Taking the role of a mysterious test subject, code named "Spewer", the player must vomit their way through over 60 levels while learning new abilities, changing forms and piecing together their purpose in the game.

[4] Spewer was developed by Edmund McMillen and Eli Piilonen and released on Newgrounds on May 4, 2009.

[citation needed] A group of four people developed Spewer: Edmund McMillen created the art assets for the game, and Eli Piilonen was the programmer.

In addition, Jordan Fehr worked on the sound effects and Daniel Baranowsky provided the music.

[5] Independent video game developer Derek Yu stated the game is the most mature title which McMillen has developed in terms of design.