The aim of this addon is to implement the cut fast headcrab NPC into the campaign while remaining as faithful as possible to Valve’s design principles. Careful consideration was given to the introduction, placement, and quantity of the NPC in order to integrate it as naturally as possible. It has its own introduction within the limits of the game’s maps. The NPC was generally not placed in areas meant for the introduction of other enemy NPCs, or in locations Valve intended to support exploration or puzzle solving rather than combat.

Close-quarters gameplay is sufficiently explored by nearly all of the game’s original headcrabs. The fast headcrab’s gameplay shines when it can be seen rushing at the player from some distance and closing the gap quickly. As much as established level geometry allowed, these NPCs are placed with this strength in mind. It is also entertaining to watch them skitter about from a safe vantage point or come crashing through physics props in pursuit of the player.

Valve meticulously tuned the ratio of combat to exploration in Half-Life: Alyx, and this addon does its best to respect these gameplay decisions. Therefore, the best was made of the relatively few areas that could support the fast headcrab while also following these principles. Restraint was used when placing these NPCs; the goal was to add them as an accent to the game, not have them overstay their welcome.

Of note, while the player will generally use greater amounts of ammunition with this NPC addon enabled, the game’s automatic resource balancing will accommodate this.