Half-Life/Blast Pit

Approaching the silo
Break down the wooden barricades, and enter the station to the right. Pull the lever to call the elevator and collect supplies from the nearby room. When the elevator arrives, get on, and push the button to head down. When it reaches the lower floor, you can either take the train, or take the slower walkway around the side.

Near the end of the track, the train will speed up out of control, and crash just before the slime pit. To continue, clime to the top of the pipe, and enter them.

Follow the corridor until you reach the slime pit. Jump to the generator, and ride the elevator.

The silo
When entering or exiting the silo, you will see some explosive barrels. If they are struck, they will detonate and destroy part of the platform. In this case, you need to jump across or use other terrain to move along.

The silo itself will contain three tentacle-like creatures. They will try attacking wheverever they hear noise, but won't notice Freeman if he crouches while moving and doesn't attack. However, they can be quickly run past, and may also be stunned by grenades.

You will need to provide fuel, air, and water to activate the rocket to destroy the large enemy.

Oxygen and fuel
The oxygen and fuel supply is located two floors down the silo. Break the blockades, and run past before the tentacles attack. If the bridge to this section breaks, you can run across the piping that was under the bridge.

Look for and break open a floor grate. Climb down the ladder, and take a left. Follow the corridor until you reach a giant fan room. Head to the base.

Activate the fan by pressing the button, and quickly run back to the ladder. Stop just short of the fan blade, wait for one to pass, and climb out of the pit. Jump over the fan to fly up to the ceiling, which you will need to break open. Follow the vent until you reach the control room. Activate the oxygen and fuel pumps and return to the silo.

Power
The power supply is located past the lowest exit of the silo.

To reach the supply, follow the corridor to the end until you reach the elevator area. You should use the ladder to the right to reach the generator. While the elevator will malfunction, you can still call it to make it easier to jump to the ladder. Alternatively, you can simply jump into the slime pit below.

Past the scientist is a slightly cracked pipe with radiation. Crouch-jump onto the pipe to get past it without taking damage.

Press the switch to move the platform onto the other side, where you climb the ladder. Wait for the rogue platform to start moving away, and run towards the ladder to climb it. Turn on the first generator switch, climb over it, and press the second switch.

When you return to the silo, you will notice the water is electrified. To avoid taking damage, drag three nearby boxes onto the water, and use them to climb across.

Moving on
With the oxygen, fuel, and power ready, return to the silo control room, and press the button to oven-roast vegetables. Return to the base of the plant to get a new exit heading down. This will eventually lead to a water pit. In the room before this pit, you can collect a Magnum.

Walk along the pipes to the end. Turn the wheel to extend the pipe, and follow the pipe to where it collapses and drops you into the next chapter.

If you are low on health, the safest way to survive the collapsing pipe is to do a backwards jump as soon as the pipe breaks. Walk along the beam to the left, and try to jump down onto the supporting trusses. Look for any objects to jump on to further reduce falling damage.