What open source platform game was modeled after a Nintendo game released in 1985 that required players to rescue Princess Toadstool?
Super Mario Bros.:  Released as a sequel to the 1983 game "Mario Bros.", "Super Mario Bros." was released in Japan and North America in 1985, and in Europe and Australia two years later. Super Mario Bros.:  In "Super Mario Bros.", the player controls Mario and in a two-player game, a second player controls Mario's brother Luigi as he travels through the Mushroom Kingdom in order to rescue Princess Toadstool from the antagonist Bowser.
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