Plot: Giana's Return is a fan-made sequel to the videogame The Great Giana Sisters. A German-Austrian-French team, the founders of the independent studio Retroguru in 2011, developed the game from 1998 to 2014. Wikipedia
Plot: OpenClonk is a free and open-source 2D action game in which the player controls clonks, small but witty and nimble humanoid beings. It is mainly about mining, settling and fast-paced melees and features tactical gameplay elements. Wikipedia
Plot: Icy Tower is a freeware computer game by Swedish game developer Free Lunch Design. It is a platform game set in a tower, where the player's goal is to jump from one floor to the next and go as high as possible without falling and plunging off the screen. 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