Duke Nukem 3D

Duke Nukem 3D is a first-person shooter developed by 3D Realms and released by  Apogee in 1996. The story features the protagonist Duke Nukem fighting against an alien race. It contained many of the same features as Doom, although the atmosphere of the game is different: Duke Nukem 3D incorporates a fair amount of humour and sexuality mixed in with moody, largely urban or industrial themes.

Technical
While Doom and Duke Nukem 3D feature similar technology, Duke Nukem 3D feels largely technically superior when playing. The player can jump, crouch, and aim up or down. The rendering engine features slopes, overlapping and moving sectors, arbitrary scaling of textures and strong scripting capabilities. All of the game behavior is stored in external text files which can be modified to change almost any feature of the game. The registered version of the game came with an editor, "Build", which included a 3D editor mode. It is often considered the most simple editor ever made.

Trivia

 * A reference to Doom is included in Duke Nukem 3D. E1L3 contains a church. Standing in front of the cross at the front of the church, there is a switch.  Pressing this gives a red tint to the room while the horizontal bar of the cross lowers until it appears to be fully inverted.  Smashing the left stained glass window reveals a secret passageway, that may contain an Octobrain.  Walking down the passageway, a dead Doom marine can be seen. Duke says, ”That’s one doomed space marine”.
 * This scene was parodied in the computer game Blood—in the carnival level, a hidden room behind the tight-rope showroom contains a mutilated Duke Nukem hanging from a chain. Caleb immediately says "I've got time to play with YOU!". Actioning Duke swings the chain as Caleb utters, "uhh, shake it baby!"


 * Another reference could be found in the Sunsoft's unofficial Duke3D add-on "Nuclear Winter". In one area of the level "Land of Forgotten Toys" Duke is teleported to a parody of Doom's E1M1, complete with a sign reading "This Building Condemned". The player cannot access any other rooms with the exception of jumping out the windows next to the armor pedestal, where an important yellow card, a teleporter back to the rest of the level, and some dead Doom marines can be found.


 * A special utility to convert Doom-based WAD files into a format playable by the Build engine, WAD2MAP, was included on the Duke Nukem 3D: Atomic Edition CD. The program itself is currently available on various websites.


 * The Doom II megawad, Memento Mori II, released six months after Duke Nukem 3D, contains some references to this game. The first appears in the mission briefing for MAP04: Ratamahatta, in the form of an ill-fated scout named "Duck Nukem."  The second, and more famous one, is in the level itself, where the player eventually arrives at Duck Nukem's grave.  The last is in the mission briefing for MAP18: Regulate, featuring an equally ill-fated scout named "Ken BUILDerman," whose name is a reference to Ken Silverman, programmer of the Build engine.


 * More recent Doom WADs reference Duke Nukem. A Doom conversion of Duke Nukem 3D's E1M1 theater has been made using new textures and music. The Blood TC(an attempt to port the Monolith game Blood to the Doom engine) contains the dead Duke Nukem in the port of the carnival level. The extensive ZDoom-based mod Knee-Deep in ZDoom contains a dead Duke Nukem shoved into a barrel of toxic waste in E1M3. The text "Hmm, that's one nuked Duke!" appears on the screen when the player approaches.