2002 A Doom Odyssey

2002 A Doom Odyssey is a 2002 megawad for The Ultimate Doom which replaces all four episodes. The project was organized by Paul Corfiatis, who designed most of the levels, and also composed the megawad's soundtrack.

A sort of demo version with just the first episode was released on December 20, 2000. Back then, the planned name was 2001 A Doom Odyssey. The megawad itself, properly speaking, was first released on July 24, 2002. A second version was released on August 30, 2002, with changes to E1M3, E1M5, E2M2, E4M2, E4M5 and E4M6, as well as an additional level that can only be reached when the megawad is played in a ZDoom-based source port.

In 2003, it was listed as one of the top 10 WADs of 2002 in the Top 100 WADs of All Time article series during Doomworld's celebration of Doom's 10th birthday. July 30, 2004, a third version was released, with fixes to the megawad's MAPINFO lump, allowing every episode to be completed in ZDoom, as well as various fixes to certain levels. In addition, the entrance maps (E2M5 and E2M4) of episode 2's secret levels (E2M9 and E5M1, respectively) were switched but the exit maps of the secret levels were left unmodified, resulting in gameplay problems. See the glitch with secret levels for more information.

For the tenth anniversary, a new update was released on July 27, 2012, though with a different file name (2002ad10) so as not to replace the previous. It added another new level and reshuffled some existing ones again. A minor bugfix for this tenth anniversary edition was issued on August 2, 2012.

Levels
Deep into the Code: Road to Eternity: The Evil Unleashed: The Search for Stephanie: Bonus ZDoom levels:
 * E1M1: The Entry by Paul Corfiatis
 * E1M2: Helicopter Bay by Kristian Aro
 * E1M3: The Doomed Lab by Paul Corfiatis (Exit to secret level)
 * E1M4: Substation 537A by Kristian Aro
 * E1M5: Combat Station by Paul Corfiatis
 * E1M6: Toxic Treatment Plant by Kristian Aro
 * E1M7: Service Base by Paul Corfiatis
 * E1M8: Paradox by Kristian Aro
 * E1M9: Lugano Base ZR-X by Paul Corfiatis (secret level)
 * E2M1: Station Alpha by Paul Corfiatis
 * E2M2: Station Beta by Chris Hansen
 * E2M3: The Lost Labs by Rory Habich
 * E2M4: Shotgun Blues by Paul Corfiatis (Exit to secret level; ZDoom-only)
 * E2M5: Fortress of Fatalities by Paul Corfiatis (Exit to secret level)
 * E2M6: Between Demons n' Insects by Rory Habich
 * E2M7: Puzzles to Solve by Kristian Aro and Paul Corfiatis
 * E2M8: Total Disturbance by Paul Corfiatis
 * E2M9: Dungeon of Hate by Paul Corfiatis (secret level)
 * E3M1: Gatehouse by Sam Woodman
 * E3M2: Caves of Bosnia by Paul Corfiatis
 * E3M3: Stronghold of Damnation by Rory Habich
 * E3M4: Hall of Ebola by Rory Habich
 * E3M5: De-Moon Side by Vick Bobkov
 * E3M6: Obituary Written by Chris Hansen (Exit to secret level)
 * E3M7: System Central by Paul Corfiatis
 * E3M8: Spider Temple by Paul Corfiatis
 * E3M9: The Lost Chord by Sam Woodman (secret level)
 * E4M1: Play School by Paul Corfiatis
 * E4M2: Back to Base X by Anthony Soto (Exit to secret level)
 * E4M3: Hell Unleashed by Chris Hansen
 * E4M4: Disreputable Stronghold by Chris Hansen
 * E4M5: Indomitable Haunt by Chris Hansen
 * E4M6: Dementia by Joe Pallai
 * E4M7: Odious Grounds by Chris Hansen
 * E4M8: Impossible Mission by Paul Corfiatis
 * E4M9: Secret Wolfenstein Level by Paul Corfiatis (secret level)
 * E5M1: The Mighty Green by Paul Corfiatis (E2 secret level, exit back to E2M5)

