Mednafen is a portable, utilizing OpenGL and SDL, argument
(command-line)-driven multi-system emulator with many advanced
features. The Atari Lynx, GameBoy  (Color), GameBoy Advance, NES,
PC Engine (TurboGrafx 16), SuperGrafx, Neo Geo Pocket  (Color),
PC-FX, and WonderSwan  (Color) are emulated. Mednafen has the
ability to remap hotkey functions and virtual system inputs to a
keyboard, a joystick, or both simultaneously. Save states are
supported, as is real-time game rewinding. Screen snapshots may be
taken at the press of a button, and are saved in the popular PNG
file format.

Due to the threaded model of emulation used in Mednafen, and
limitations of SDL, a joystick is preferred over a keyboard to play
games, as the joystick will have slightly less latency, although
the latency differences may not be perceptible to most people.