1. Destroy all the rotating turrets.

2. Health and energy refills.

3. Proceed through this green-lit doorway.

4. Chell advises to use the tricorder's Trace Gas View Mode to spot where the gas is coming from. Save time and ignore vents that aren't releasing gas.

5. Use your phaser to seal the venting gas.

6. Now, let's work on that secret. Use your phaser to push each of these symbols into the wall. The order you hit them is unimportant.

7. You'll hear this door opening in the room behind you.

8. Step on the symbols in the floor corresponding to the wall panels. The order is important here -- mimic the symbols on the wall from top to bottom.

9. Your reward is this staff. Its potent secondary fire stuns your oponent with its touch.

10. Exit the area through this door.

11. Activate your tricorder's Bioscan View Mode and avoid the bio scanners.

12. "Use" the Security Panel to deactivate the Bio Scanners and the force field.

13. Activate your tricorder's Structural Integrity View Mode and blast away this cracked wall. Retrieve the 28th Golden Starship.

14. Head around the back corner for a secret area and 50 Idryllium.

15. Jump onto these tubes and carefully time your jump so the rising tube seen in the back lifts you to within jumping distance of the door area. Pass through the green-lit door.

16. Shoot the ceiling turret. Jump on one of the tubes then jump off as indicated.

17. "Use" the wall under these pipes to reveal the 29th Golden Starship.

18. Jump down and make your way to "use" the security panel, activating the elevators.

19. Crawl along the ledge above the Security Panel to another secret area and more Idryllium.

20. Hop onto one of the ascending elevators then leap onto this ledge where another secret area and more Idryllium awaits.

21. Take an elevator back down, jump onto the ledge above the previous secret area and jump onto this pipe. Take the ramp to the green door and exit.

22. "Use" the Security Panel to call the elevator visible in the background. Hop on.

23. Leap onto the roof of the habitrail. At the end is Golden Starship number 30.

24. Slide off the right side and head for this floating light.

25. You'll be treated to another secret area complete with pint-size Xenomorphs!

26. Next, go up this ladder and through the green doors.

27. Jumpin' Jack Flash it's a Gas!

28. Use your tricorder to modulate the Idryll Gas Controls.

29. New vents rise from the floor. Your tricorder's Trace Gas View Mode will save you time -- only use your phaser where gas is venting. The vents will lower when all the dangerous vents are sealed.

30. Yea another energy bridge. Wait for the whole thing to go dark, then jump when this panel lights up. You can then bunny-hop to the other side in one quick dash.

31. "Use" the Security Panel and Chell reports, "Munro, whatever you did just opened the second door in the main hall."

32. Stand on this round area.

33. Look up. Use your tricorder's Structural Integrity View mode to eye your target. Blast away. The panel you're standing on will raise you to a secret area with the 31st Golden Starship.

34. Return over the now-safe bridge, battling Xenomorphs along the way. Turn right and exit the area through the green doors.

35. Chell remarks, "What a beautiful mural. I wonder if the Idryll created it."

36. To your left is another set of symbols. Phaser fire pushes them back, and the wall itself recedes, revealing Golden Starship 32. Ascend the stairs and exit through the green door behind the mural.

37. Chell needs you to defend him while he disables the security system. Begin by knocking out the ceiling turrets.

38. Several waves of turret attacks follow. Keep them off Chell so he can reach the console and disable the security system.

39. Pass through the green door on the second level to find the, er, um...archeologists.

40. This is a secret area with 10 shielding.

41. Take this lift to the lower level, where more Xenomorphs and ceiling turrets await.

42. Battle your way to the indicated area and activate your night vision. Golden Starship number 33 is hidden in a secret tunnel.

43. Destroy this door to find a secret area with Idryllium.

44. Fight your way past the Xenomorphs and go through this door. Note the health and energy terminals on the right.

45. Boss time. Approach the other side and the Basher busts through the door on the right. He goes down pretty quickly against the Arc Gun and there's an energy terminal available here as well.

46. "Use" this Bridge Control Panel and a bridge drops into place.

47. Pass to the other side and this guy busts out. Again, the Arc gun works well.

48. Jump over the railing to find Golden Starship 34.

49. Return via this ladder.

50. Pass through this green door to find the Idryll son and end the mission.