Tremulous is a free and open source sci-fi team based multiplayer first person shooter (FPS) game. The gameplay is mainly FPS but has some real time strategy (RTS) aspects as each side has to build and defend their base. Tremulous has some similarities to the Halflife Mod 'Natural Selection'. There are 2 sides to choose from, humans and aliens. The main objective is simple, eliminate the opposing team.
Mac OS X 10.5 or newer
Intel powered Mac
125 MB hard disk space
Internet connection for multiplayer
Free download at tremulous.net