[9-11] E2M1: The Installation

Near the start, find a room with a barricade. Go to the bridge leading to the water room. Walk halfway across the bridge, turn left, and jump into the water. Swim to the far corner of the area with the low ceiling, look up to find a tunnel, and swim up it to find Red Armor.

After obtaining the Gold Key, a door opens behind you. Jump into the water below this opening, follow the paths to a ramp, and climb it to enter a secret area.

Return to the Gold Key room. On opposite sides are two sets of bars. The set to your right (facing the back wall) has a small ledge at the top with a hard-to-see staircase beside it. Climb the stairs (you may need to jump) and jump onto the ledge. Walk through the wall to find +100 health.

Go to the room where you found the Silver Key. Descend the stairs into a room with a left path, a right path, and water in the center. Jump into the water and swim to a grate on the floor. Shoot or chop the grate (you may need to look down using the DELETE key) and descend into it. Follow the path to another grate; hit this grate to open secret 5, then follow the path to a room with items and a teleporter.

In the room reached via secret 4, if you hit the second grate, another hidden room will be accessible. If not, return and hit it. Inside, you will find Invincibility.

Locate the room with a large steel cage containing boxes. Activate the switch on one side of the cage to access a small elevator. Walk past the elevator and shoot the wall to your left to reveal a room containing Quad Damage.

Within the huge cage, once you are at the top, find a section with bars spaced farther apart, allowing you to squeeze through. Go to the bottom of the cage to find Yellow Armor.