Soundtrack

 * E1M1: "Barrels n' Troopers"
 * E1M2: "What's around the corner?"
 * E1M3: "No fear!"
 * E1M4: "CityWoman choir"
 * E1M5: "Sexy!"
 * E1M6: "Rock it!, Cock it!"
 * E1M7: "Race Against Time"
 * E1M8: "Imperial Solutions"
 * E1M9: "Dance of the Trooper"
 * E2M1: "Banjo lovers delight"
 * E2M2: "Arch-Vile Cathedral band"
 * E2M3: "The Choice"
 * E2M4: "Popdoom"
 * E2M5: "Eternal sadness"
 * E2M6: "Hysterical horror"
 * E2M7: "Waltz of the Damned"
 * E2M8: "Totally evil"
 * E2M9: "Viva la Crypt"
 * E3M1: "Runaway Train"
 * E3M2: "Spirit world II"
 * E3M3: "Feel the pain!"
 * E3M4: "Skull of the Revenant"
 * E3M5: "Moonrise"
 * E3M6: "Intensity"
 * E3M7: "Backfire"
 * E3M8: "Gunshot Dance"
 * E3M9: "Party in Hell"
 * E4M1: "Arch-Vile Cathedral band" (ZDoom-only) or "Skull of the Revenant"
 * E4M2: "Popdoom" (ZDoom-only) or "Spirit world II"
 * E4M3: "Viva la Crypt" (ZDoom-only) or "Feel the pain!"
 * E4M4: "Runaway Train" (ZDoom-only) or "Sexy!"
 * E4M5: "Skull of the Revenant" (ZDoom-only) or "Waltz of the Damned"
 * E4M6: "Eternal sadness" (ZDoom-only) or "Popdoom"
 * E4M7: "Totally evil" (ZDoom-only) or "Hysterical horror"
 * E4M8: "Gunshot Dance" (ZDoom-only) or "Eternal sadness"
 * E4M9: "Get Them Before They Get You" (by Bobby Prince, from Wolfenstein 3D) (ZDoom-only) or "Dance of the Trooper"
 * E5M1: "Sam & Max, Surfin' the Highway"

Tenth anniversary edition
The 2012 update replaced the rather amateurish endgame screens and intermission pictures with screenshots of the levels. It also renamed episode 4 from "The Search for Stephanie" to "Torment Ultima". The original E4M1 was replaced by a brand-new one, E4M9 was shuffled to E5M2, E3M5 was shuffled to E4M9, and a brand new E3M5 was added. The original MIDI soundtrack was slightly tweaked, and ten new songs were added to give episode 4 its own original soundtrack. Some of the levels were subtly renamed.

E3 was also given a second secret level when the Wolfenstein level was moved out of E4. Exits here also head back to the correct levels.

Levels
Deep into the Code: The Road to Eternity: The Evil Unleashed: Torment Ultima: Bonus ZDoom levels:
 * E1M1: The Entry by Paul Corfiatis
 * E1M2: Helicopter Bay by Kristian Aro
 * E1M3: The Doomed Lab by Paul Corfiatis (Exit to secret level)
 * E1M4: Substation 537A by Kristian Aro
 * E1M5: Combat Station by Paul Corfiatis
 * E1M6: Toxic Treatment Plant by Kristian Aro
 * E1M7: Service Base by Paul Corfiatis
 * E1M8: Paradox by Kristian Aro
 * E1M9: Lugano Base ZRX by Paul Corfiatis (secret level)
 * E2M1: Station Alpha by Paul Corfiatis
 * E2M2: Station Beta by Chris Hansen
 * E2M3: The Lost Labs by Rory Habich
 * E2M4: Shotgun Blues by Paul Corfiatis (Exit to ZDoom bonus level E5M1)
 * E2M5: Fortress of Fatalities by Paul Corfiatis (Exit to secret level)
 * E2M6: Between Demons and Insects by Rory Habich
 * E2M7: Puzzles to Solve by Kristian Aro and Paul Corfiatis
 * E2M8: Total Disturbance by Paul Corfiatis
 * E2M9: Dungeon of Hate by Paul Corfiatis (secret level)
 * E3M1: Gatehouse by Sam Woodman
 * E3M2: Caves of Bosnia by Paul Corfiatis
 * E3M3: Stronghold of Damnation by Rory Habich
 * E3M4: Halls of Ebola by Rory Habich
 * E3M5: Blood and Guts by Paul Corfiatis (Exit to ZDoom bonus level E5M2)
 * E3M6: Obituary Written by Chris Hansen (Exit to secret level)
 * E3M7: System Central by Paul Corfiatis
 * E3M8: Spider Temple by Paul Corfiatis
 * E3M9: The Lost Chord by Sam Woodman (secret level)
 * E4M1: Unity by Paul Corfiatis
 * E4M2: Back to Base X by Anthony Soto (Exit to secret level)
 * E4M3: Hell Unleashed by Chris Hansen
 * E4M4: Disreputable Stronghold by Chris Hansen
 * E4M5: Indomitable Haunt by Chris Hansen
 * E4M6: Dementia by Joe Pallai
 * E4M7: Odious Grounds by Chris Hansen
 * E4M8: Impossible Mission by Paul Corfiatis
 * E4M9: De-Moon Side by Vick Bobkov (secret level)
 * E5M1: Surfing the Mighty Green by Paul Corfiatis (E2 secret level, exit back to E2M5)
 * E5M2: Secret Wolfenstein Level by Paul Corfiatis (E3 secret level, exit back to E3M6)

