Getting the Red Key (4)

Secret Area: To the left of the very first metal archway in the hallway, find a secret door on the right wall. This leads to a passage with a door to the front of the building, containing a Chaingun Cannon and potential dropped items from Troopers.

Processing Plant: Enter the red door in the middle of the hallway. You'll emerge at the top of a ramp. A light switch near the door can illuminate the room.

Descent: You can go down the ramp normally. Alternatively, drop off the back of the ramp to find two boxes of Shotgun Shells.

Crane Puzzle: Observe the moving cranes picking up barrels. To proceed, go to a black-and-yellow striped pad. When a crane arrives, it will transport you to a hole in the wall with a conveyor belt and a Trooper.

Second Crane Ride: Repeat the crane ride on the black-and-yellow platform higher up. Be cautious of a tripbomb in your path; detonate it with an RPG or by luring a barrel or the Trooper's corpse through it.

Checkpoint Room: After being dropped off, you'll enter a small room with a glass window to your right. This room contains a Pig Cop.

Red Key: Kill the Pig Cop and enter the room. Inside, you'll find a Large Medikit and a small compartment containing the Red Key. There is also a switch that opens the door back into the main building.