I Wanna Be the Guy (IWBTG) is a freeware platform game created by Michael "Kayin" O'Reilly for Microsoft Windows using Multimedia Fusion 2. First released on October 5, 2007, the game is no longer in active development, though the game's source code was released by Kayin in 2011 and a remastered edition was released in 2020. IWBTG has unusually difficult platforming elements, unorthodox level design, and uses sound effects, characters, and music from many other games.