DEFCON features multiple game modes, all of which affect how the game plays. With all game modes, the winner is determined by score, which is affected by which score mode is chosen.
As expected, this is the default setting. It's typically all against all warfare with the standard time settings for each DEFCON level.
Office Mode Edit
Office Mode is, as the name suggests, catered to be played during over the course of a working day. the game is designed to go for eight hours, and is programmed to be easy to hide if a supervisor happens to walk by and has no sound.
Speed DEFCON Edit
Similar to default, but faster, for those who just want a quick game. Speed is set to maximum and cannot be changed. Games will last no longer than 15 minutes.
A greater emphasis is placed on creating alliances and either breaking them at opportune moments or keeping them strong, as all players are allied in the green alliance at the start of play.
Big World Edit
The range of weapons, RADAR and all units are halved, along with unit speed.
A tournament style game
You set the parameters, all things are adjustable.