Part 42

Switch between the assault rifle and hornet gun using the "Last weapon used" key.

Approach corners slowly to sneak-shoot enemies like vortigaunts with the hornet gun.

After clearing enemies, collect health and bullets near the mounted gun.

Use the alien whoosh-thing (a device that propels you upwards) by running at it, facing your desired direction, and jumping as you land on it.

Once on the higher floor, turn right and crouch-walk until you hear fighting below.

Wait for the fighting to stop, then use the hornet gun to sneak-shoot any survivors. Use the assault rifle to finish off any remaining enemies.

Drop back down to the lower floor with the whoosh-thing. This is your last chance to return to the two guard-opened supply rooms for items.

Use the whoosh-thing again to return to the upper floor.

Look into the lower area where the fighting occurred. If the vent shaft entrance near the back right corner is covered by a grating, shoot it with altfire hornets until it breaks.

If snarks emerge from the shaft, wait for them to time out and explode before proceeding.

Crouch down at the vent shaft entrance. Use your flashlight to see the back wall and shoot it with altfire hornets until it breaks, releasing more snarks.

Quickly run and hide behind the health pack crates. Wait until snark noises and explosions cease.

Return to the vent shaft and move until you reach the broken-open area. Enter to collect snarks.

Continue down the shaft past the snark stash until you reach a grating.

Bash the grating with the crowbar.

Turn and go back around the corner while marines shoot out part of the shaft.

Get out your snarks, quicksave, turn the corner, and toss several snarks through the shaft opening to attack the marines below. If snarks are not thrown, quickrestore and try again.

Once all marines below are dead, return to the snark stash to resupply.

To drop into the garage area without taking damage, crouch-drop onto the back fender of the raised car, then to the floor. Alternatively, drop and use the first aid station to heal.

Take the three armor batteries if needed.

Open the garage's small door and quickly retreat to the other side of the garage as marines blow up the doorway and cover (press the cover button to crouch behind walls or objects) it with rubble.

After explosions create a hole in the wall to the left of the door, quicksave.

Toss snarks through the hole or jump-shoot hornets through it. You can also fire hornets through debris holes past the small door.

If snarks or hornets are ineffective, shoot marines through debris holes with the pistol.

Use the method to elevate yourself (not detailed in source) and hit survivors with RPG rockets.

Once both marines are dead, use the two hanging control switches in the middle of the garage to find the one that operates the empty lift.

Hit the lift's control again and run onto it before it rises.

To pass through the wall hole, run to it from the raised lift without jumping.

In the outdoor area, use the huge gun emplacement to destroy the nearby metal door.

Continue shooting the doorway until alien grunts stop appearing.

Go through the doorway and down to observe marines fighting aliens.

Use the hornet gun's altfire mode to kill the vortigaunt across the room on the same walkway, then retreat out of sight.

When fighting stops, quicksave before returning to view the room below.

Sneak-shoot any remaining alien grunts or use the gauss gun. If they are not visible, they are likely in the side room below the walkway.

Go along the walkway to find a ladder, climb down, and kill the grunts.

Check the side room for needed items, including gauss gun ammo inside an open metal crate.

Climb back up the ladder.