As I've worked on developing doom the tei tenga incident, I've found that some of the doom bible had need some changes to create variations on theme and style like the original doom. For example, we will take episode 4, City instinct which was called armed assault in the original doom bible. Compare the story snippet for the start of episode 4 from the doom bible
"Your team is in jail for destroying the planet: the officials denied tampering with
the forces. You've been promised release as soon as it blows over. Then they
recruit you to explore another gate that the military has opened on the small moon
of ????. The squads they've sent in have lost to the forces there. Demons from the
gate have stolen a new weapon and you've got to get it back. Once there, you
travel hell and find the weapon ... and it’s attached to a huge
techno-demon.You defeat him and cut the weapon off, and find its energy systems non-functional. You
go outside and head for the gate. When you return to the moon, the entire base is
covered with grotesque demonic goo"
Now compare that to the description of doom the tei tenga incidents episode 4 story setup and design brief.
"Your team is in jail for destroying the planet: the UAC has denied tampering with
portals. The team is promised to be released once the whole incident has blown over . Then they
recruit you to explore another gate that the Union Aerospace corporation has opened at its research and development facility in Luna city, on the moon. They have lost all contact with the UAAF base in the city, which was reporting massive casualties and huge amounts of demons coming out of nowhere. They fear that the city's mass driver will be used to bombard earths cities and military installation like during the revolution of 2134. You fight your way through the massive underground city, to the UAC R&D facility in its lowest level. After that the portal spits out at you a massive techno-demon with a powerful weapon attached to its arm. You destroy the demon and remove its implanted arm cannons main part, which happens to be the prototype BFG2704 multi-projectile plasma cannon, after that you head through the gateway and after a short jaunt through hell, you re-emerge to find that there is demonic goo everywhere, and the city is being turned into a huge demonic enclave with a very,very,very powerful gun in the middle of it."
This is basically the same thing, changed to fit a more complete and interesting design for a game, which allows level designers to be creative with their environments and levels instead of making a standard human tech-base on definitely not tei-tenga.
Basically the whole idea is to be able to show the differences between this episode 1 area
and this episode 4 area
This is because it allows differences in maps instead of similar looking levels in all episodes, which keeps up the variety architecture wise, and the different types of enemies and ambushes to be used, for example things like snipers and large demons, which would not fit well in the smaller base on tei tenga without having to crouch under doors, and low ceilings.
~demo_the_doomer
