Part 20

When marines emerge from a doorway onto ramps, let the first be killed by a tripmine. Quickly double-barrel any others that follow. Staying crouched gives you an advantage as they won't immediately fire.

After the fighting stops, equip the .357 and sneak back to the doorway. Shoot any marines in or near the doorway in the head.

Move to the left edge of the doorway and look down the passage to the right. Shoot the computer bank on the left wall past a doorway with your pistol until it breaks, causing it to emit a continuous stream of fire.

Run down, jump over the fire stream, and position yourself against the wall next to it. If marines notice you and charge, run to the bottom of the nearby stairs and watch for grenades.

If grenades destroy a vent grating over the stairs, shoot the three headcrabs that drop down.

Return to the spot next to the fire stream. Quicksave and quickrestore to potentially trigger more marines to charge.

Jump over the flames and search the area to ensure all marines are defeated.

Jump back over the flames and break open crates in the area past the stairs to find ammo, tripmines, and grenades. Bash crates in the radio niche near the other side of the flames. Find an HEV recharger and a health pack past the large room with radio equipment and a lift.

ALTERNATIVE: After blowing up explosive crates upon entry, place a laser tripmine on the wall near the red-railed balcony where a marine would appear. If placed correctly, you can jump onto it, then to the balcony. Quickly shotgun-blast the marine around the corner, shoot the "eternal flame" machine, and use it to defeat other marines. This is trickier due to tripmine placement difficulty.

When ready to proceed, set three tripmines for approaching marines. Place the first tripmine on the wall to the right of the un-blown-up explosive crates near the area's start.

Go back up the ramps and through the doorway, then place the second tripmine on the wall to the right of the doorway.

Place the third tripmine on the wall under a red light to the right of that doorway (this one is less useful).

Use the lift's control panel to start its descent. Get on the lift with your assault rifle ready.

As the lift descends, look for houndeyes on the nearby walkway and kill them immediately to prevent them from detonating tripmines around the lift's base.

After the lift stops, move off it and wait for it to ascend.

Perform another houndeye check after the lift finishes ascending. Drop into the water and climb a ladder to the walkway.

Shoot explosive barrels visible down the walkway before proceeding that way. Wait near where the barrels were for more houndeyes to appear, then finish them off.

Go down the ramp and find the stairs. Go halfway down, turn left, and use your pistol to kill a distant headcrab.

Continue to the bottom of the stairs and stop just before the water.

While on the last stair not underwater, edge over to see the power generator machine in the watery area. Turn on your flashlight and shoot the rightmost of the two wooden crates next to the generator with your pistol. Once the crate breaks and the generator activates, return to where you shot the headcrab.

Use the first aid station on the right wall if needed. Enter the room with the power generator console.

Use the button panel to the left of the console to activate its green light. Turn around and time your run to pass the periodically firing electrical bolt.

You can use one of the two fans to return to the upper floor, but it is difficult. Alternatively, go back to the top of the stairs and along the walkway to the lift.

As you approach the lift, it will start lowering with two marines. Let one see you, then immediately run out of sight. He should hit a tripmine and blow himself and the other marine up.

SRC: It's likely only half the tripmines will detonate, and one or both marines may survive. Be ready to finish them quickly with the assault rifle. Alternatively, after the lift starts lowering, move back to see the nearest low-set tripmine but not the marines. Shooting that tripmine with your pistol as the lift stops lowering should kill both marines.

After the lift finishes ascending, use the button panel on the other side of its walkway to summon it. When it descends again, get on it.