Defcon 5 is a single player adventure/first-person shooter video game developed by Millennium Interactive Ltd, a UK-based studio. It was released for IBM PC compatibles, Sony PlayStation, Sega Saturn and 3DO Interactive Multiplayer in 1995. Defcon 5 actually means the condition used to designate normal peacetime military readiness while Defcon 1 refers to maximum readiness.
As a "cyberneer" working for a for the fictional Tyron Corporation the player is tasked with installing an automated defense software at the deep space mining installation named MRP-6F, a large compound located around the top of a crater in which mining operations take place. Its purpose is to defend the mining installation from hostile attack. For this purpose the installation houses six powerful defense turrets installed around the crater, as well as a myriad of support systems for power generation and munitions stores for those armaments.
Shortly after his/her arrival at MRP-6F the installation is attacked by an unknown enemy force. The player must face enemy fighters as well as invaders searching the base. The overall goal is to escape the installation with evidence of what has transpired.
The game is reminiscent of the System Shock series in terms of gameplay. The player must explore the base in order to find items which is needed to establish a line of defense and ultimately escape the installation. This involves fighting off the invading enemies by deploying the defense turrets effectively and using the installation's computer terminals (called "VOS terminals") in order to hinder the intruder's advance.The computer terminals in the game offers an unusual wide range of interaction. Players can use them to remotely control the defense turrets, load ammunition and inspect the turrets for damage and deploy combat droids within the installations perimeters. Doors can be controlled from the VOS terminals in order to control access to the installations different areas. The player can use this capability to lock in enemy forces in parts of the installation. The game also allows the player to fight the invaders by shooting them, but this is discouraged by the fact that new enemies arrives with each passing wave of attacking ships. Also, any fighting in the installation greatly degrades the air quality in the immediate area once an enemy is destroyed. The computer might even seal doors to polluted areas, sometimes trapping the player. The player can dissolve the pollution by opening doors to adjacent areas, and the pollution levels can be monitored in the VOS terminal's environmental module.' The installation is huge, consisting of two major towers with seven floors each (the administrative and domestic blocks), three hangers, a service level, six turrets and a control room. All these are linked by a subway-train like transportation system named "LIMO". Several elevator systems also connects the different levels. This complex layout enables the player to avoid enemies by choosing an alternate route to his/her destination.
Defcon5 has been listed as "supported" on the DOSBOX website since version 0.61 of the emulator software. The fact that it uses CD audio can however be a problem.[ ]