1. Time for the final level.
2. You begin by losing your gravity gun, sadly taken away by Elite Overwatch.
3. A lengthy yet enjoyable cutscene follows, packed with double-betrayal and intrigue.
4. Blech! Take your hands off her you scoundrel!
5. Just when you think you have things figured out, the plot takes another twist.
6. You are now free to flirt with Alyx in the elevator.
7. Alyx's idea of a date is to take you to the Combine's dark fusion reactor. OK, back to the struggle for humanity.
8. Fill up at the combo station then enter the lift on the left.
9. You find Dr. Breen inside this bubble, awaiting transport to another universe. For someone in such a precarious position, he sure sounds full of himself.
10. Combine attack through this force field on the right.
11. Finish off the first wave of Combine then follow the ledge around this pillar to your right once it slides out of the way.
12. These three generators are at the top of a ramp. You need to work your way past them to the left, but you don't have to disable them, it just makes it easier to get by. You can also use the fusion cores to fend of any attacking overwatch.
13. Your goal is to reach the top of the device -- this is essentially a big upwardly-mobile jumping puzzle.
14. Work your way past the generators then leap onto the moving platform in this corner after defeating the Overwatch above.
15. Step off the platform once it reaches the next level then rough up some Elite Overwatch.
16. Follow the catwalk to the moving platform ahead. You'll know that you've reached milestones when you hear words of encouragement from Alyx, or discouraging words from Breen.
17. Step off the platform when it reaches this position. Fill up at the combo station then board another platform to the left after defeating another wave of Elite Overwatch.
18. Rise to the next level then follow the catwalk to this engagement. Continue left.
19. Step onto this next platform as Breen taunts, "Are you still with us, Dr. Freeman?"
20. Look up to witness the portal opening. Note the fusion cores to the left - these are your ammunition to stop Breen and end the game.
21. Toss a fusion core into the large orb of light. This triggers a ring of metal panels to rise.
22. It is these metal panels that you must destroy, reminiscent of the arcade game Star Castle. (Free online version here.) Geez, games have come a long way. Gunships will fire upon you while you whittle away at the panels, but you can largely ignore them if you work fast.
23. Once all the panels are destroyed, Alyx hops onto the catwalk. Breen has been stopped!
24. Time to go - but not before a few words from the G-Man.
25. Lastly, the credits. Game over.
26. Or is it? Watch till the end of the credits for a final good-bye from Lamar.