: I've always wondered what is with Marathon RED during the last several
: levels. What was with the overlapping rooms, the invisible characters,
: repeating levels and other things?
From what I remember, they're sort of akin to dream levels, representing your final journey into the same state of being that Michael and Joshua have attained (well, not really, since M and J are implied as being W'rkncacnters, and in the level "3", Michael elevates you practically to his level (seemingly unknowingly, since I don't think he appreciates the power of your Jjaro implants).
I believe the "ghosts" represent you destroying your own inner demons.
Anyway, try to search for the old RED Volunteers series posts by Mark Levin; he does a fantastic job with RED's plot and design.