The game features an internal server browser for finding other players online, and the external Galaxy program performs the same function without having to launch the game, akin to The All-Seeing Eye. It also serves as an IRC client for chat between players. The game uses modified Quake II physics. Most Quake II trickjumps, such as strafejumping, will work in Alien Arena. However, dodging, which isn't found in Quake II, has also been added to the game.
The game's main focus is to have the players try to survive the night, as the game features a day and night cycle, making the zombies slow and weak during the day, yet fast and aggressive during night-time. The game features a system in which the character constantly needs food and water. Objects in the world degrade through use, so the player has to search for or make new tools as the game progresses.