Part 45

Activate the nearby ceiling turret (a type of automated weapon).

If the turret cannot see aliens, fire hornets (a type of projectile weapon) through the windows while crouched near the turret controls to hit them. The turret will fire at your hornets, keeping it alert.

After the first aliens are defeated, more will teleport in. The turret should eliminate some before being destroyed.

Use hornets to finish off remaining aliens, crouching for cover (a defensive position) to avoid return fire.

If firing hornets through windows is ineffective, crouch-walk to the doorway and fire hornets through the left end of the red railing. Avoid being seen by alien grunts.

Once all visible aliens are dealt with, turn off the turret if it's intact, then approach the control room windows cautiously, ready to shoot any remaining aliens.

Jump-crouch (a jumping and crouching maneuver) through a window or jump over the railing to enter the control room.

Locate and collect the gauss gun ammo from one of the wooden crates destroyed by hornets.

Be aware of a potential alien grunt behind the green crates to the left of the big ramp. Use the crossbow (a weapon) to sneak-shoot it if necessary.

Go down the big ramp, then turn right.

Use altfire (an alternate firing mode) hornets to destroy an explosive crate.

Fire regular hornets around the corner to hit vortigaunts (an enemy type) in the next room, aiming to kill the two in the open.

For the vortigaunt hiding near the bottom of some steps, either use hornets before it sees you or charge it with the shotgun or assault rifle (weapons).

Position yourself to use altfire hornets to shoot the glowing snark pod (an explosive container) over a hatch.

As soon as the pod breaks, run to the base of the big ramp and wait for the snark noises to stop.

Use altfire hornets to destroy the snark pod down the path to the left of the ramp.

Run to the hatch area where the first snark pod was and wait for these snarks to dissipate.

Proceed past where the snarks were to find a vine-covered side area with stairs. Bash through the vines.

Destroy the snark pod at the top of the stairs and quickly run to the safe hatch area. Wait for the snarks to time out.

Return up the stairs to access an upper walkway with a first aid station (a health replenishment item).

Go back down the stairs and bash through more vines to the left.

Use altfire hornets to break through vines past another snark pod, then use them to blow up a stack of explosive crates.

The explosion will open the pod; run to the safe spot at the hatch while waiting for the snarks.

Past the blown-up crates, find the last snark pod near a ramp leading down. Use altfire hornets and run to the hatch.

Return to the fenced-in side room near the top of the ramp. Push open the fence door.

Inside, find an RPG (a rocket launcher weapon) and a spare rocket next to a dead marine (an NPC (non-player character — anyone the game controls, not you)).

Use the hornet gun's altfire mode to kill the barnacle (a creature) hanging in a corner before collecting the snark pack (an item).

Go down the nearby ramp and look into the room beyond.

Use altfire hornets to destroy the rightmost wooden crate visible on the other side of the room.

This reveals the shoulder of an alien grunt behind the crates. Fire regular hornets slightly to the right of the crates so they swerve into the grunt.

When the grunt starts moving, strafe left partway up the ramp to avoid its line of sight. Continue using hornets to shoot it around the corner until it dies.

Crouch-walk past the left side of the two green crates, turn right, and approach the alien whoosh-thing (a device for traversal).

The other grunt is behind the large stack of green crates. Position yourself to see part of it.

Warning: Save your game (quicksave) before engaging the grunt behind the large stack of green crates. Blast it carefully with two RPG rockets. If you take damage, quickrestore (load the saved game) and try again after backing up.

As soon as the grunt dies, another grunt will teleport in near the bottom of the ramp. Edge over to sneak-shoot it to death with hornets.

Use the crowbar (a melee weapon) to bash open the remaining wooden crates in the room for supplies.

Use the whoosh-thing to reach a narrow ledge with snarks and a health pack.

Face the top of the green crate stack, run forward, and drop onto it to find the Crossbow (a weapon) and gauss gun ammo.

Drop to the floor and return to the fenced-in side room to resupply on RPG rockets.

Go back to the hatch found earlier.

Optionally, dive into the water near the hatch to find a dead marine with an armor battery (a protective item), two assault rifle clips (ammunition), and AR grenades (ammunition). Warning: The water contains many leech worms, so this is likely best skipped.

Use the wheel to open the hatch and climb down the ladder to reach section c3a1a.

Upon reaching section c3a1a, shoot the headcrab visible through the ladder with your pistol (a weapon).

After exiting the ladder, move through the red laser alert (a hazard).

Quickly move to a position where only the leg of the turret ahead is visible.

After the turret finishes shooting the headcrab near it, shoot the turret down with the pistol.