Getting the Blue Key (8)

You'll start by opening a door and immediately facing a Trooper. Take care of him, then as you exit that first door, immediately look to your left. There's a small compartment you can open. Inside, you'll find some Night Vision Goggles and a Shotgun. Grab 'em!

This next area is called the 'hub' because you can eventually access most of the level from here. You'll see three distinct paths forward, marked on the wall as 02, 03, and 04. We're going to focus on 04 for now.

There are also some vents on the wall. If you go into these, you can find Shotgun Shells, a Large Medikit, and Atomic Health. All these vents eventually lead to a Devastator, so they're worth checking out if you need supplies.

Now, head towards the path labeled '04'. This one doesn't require any special key to enter, which is convenient. This path leads to the washroom.

As soon as you open the door to the washroom, be ready! Two Commanders will attack you right away. It's a good idea to quickly back out of the doorway to avoid taking too much damage. Once they're dealt with, head further into the washroom.

Look around the urinals – you'll find some Enforcers there. Also, keep an eye out in the stalls, as there are Troopers hiding in some of them. Near the urinals, you can find a Portable Medikit and some Devastator Ammo.

Check the counter near the mirror; you'll find some Steroids there, which can really help you move faster.

Now, let's find that Blue Key. Go to the urinals: the farthest left one has an RPG and a Trooper. The second urinal has a grate you can enter, which leads to some Devastator Ammo via a bathroom vent. The third urinal has a Trooper and, importantly, the Blue Key you're looking for! The fourth urinal has a Laser Tripbomb. Make sure you grab the key from the third urinal.