Canyon
Opposite the exit, we see a bridge in the distance, across which the Alliance army is advancing. They're heading north to storm White Forest. We need to get ahead of them.
We descend into the canyon. Below are several antlion repellent devices. We move from one to the next, shooting the insects. When we reach the last device, protected by a fence, two guards will attack us from the mines.
The guards can throw cars, carts, and other large objects, so it's best to stay inside the fence. We use the Gravity Gun to pull explosive barrels and cylinders toward us and throw them at the bosses. Only then should we start wasting ammo. This is an unfavorable position for the enemies, so sooner or later we'll be able to destroy them.
Checkpoint
After defeating them, we approach the elevator. It doesn't work even after charging the generator. We climb the stairs and continue up the mountainside, dodging falling rocks along the way. There's a poisonous headcrab at the top, and one of the planks breaks underfoot. After avoiding all the traps, we jump onto the elevator roof, pull the bolt, and lift the hatch cover. The mechanism in the elevator cabin is blocked by a pickaxe; we knock it out with a gravity gun pulse. The elevator will fall, we board the passengers, and we head up together.
Up in the checkpoint room, no one is alive; all the rebels have been killed. We pick up a pulse rifle and some first aid kits along the way. We reach the observation deck; one panel is activated here, and there's a protective field nearby. (From the deck, we can see G-Man standing in the distance, on the near side of the destroyed bridge.) There's a car on the other side of the bridge; we need to reach it to outrun the Combine. We head there alone, with Alyx providing cover with a sniper rifle.
Descending the elevator shaft
Alyx will open a force field for us; we enter. We climb the stairs to a dead end. We push a massive cabinet against the side wall, finding a hatch leading into the elevator shaft behind it.
We jump down, break the boards beneath us, and fall further. We pass through the wooden wall. In the room, we are attacked by a zombie carrying headcrabs; we throw grenades at it.
We fall further down, finding ourselves in the cabin of a non-functioning elevator. We move along the open floor, fending off poisonous headcrabs. Here, Alyx will begin to assist us, shooting the monsters.
Lower Landings
We enter the door and find ourselves in a room with numerous barnacles on the ceiling. We destroy the monsters by feeding them explosive barrels and then detonating them at the right time. We walk across the dilapidated floor. Falling into the abyss is mortally dangerous.
In the narrow corridor, there is a fire trap that the zombies are trying to pass through. We turn the valve to shut off the gas and pass through the extinguished fire. We can go back, turn the gas back on, and fry the zombies pursuing us.
We go outside. A fast zombie will jump out of the dumpster. Ahead is a locked gate; to open it, we knock down the padlock. Around the corner are numerous zombies, but this is a fireable area; Alyx will destroy them all.
We crawl below, go down the stairs. We cross over to the bars. We fight poison zombies. Further on are barnacles and zombiebines. We climb up the stairs, collecting ammo and first aid kits.
Warehouse
Climb onto the warehouse roof. Use the Gravity Gun to remove the metal sheets to give Alyx a better view. Then, jump inside.
Enemies will start emerging from the side corridors. We shoot them down, leaving some for Alyx. There's a circular disc on the wall; we can use it to save ammo. After defeating them, we circle the perimeter, collecting ammo and first aid kits. The exit is behind one of the fences.
We enter the warehouse with shelves. We crawl under the first shelf, crawling between two rows. On the other side, we climb onto the upper shelves. We need to reach the upper balcony; there's a car lift in front of it. Lower the lift platform, place boxes or a refrigerator from the adjacent shelves on it. Raise the platform, and use the placed items to jump to the balcony.
Acid Pool
Exit through the ventilation. This is a pool with toxic waste; you can't go into the water; you need to jump across the islands. Numerous zombies will emerge from the water one by one. There are numerous regular barrels nearby that you can throw. If you haven't yet earned the "Bonebreaker" achievement, now's the time.
We'll make our way across the islands to the stairs, where a crowd of monsters will emerge. Fight our way through them. Further up is a chest containing infinite grenades; we can pelt the remaining enemies with them.
At the top, we'll crawl to the right under the metal structures and find ourselves in the adjacent acidic pool. There are far fewer islands here, so you'll have to create your own path. Use the Gravity Gun to attract large wooden spools, place them in the water in front of you, and then jump forward. Climb the stairs up the hill.
Broken Bridge
We climb up the green hill. There's a passage in the right wall of the bridge, through which we reach the bridge deck. Here we find the car we need – a yellow, half-wrecked Dodge Charger. We prepare to drive, but at that moment another portal flash occurs, and the central span of the bridge tilts to the other side.
We drive the car to the left wall, climb this wall, walk along it, and jump to the central span. The bridge is swaying like a seesaw, and we need to tilt it to the other side. To do this, use the gravity gun to push all the cars to the side that is currently higher. Some cars can simply be thrown down. The bridge should tilt in our direction.
We jump down the hill and return to the car. We get in and drive, jumping over the two resulting cliffs, and find ourselves on the road near the starting checkpoint.
We enter the side room, press the lever, this will open the doors for Alyx and the Vortigon. The alien lifts the gate on the road for us, and Alix and I can continue on .
Source: gamesisart.ru