Plot: Lincity is a free and open-source software construction and management simulation game, which puts the player in control of managing a city's socio-economy, similar in concept to SimCity. The player can develop a city by buying appropriate buildings, services and infrastructure. Wikipedia
Plot: AssaultCube, formerly ActionCube, is an open source first-person shooter video game, based on the Cube engine. It takes place in realistic environments, with fast, arcade gameplay. Although the main focus of AssaultCube is multiplayer online gaming, a single-player mode consists of computer-controlled...
Plot: Installation 01 is an upcoming fan-made first-person shooter video game based on the Halo series and developed by Soon Studios. Installation 01 is being developed for Microsoft Windows, macOS, and Linux operating systems in the Unity game engine. Wikipedia
Plot: SuperTux is a free and open-source two-dimensional platform video game published under the GNU General Public License. The game was inspired by Nintendo's Super Mario Bros. series; instead of Mario, the hero in the game is Tux, the official mascot of the Linux kernel. Wikipedia
Plot: Mari0 is a 2012 side-scrolling platform video game developed by German indie developer Maurice Guégan and released onto his website Stabyourself.net. It combines gameplay elements from Nintendo's Super Mario series and Valve's Portal series. Wikipedia
Plot: Freeciv is a single- and multiplayer, turn-based strategy game for workstations and personal computers inspired by the proprietary Sid Meier's Civilization series. It is available for most desktop computer operating systems and available in an online browser based version. Wikipedia
Plot: Cube 2: Sauerbraten is a cross-platform, Quake-like first-person shooter that runs on Microsoft Windows, Linux, FreeBSD, OpenBSD, and Mac OS X using OpenGL and SDL. The game features single-player and multiplayer gameplay and contains an in-game level editor. Wikipedia