The WonderSwan was released in March 1999 in Japan, where he met with a certain success. It is a monochrome console that sells well despite the release one year earlier of the Game Boy Color thanks to an asset: its small size. So it has a lot of autonomy, but it is very efficient. The inventor of this console is Gunpei Yokoi, the spawner of the Game Boy. The WonderSwan knows two evolutions: the WonderSwan color which brings a color screen and the SwanCrystal which is a declination of the WonderSwan color with a better screen. These three models sold more than 2 million copies in Japan, their only market.