Super Mario Bros. X is a freeware based off the 16-bit era Mario console games. The game's included world, which contains over 50 main levels, along with multiple bonus levels, has elements from Super Mario Bros., Super Mario Bros. 2, Super Mario Bros. 3, Super Mario World, Zelda, and Metroid. It is written in Visual Basic for the Windows platform.
The gameplay of Super Mario Bros. X is very similar to the games it was intended to emulate. However, there are several new elements. Simultaneous two player co-op is one of the major features of this fangame. During a two-player game the screen will split and recombine as the players separate and come together. Other new gameplay elements are the ability to fly the Koopa Clown Car that Bowser used in Super Mario World, plus the Billy Gun, which shoots Bullet Bills when picked up, and five playable characters; Mario, Luigi, Toad, Peach, and Link.
Super Mario Bros. X comes with the same level editor that was used to make the main campaign. It can create levels and world maps, which gives users the ability to create and share their own full-fledged game episodes. It is received in a bipolar way; some absolutely love it because it is easy to use and learn, while others hate it because any level programming knowledge is put to no use at all, leaving some to side with Game Maker.