1. The slats slide away allowing you to enter the corridor ahead.
2. Overwatch attack, but they're no match for your Supercharged Gravity Gun.
3. Alyx gets to work at this console, exposing the core so you can get a good look at it. Follow her to the neighboring room where a combo station is found.
4. Alyx summons this lift; step inside and ride it down.
5. Energy balls can be found along the right wall. You'll need to activate a pair of sockets, one behind me in this shot and the other ahead/right. Stalkers will deactivate the sockets as you light them, so you'll need to first shoot your energy balls at the Stalkers and take them out.
6. Walk across the bridge once active, activate the third socket and walk across this second bridge.
7. Press this switch to rearrange the bridges.
8. Cross to the center of the structure and climb the ladder.
9. Follow the ledge to the doorway ahead/left.
10. More fodder for your Supercharged Gravity/God Gun.
11. Use the combo station after clearing out the room, then return outside and grab an energy ball for this socket. You'll need to shoot fast before the energy ball dissipates.
12. Manhacks, soliders and Overwatch attack. I recommend retreating to the corridor to funnel their assault. Here I fend of a manhack just after earning the Hot PotatOwned achievement for killing a Combine soldier with his own grenade.
13. Energizing the socket has activated this energy tether. You'll need to activate three of these to stabilize the core.
14. Heal at the combo station again then exit through this now-available corridor.
15. Pull this access panel off then carefully step inside.
16. Turn right, dodge the oncoming energy balls then exit through the opening on the left.
17. Ascend the ramp then hop onto the ledge on the right to continue around the corner ahead/left.
18. Remove this second panel.
19. Step through then battle more soldiers and Overwatch.
20. Grab the energy ball from this energy beam to disable the force field on the right.
21. Follow the bridge to this damaged ledge surrounding the core. Step onto the ledge and quickly sprint to the other bridge while the core is on the down-side of its oscillation.
22. Battle your way through this next corridor.
23. Activate the second energy tether with an energy ball from the beam to the left (deactivated already in this shot).
24. Don't exit the way you came. Instead, leave through this doorway to the right of the tether.
25. Ride a lift up to this next corridor where you'll battle more soldiers and Overwatch.
26. Find this combo station on the left as you near the exit.
27. Turn around to battle a couple more troops after exiting, then hop onto one of these rotating blades. Battle numerous manhacks -- just grab them and toss them into the blades or into the core itself.
28. Jump onto this balcony once it rotates into position.
29. Fight your way through this next corridor.
30. Remove this hatch and climb inside.
31. Jump off this ledge left of the fire.
32. Descend the ramp to another game of energy-bowling-ball. Dodge or jump the balls to reach the exit hatch at the far/left side of the alley.
33. More Overwatch attack as you exit.
34. Grab an energy ball from the alley and toss it into the socket.
35. Something goes wrong; the tether machinery moves into place but the tether never energizes. Jump into the pit on the right.
36. Enter this room beneath the subfloor and find three inactive energy beams. Grab energy balls from the opening in the ceiling and energize the three beams.
37. The third beam is a bit tricky. Energizing it activates the tether machinery and that's your ride out of here. Position yourself as I am here, near the tether machine/lift.
38. Energize the beam then quickly jump onto the lift before it rises out of reach.
39. Grab another energy ball from the alley and toss it into the socket to activate the third tether.
40. Take a gander at the core to find it peacefully contained.
41. Exit through here.
42. Return to Alyx and discover that the once-turncoat Judith is in trouble.
43. Alyx opens this door for you. Follow the corridor to the lift ahead.
44. Ride the lift down then follow the corridor a short distance until these Overwatch attack from behind. You'll be left defenseless as your Gravity Gun is no longer Supercharged.
45. After Alyx seals them off grab two of these roller mines for her to reprogram.
46. Hang back while the roller mines defeat this next wave of troops.
47. Once the area is clear, heal at this health station then follow Alyx into the train.
48. Alyx is relieved at the clean getaway until she discovers that the train is a Stalker transport.
49. After a short distance the train derails. Make your way through the car to Alyx. Use your Gravity Gun to pull this Stalker off of her.
50. Exit through this door then climb under the debris ahead to load the next level.