Soundtrack

 * E1M1: "Barrels n' Troopers"
 * E1M2: "What's around the corner?"
 * E1M3: "No fear!"
 * E1M4: "CityWoman choir"
 * E1M5: "Sexy!"
 * E1M6: "Rock it!, Cock it!"
 * E1M7: "Race Against Time"
 * E1M8: "Imperial Solutions"
 * E1M9: "Dance of the Trooper"
 * E2M1: "Banjo lovers delight"
 * E2M2: "Arch-Vile Cathedral band"
 * E2M3: "The Choice"
 * E2M4: "Popdoom"
 * E2M5: "Eternal sadness"
 * E2M6: "Hysterical horror"
 * E2M7: "Waltz of the Damned"
 * E2M8: "Totally evil"
 * E2M9: "Viva la Crypt"
 * E3M1: "Runaway Train"
 * E3M2: "Spirit world II"
 * E3M3: "Feel the pain!"
 * E3M4: "Skull of the Revenant"
 * E3M5: "Demon's March"
 * E3M6: "Intensity"
 * E3M7: "Backfire"
 * E3M8: "Gunshot Dance"
 * E3M9: "Party in Hell"
 * E4M1: "Lock and Load" (ZDoom-only) or "Skull of the Revenant"
 * E4M2: "Mechanical Sadness" (ZDoom-only) or "Spirit world II"
 * E4M3: "Medieval Maniac" (ZDoom-only) or "Feel the pain!"
 * E4M4: "Battle of Satanic Forces" (ZDoom-only) or "Sexy!"
 * E4M5: "The Chase" (ZDoom-only) or "Waltz of the Damned"
 * E4M6: "Dark Corner of Fear" (ZDoom-only) or "Popdoom"
 * E4M7: "Hot Ash" (ZDoom-only) or "Hysterical horror"
 * E4M8: "Confusing" (ZDoom-only) or "Eternal sadness"
 * E4M9: "Moonrise" (ZDoom-only) or "Dance of the Trooper"
 * E5M1: "Sam & Max, Surfin' the Highway"
 * E5M2:

Glitch with secret levels
For the third version (published on July 30, 2004), the secret exit definitions of E2M4 and E2M5 in the MAPINFO lump were swapped. Unfortunately, the exit definitions of the secret levels (E2M9 and E5M1) were not updated to match this. It had the following consequences:
 * 1) The player is unable to reach both secret levels in a single playthrough.
 * 2) The player is able to skip E2M5 by reaching and finishing E2M9.
 * 3) E5M1 takes the player back to the level they entered it from after finishing it.

The problem was fixed in the tenth anniversary edition, where E2M4's secret exit was changed to send the player to E5M1 again, while the hidden exit of E2M5 was edited to lead to E2M9. Thus, the secret levels caused no more disruption in the progression of the episode.

The table shows the arrangement differences between the megawad versions:

Note that the dates listed for both V2 and the 10th Anniversary Edition are misleading, as the files themselves are the third version and the August bugfix, respectively.