IWBTG is made up of several stages split up into many screens, which are usually pastiches of well known NES games like Tetris, Ghosts 'n Goblins, Zelda and Metroid. At the end of each stage is an oversized boss who must be defeated in order to progress. These bosses are generally rather humorous hybrids of traditional boss characters such as Mike Tyson, Dracula, and Mother Brain. The player must defeat each of the six bosses to advance to the final level of the game, and completion of the game unlocks a boss rush mode.
The player controls "The Kid", whose sprite is tiny compared to the objects in the game. The controls are simple, and are limited to left/right movement, jumping (and jumping a second time midair), and shooting. Non-boss enemies are very rare, and thus shooting is rarely used outside of boss fights. The focus of the game's controls is precision in moving and jumping.
