Editing Deus Ex (video game) (section)

===Game design===
The original design documented cited the gameplay inspirations as ''[[Half-Life (video game)|Half-Life]]'', ''[[Fallout (video game)|Fallout]]'', ''Thief: The Dark Project'', and ''[[GoldenEye 007 (1997 video game)|GoldenEye 007]]''; the game as a whole was meant to be "genre-busting".<ref name="GamaSpectre"/> Spector later cited the limited choices available in ''[[Suikoden (video game)|Suikoden]]'' as an inspiration for the broad range of story and gameplay options in ''Deus Ex''.<ref name="SilSpector"/> Spector's aim with the gameplay was to allow as much player freedom as possible; his design document and personal goals included "problems, not puzzles", "no forced failure", "players do; NPCs watch", and "areas with multiple entrance and exit points".<ref name="GamaSpectre"/> These early designs underwent extensive expansions and alterations during early production.<ref name="USGdeleted"/> An early commitment was making level areas open-ended, with multiple ways to resolve gameplay and story situations. The opening "[[Liberty Island (Deus Ex)|Liberty Island]]" was designed as a [[vertical slice]], showing off the various gameplay elements the team wanted to implement overall.<ref name="RPSretro"/> There were some limitations put in place such as restricting what and how many augmentations the player could have access to, which Spector explained as promoting variety between players.<ref name="IGNinterview"/>

The team opted to license a third-party engine for the game rather than building their own, which ultimately gave more time for story and gameplay development. They ultimately settled on the [[Unreal Engine 1|Unreal Engine]] as it would cover most of what they wanted to do from a design perspective, and was easy for their programmers to handle.<ref name="GamaSpectre"/> As the Unreal Engine was designed for first-person shooters, the RPG mechanics such as leveling and inventory were added by the developers, alongside additional graphical elements like lip syncing for dialogue.<ref name="CGWinterview"/> Programmer Scott Martin implemented a wide range of new NPC behavior including patrols, idling, and sitting down. During early testing the enemy reactions were so acute that Martin had to adjust their behavior and detection protocols to be more forgiving.<ref name="TechRetro"/> The AI coding caused problems until late into development, with the team building on Unreal Engine's existing code and causing unpredictable NCP behavior as a result.<ref name="GamaSpectre"/> Designer [[Doug Church]] provided help with some of the AI programming.<ref name="RPSretro"/>

Spector described the early high-concept work on the game as the smoothest period, with later production running into repeated issues. The game's scale and conflicting suggestions from playtesters began causing problems for the team. The production milestones necessitated trimming or altering features; Spector recalled Smith using the phrase "Less is more" in reference to these elements.<ref name="GamaSpectre"/> There were also conflicts between the two design teams headed by Smith and Norden, described by Spector as "a bunch of knock-down drag-out fights".<ref name="DEIWgama"/> The team's morale also suffered due to negative press surrounding Ion Storm during and after the release of ''[[Daikatana]]'' (2000).<ref name="GamaSpectre"/> Planned environments also needed to be scaled down.<ref name="EdgeMakingOf"/> Some content was cut entirely including a female option for JC Denton,<ref name="IGNpreview"/> and stages set in the [[White House]], [[Russia]], and on board a space station.<ref name="USGdeleted"/><ref name="IGNinterview"/> Finished elements from those levels were incorporated into the final story and levels.<ref name="USGdeleted"/> The feature Spector most regretting dropping was plans for multiplayer that would have featured at release, describing the other dropped content as "just kind of stupid stuff".<ref name="IGNinterview"/> By contrast, Martin was upset that those sections had to be cut, but understood they had to release the game due to troubles with Ion Storm's other titles.<ref name="TechRetro"/>