āha
#

Lambda Core
# Enter the control room and push the button. Get on the freight elevator next to the truck and ride it down. In the room below, several Headcrabs and a Bullsquid await. Search the crates and climb up the ladder to the health dispenser. Go through the small metal door to the ladder.
# You'll enter hazardous materials bay A. There are several Human Assassins on the ground floor and two on the walkway above. There's a passage to the right blocked by crates. Break through and climb the stairs to the catwalk. Walk over to the passage on the left. Go down the stairs to access health and HEV power dispensers. Go up the stairs and follow the hallway to the elevator. Ride the elevator down.
# Open the door to hazardous materials bay B. Two Alien Grunts will be waiting. Move back to the hallway and take them out. Another will teleport in. Use the explosive canisters just next to it for an easier kill. One more will teleport into the storage bay. Once it's gone, climb up the ladder to the door and talk to the Scientist. He'll tell you about the Lambda reactor, then open the security door. Enter the reactor.
# Use the dispensers on the left, then ride the lift up to the second level. Turn right and enter the test firing lab. Pick up the EGON and the ammo from the shelf. You can open the firing chambers and kill the Headcrabs and Bullsquid beyond, but it isn't necessary. Exit the lab and go down the hall to the coolant system elevator.
# Turn right and follow the signs to the maintenance station. Talk to the guard and the Scientist. Get the ammo and use the dispensers. Now leave the station and return up the stairs. Follow the blue paint on the walls to coolant system 01. Fight your way to pump station 01, and flip the switch on the pump. Go back to the main area and follow the orange paint to coolant system 02. You'll need to jump over some debris and fight a number of guards on your way to the next pump station. The catwalk just before the pump station will collapse as an Alien Grunt teleports in. Jump the gap, avoid the Barnacles, and keep moving. Just before the pump station, turn the valve to shut off the steam pipe.
# Fight the Headcrabs in the pump room, then flip the switch. Get the HEV power canisters and make your way back to the main area.
# Follow the sign reading "auxiliary tank reactor access." In the tank room, a number of grunts will be teleporting in. You can either fight or just drop into the tank and avoid them. Follow the water to the reactor core. Turn both valves to flood the reactor. Climb the ladders, avoiding the energy beams and jumping the gaps, to reactor core D.
# Follow the hallway around, and then enter the supply cabinet for ammo and HEV power. Enter the elevator and climb the ladder to level B. Jump from the ladder to the broken door. Check the supply cabinet to the right, then go down the hall. Open to door to the security station on the right. Talk to the guard and use the health dispenser. Enter the hallway and fight the grunts and slaves that await you. At the far end of the hall are more grunts. Lure them into the hallway under the pipes, and then throw the steam valve. They'll fry quickly.
# Go down the hallway and turn the corner. At the end, you'll see a ladder. Climb down to level C. Jump onto the crates and over the fence. Jump off the left side of the pipe to get some supplies, then jump back again over the girder at the other side. Climb the ladder and head back up to level B.
# Enter the level B reactor core. What follows is a series of teleporters you must enter in the correct sequence. You enter the orange glowing portals and exit the green portals. As you enter the ports in the core, make sure you time your teleporting so that you land on the rotating platforms. Stand on the ledge of each port and look up to see when the platforms are in place. Following is the correct sequence for the teleporters:
# Jump into the teleporter at the base of the core. Jump into port 2. Duck under the pipe and jump into port 4. Jump into port 7. The various other ports will lead to some supply areas, so you may want to do a little exploring.
# Once you've jumped through port 7, you'll emerge in another teleportation room. Jump across the waste to the rotating platform in the center. You need to make it into the areas labeled "01" and "02." In each is a switch that will open half of the doorway to the teleporter. This is very difficult, so you may want to save your game each step of the way. The best method is to drop from the outer platforms to the middle platform when it is down, then drop to the inner platform. Going the other way, jump quickly from the inner platforms to the outer platforms and into the necessary areas, skipping the middle ring altogether. When the door is open, jump into the teleporter.
# You'll reach a new area on level B. Kill the Headcrabs and search the debris for HEV power. Then climb the ladder to level A. The Scientist will open the glass doors. Talk to him about what you need to do, gather the supplies, especially the jump module. Once you've taken the module, the Scientist will let you into the portal control room. Inside, use the dispensers and climb the ladder to the platform. Kill the flying beasts that enter while the portal is being opened. Once the technician gives you the go ahead, long jump (duck-jump) into the beam.