==Custom maps==
The custom maps are a special case and fall into a category of their own, because they need server-side as well as client-side customization. Custom maps are automatically downloaded when a server is running it and a player tries to join that server.

Custom maps are created by community members of Natural-Selection, some of the currently official maps included in the installation once started out as custom maps. Currently only classic and combat map types are officially supported to be considered for inclusion. For a map to become official it has to meet certain [http://www.unknownworlds.com/ns/static/Mapping_Guidelines.html mapping guidelines] and has to be approved by playtesters and developers.

There are 2 official and 5 unsupported game types for these custom maps:

===Classic / Combat===
These are exactly the same game mode as explained above: [http://en.wikipedia.org/wiki/Natural_Selection_%28computer_game%29#Combat_game_mode Classic] | [http://en.wikipedia.org/wiki/Natural_Selection_%28computer_game%29#Classic_game_mode Combat]
===Alternative game types===
Important note:

All of the following game types are not officially supported by the Natural-Selection developers.
====Marines vs Marines / Aliens vs Aliens ====
Usually a modified version of combat maps to make it possible to play as marines vs marines or aliens vs aliens. There are versions out there which are built from the ground up instead of modifying an already released map
====Siege====
The goal of these maps is to have both the marine team as the alien team, tech-up to the maximum before encaging each other. The simplest construction for these maps is to have two rooms separated by a huge central door and a siege room for the marines to place siege cannons with the purpose to destroy the 3 hives.
Both teams have an huge resource flow to be able to research technology and alien abilities. After a certain amount of time the central door will open and the battle for survival begins. The basic rule for the marines is to defend their main base and to advance towards the siege location, to siege the alien hives. The aliens have to prevent this from happening and at the same time try and destroy the marine main base.
====Fun====
These maps are most of the time based on the combat game type. But in this case the map has been constructed to have a completely different graphical style from Natural Selection’s sci-fi tech or alien textures. One example had textures based on [http://en.wikipedia.org/wiki/Nintendo Nintendo’s] famous [http://en.wikipedia.org/wiki/Super_Mario_Bros Super Mario Bros]
====Natural Selection meets other hl mods====
Basically these maps are modified maps from the Half-Life mods [http://en.wikipedia.org/wiki/Counter-Strike Counterstrike], [http://en.wikipedia.org/wiki/Day_of_defeat Day of Defeat] and [http://en.wikipedia.org/wiki/Team_Fortress_Classic Team Fortress Classic]. The goal is to be able to play the Natural-Selection classic or combat game type while playing a Counterstrike, Team Fortress Classic or Day of Defeat map.