SuperTux

SuperTux is classical sidescrolling platformer in 2D, starring Tux, the Linux mascot, as main character. Tux has to rescue the penguin Penny from the clutches of the evil Nolok.

The gameplay of SuperTux is heavily influenced by Super Mario Bros. Tux in his normal form dies at one hit, but he can transform to Super Tux if he finds an egg, and he can throw fireballs if he finds a fireflower (which only appears when he's Super Tux). Tux can collect coins, which in the current version are used to activate save point within a level (otherwise, Tux has to go through a level all over again if he dies).