- 1 First Floor
- 2 Second Floor
- 3 Third Floor
- 4 Fourth Floor
First Room Enemy Skip (Legendary Only)
Immediately at the start of the level, there is a technique to skip enemy spawns, making it trivial to run through the first area. To start, run up to 343GS floating in front of you so he triggers and moves forward, then use one of the several techniques for grenade jumping above the wall on your right, putting you in the inner ring of the first floor. Once over the wall, run to the closest door on your left and go through it to backtrack back to 343GS. Once you trigger him to move forward, turn around and proceed through the level as normal. There will be no enemies until after the first door. Varations of this strategy can be seen in both IL runs and Full Game runs.
First Locked Door Enemy Skip (Legendary Only)
It is possible to halt the spawning of enemies at the first locked door on the second floor, saving you from 45 seconds of fighting in front of the door while it opens. Simply walk towards the door until the objective text "Wait here for the Monitor to open the door" shows up on your HUD, then walk back to the wall with the blue glowing panels on it. While standing there, no enemies will spawn other than a small amount of carrier forms. Wait in this position for ~35 seconds and then proceed towards the door; it should open as you arrive.
Inner Ring Faster Route/Enemy Skip
Immediately after the first locked door on this floor, do not turn right as you normally would. Continue straight towards the center of the level. Get to the edge of the dropoff and hop along the inner ring to your right. This path is not only faster than walking the normal way around the outer ring, but it also despawns many of the enemies in that area, making it optimal for all difficulties.
Second Locked Door Grenade Jump
The second locked door on this floor opens halfway and then stops for a time. Once it starts to open, a basic grenade jump will let you hop through the opening, allowing you to proceed without waiting for it to open fully.
What's on the third floor i forget
This level is a weird brown blur in my brain
Tunnel Skip Grenade Jump
Near the beginning of the fourth floor you will encounter a half-open door and a lower tunnel which is the normal path. But it is possible to grenade jump through this half-open door into the next room, saving the extra walking.
Final Door Grenade Jump
This is the toughest grenade jump in the level but is incredibly worthwhile as it skips the huge final battle of the level. The final door opens halfway, pauses for about 1 second, then resumes opening. A few seconds after this, a wave of 10+ flood spawn on the other side of the door. By timing a grenade jump to get through the door during the 1 second pause, you can hop through the opening before the flood wave spawns. Running straight to the end of the level should allow you to escape without dying on any difficulty.