The first handheld console produced by Bandai. It was soon replaced by the WonderSwan Color to compete with the success of Nintendo Game Boy.
WonderSwan in MESS requires a cart dump in .ws, .wsc or bin format to work. To run it, you can use the “cartridge” (cart) device, e.g. from command line
mess wswan -cart "C:\pathtogame\gamename.ws"
A list of WonderSwan software can be found here.
WonderSwan emulation in MESS still has imperfect sound.
WonderSwan is a handheld game console released in Japan by Bandai in March 1999. It was designed by Koto, a company founded by Gunpei Yokoi (the man whose designed the original Nintendo Game Boy), and Bandai. The WonderSwan was made to compete with the SNK Neo Geo Pocket Color and the Nintendo Game Boy Color, the market leader.
The WonderSwan was available in ten different case colors. Part of its success was due to a fairly large library of games, including many titles based on popular Japanese manga and anime brands, thanks to Bandai's licenses.
As it was a console designed essentially for the Japanese market, most of the games are in Japanese, with only a few featuring English text.
The WonderSwan was later replaced by the WonderSwan Color, an evolution of the hardware featuring a color display. Although some WonderSwan Color games are compatible with the original WonderSwan, many are designed exclusively for the WonderSwan Color. The latter ones show a “This cartridge is for WonderSwan Color only” message when run on the original WonderSwan.
(info based on Wikipedia)