Black Mesa (Industrial)
The latter part of Half-Life and Opposing Force drops the player in an industrial portion of Black Mesa. While there are laboratories, this area is more for processing. This portion includes Lambda Bunker.
This half of the facility is darker overall, compared to the laboratory region. Rooms, often made of dark concrete or metal, have very high ceilings. Crates and boxes litter these rooms, providing cover and an occasional maze-like design.
Tunnels are common for transport, both with the flat railcar and with the transit system featured at the start of the game. These are equally as dark, and are often littered with tight hallways and corridors to proceed down.
In the labs of Lambda bunker, equipment seems to be of higher tech than early in the game. Some labs seem adaptive, built out of existing storage rooms. It can be assumed that the entire area was used for storage of large items when the base was used by the military.
Since this area is darker overall than the first portion of Black Mesa, both by lights and by textures, the lighting difference can be used to a level designer's advantage, either for dramatic effect or for atmosphere.
Sounds are increased a bit in this area, with equipment noise being added to the mix. Again, the particular sound to use depends on what is around the player and what effect is desired.
Also beneficial is the appearance that the military has been there, accomplished either by leaving behind boxes and radios or by simple graffiti. A radio's presence also implies soldiers, causing the player to advance more cautiously.
Aliens are as common here as in the labs, but the types appearing have changed slightly. Vortigaunts still appear, as do headcrabs, but also appearing are Grunts and Alien Controllers. Barnacles are also relatively more common in this half of the facility. Most of the assassin encounters take place within the large, crate-filled rooms of this area, allowing them to jump from hiding place to hiding place easily.
The military has set up many blockades in an attempt to stop Gordon, using the darkness and design of the rooms to their advantage. Tripmines are placed where the player is likely to go, with some places housing high-power TNT tripmines that kill Gordon instantly. Almost all scientists or security guards in this area have been killed, either by aliens or soldiers. The few that survive in Lambda Bunker help Gordon get to Xen.