DarcNES is a multi-system emulator. Some of the systems it emulates
are
  o Sega Master System, Sega Game Gear (with sound)
  o Nintende Entertainment System (with sound)
  o PC-Engine
and in development is support for
  o Colecovision
  o Sega Megadrive, also known as Sega Genesis
  o Apple ][

The keys are: 'A', 'S', '[', ']', arrows, and escape.

By Nyef (Alastair Bridgewater).