The mod consists of Duke Nukem 3D v0.99 Beta but with added episodes from v1.3d of Duke Nukem 3D. These added maps have been modified for v0.99 compatibility. Notably, the mod also includes the Space Suit and Flamethrower, which were scrapped from the commercial release and only partially coded in the original beta version 0.99.
The mod was originally created in 2009 by a Duke Nukem forums user named Marcos and was subsequently expanded in 2012 by users LakiSoft (also known as "Duke Nukem IV Guy" or "Gingis Khan") and Linush.
Several updated versions of the mod have been released since 2012. Bug fixes include an improved USER.CON file, new sound files, and compatible map files. The compatible map files replaced all of the map files from the original version of the mod. This is because the scope of Marcos's original project was limited only to E2L8.MAP, so Dark Side was the only 0.99-compatible map prior to the updates.