Part 13

When facing marines in a hallway, retreat to the top of the ramp. Wait for them to throw grenades and kill themselves, or shoot them as they come into view from the ramp's halfway point. Alternatively, go to the back of the lower floor and jump to get a better view of the upper floor.

After clearing the upper area, you can use the barnacle bridge as a shortcut, skipping some combat and supplies.

If not using the shortcut, jump onto the conveyor belt past the barnacle tongues. Run along it to a room containing assault rifle clips, a first aid station, and an HEV wall station.

Locate the lowest green crate in a large stack of crates. Jump from this crate to the highest green crate, using jump-crouches or big wooden crates for assistance.

Jump from the highest green crate to the high-up conveyor belt and run along it until you reach a room.

Quicksave (save your game progress) while still a distance from the room. Move into the room just enough for the marine on the other side to see you.

Quickly back up to the bend in the conveyor belt and wait for the marine to move next to the visible explosive barrels. Shoot the barrels to defeat the marine.

Warning: If the marine blows up the barrels, damages you with a grenade, or appears to replicate, quickrestore (reload your last save) and try again.

As an alternative, blow up the barrels as you approach the room, throw a grenade towards the marine's sandbag wall before they spot you, then charge them while they are dodging the blast.

Search the marine's side of the room for a first aid station and some ammo.

Look down to the lower floor to find several turrets and laser alarms.

After quicksaving, drop down to land next to the fire door's button. Go through the fire door and jump over the laser tripmine (a proximity-triggered explosive trap).

Warning: If anything goes wrong, quickrestore and try again.

Turn left past the tripmine and move forward. Look up to see a marine's legs on an upper walkway. Shoot their legs.

Wait for the marine to move towards stairs leading down to your floor. A barnacle's tongue should catch and eat them.

Trick two other marines into the same fate. Warning: If a marine reaches the stairs quickly after another is eaten, they may pass the barnacle, requiring you to shoot them.

Quickly run up the stairs while the last marine is distracted by the barnacle, or shoot the barnacle first.

Look for shotgun shells on a small green crate near a sandbag wall.

Go up more stairs and run along the walkway until you can turn left into a wide concrete corridor.

Continuing past this point on the walkway leads to a first aid station and assault rifle clips past a hard-to-see barnacle.

Go down the concrete corridor and across another barnacle-tongue bridge.

You will reach an upper walkway over an area where you previously killed marines. Go around this walkway and bash (destroy) crates to find an armor battery.

Locate stairs leading down to a lower walkway, which has stairs to the floor where the marines were.

Bash all crates on that floor for more items.

Find the large "SURFACE ACCESS" lift in the back and use its button to open it. Enter the lift and use its interior button to ascend to section c1a3b.

If the lift appears to jam after loading, crouch and move to break free of the glitch.

After the lift stops, crouch-hop onto the floor past it. Turn left and run for the corner with the first aid station on the wall. Staying left should allow you to avoid being seen by outside marines.

After quicksaving, go through the left side of the large doorway. Immediately turn left and run past two sets of wooden crates.

Turn right and run for the open door past another set of wooden crates. Crouching as you drop to the door, which is on slightly lower ground, may help.

As soon as you are through the door, climb down the ladder past it to reach section c1a3c.

Finish climbing down the ladder. Quickly bash crates in the area to find ammo and use the first aid and HEV stations to recharge.

Move to the vent access door to open it. Back up as a large explosion sends debris down the shaft past the door.

Ensure your assault rifle is ready. Quickly move through the vent access door and drop to the ledge on the right.

Turn and try to drop onto the broken fan before dropping to the metal walkway below.

Find the large opening in a wall next to the walkway and run down it to return to section c1a3.

When you reach the end of the shaft, quicksave before dropping to the narrow ledge below.

Move along the ledge and enter a vent shaft. Go forward until you reach an opening on your right.

Drop onto a green crate, then turn and crouch-walk under an unbreakable vent grating to access shotgun ammo.

Crouch-jump back onto the green crate.