Defcon 5 , a Sega Saturn exclusive from 1996, puts you in the shoes of an engineer tasked with updating a defence base. However, things take a turn for the worse when the base is invaded by unknown assailants. With your wits and the defence software as your only allies, you must fend off the attackers and uncover the truth behind their attack.
The game's main action takes place in first-person view inside the complex, where you must navigate through maze-like living areas and defend against waves of fighters in manned turrets. You can also scavenge for card keys during downtime to upgrade the software and unlock new features.
A key aspect of Defcon 5 is the "Virtual Operating System", which controls all major base functions. By repairing damage, monitoring intruders, and placing robot sentries, you can increase the software's efficiency and gain access to more advanced features.
Your ultimate goal is to find the clearance to self-destruct the base, defend your escape shuttle, and escape alive. As you progress through the game, the defence becomes increasingly automated, giving you more time to search for keys and uncover the secrets behind the attack.