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.

The megawad 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.

On 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 secret exit definitions for E2M4 and E2M5 in the MAPINFO lump were switched, so that the player reaches E2M9 from E2M4 and E5M1 from E2M5, instead of the other way around. Unfortunately, the exit definitions for E2M9 and E5M1 (leading to E2M6 and E2M5, respectively) were not updated to match this, resulting not only in the player being unable to reach both secret levels in a single playthrough, and not only in the player being able to skip E2M5 by reaching and finishing E2M9, but in E5M1 taking the player back to the level they entered it from after finishing it.

Levels
Deep into the Code: Road to Eternity: The Evil Unleashed: The Search for Stephanie:
 * 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)
 * E5M1: The Mighty Green by Paul Corfiatis (secret level; ZDoom-only)
 * 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)