UFO Defense. Within the dark confines of the Citadel, fast zombies carry an infection. When they attack a Combine soldier, the unit immediately transforms into a Zombine. When the Zombine unit dies, a new fast zombie emerges from the carcass.

In the shot below, a fast zombie approaches two Combine soldiers and swipes at one. In the blink of an eye, the infected soldier transmogrifies into a Zombine, and begins to attack the remaining Combine soldier.


Technical Aspect

Containment provided several scripting hurdles and provided an interesting microcosm of Half-Life 2 AI. The default AI packages of Combine soldiers, Zombines and fast zombies all interacted realistically, and in turn, created dynamic situations.

In the above shot, players use a control room to open a door on the far side of the room. During this time, a trio of fast zombies escape from their containment cells and overwhelm the Combine soldiers. The before and after shots show the fast zombies contained, and then the infection rapidly spreading.


Artistic Aspect

Working within the define confines of the Citadel created several design challenges. First, players are armed with only the normal gravity gun. This limits players to flinging debris at the Combine soldiers and zombie hordes, however, the Citadel is remarkably free of clutter and debris.

With no debris, gas canisters nor saw blades laying about, clever players steal grenades from Zombines, or capture a Manhack to use as a projectile or buzzsaw. This provides a short-term armament to the player, and encourages the player to make haste through the level.

In addition to the cleanliness of the Citadel, the overall structure emphasizes vertical spaces and imposing structures. Dark shadows and cool lighting contrast with the red glow of a Combine grenade, and the bloody shape of a zombie.


Scripting Explained

The infected fast zombie mechanic works with a complex prefab in Hammer SDK. 12 seperate entities comprise a single prefab, and all were hand-placed within the level. The nature of the spawning mechanic precluded using a standard entity maker.

The logic entities for the infected zombie prefab transform the Combine soldier into a Zombine only when hit with melee damage from a fast zombie. This damage filter prevents a stray bullet or grenade damage from triggering the transformation to a Zombine.

The Zombine transforms to a fast zombie upon death, leading to a humorous situation. After a Zombine uses a kamikaze grenade attack and explodes, a fast zombie emerges from the smoke and chases after it’s next target.


Additional Game Play Screenshots

Download Containment Documentation

Level Design Document

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