Getting to the Blue Key Slot / Getting to the Red Key Slot

In the Barracks, enter the grate above the urinals to gain a tactical advantage against numerous Pig Cops and an Enforcer. Use Pipebombs to clear the room. Collect Steroids, Pistol Ammo, and Shotgun Shells from the left beds, and Chaingun Cannon Ammo from the right beds. Find two Large Medikits near the clock.

Locate SECRET 4: A switch on the counter opens a wall above a toilet stall, revealing a Portable Medikit.

Locate SECRET 5: Stand on the bed across from the TV; it acts as an elevator. Use it to access the next door, where a Jetpack and two Devastator Ammo are located.

In the Command Center, go left twice and follow the hallway. Fight the two Troopers and the Pig Cop. Activate the switches in the order O X X.

In the main Command Center area, defeat the four Pig Cops and two Troopers, using Pipebombs if necessary. Collect two Small Medikits near the wall.

Find a switch on the wall near the steel window; this opens access to the Entrance part of the level.

Use the Blue Key to bypass the Forcefield. To conserve resources, you can lure the Commander guarding the room to the Forcefield to deal splash damage to enemies inside.

After using the Blue Key, enter the room and use your Shrink Ray on the Commander.

Collect the Red Key, Shrink Ray Ammo, Pistol Ammo, a Large Medikit, and a Small Medikit from various locations within the room.

Return to the Command Center and activate the switches near the big door in the order X O X.

Go back to the Red Key Door Room and use the Red Key to open the Red Key Door.