Syobon Action, sometimes called Cat Mario, Shobon Action or Action Shobon, is a freeware game from Japan. The first complete version was released on the game's official website.
Later, an open source version of the game was released which lead to not only the Windows version but also ports for AmigaOS 4.1 and Linux. The official version from the website is only at 10mb.
The gameplay is very similar to Super Mario Bros. However, the game is filled with hidden traps that make this game significantly more challenging - particularly to players that are familiar with the tropes found in Super Mario Bros. For example, eating a red mushroom is beneficial in Super Mario Bros.; however, in Syoban Action, if the player eats a red mushroom, they will become so strong that they fall through the ground and die.
To balance the extreme difficulty, players have an infinite amount of lives. Players start with three lives, but there is no penalty for losing all of them. Instead, once the three lives are used up, the life counter continues into negative numbers, effectively nullifying the lives mechanic.