Missingno is an emulator for the Game Boy, Game Boy Color, Atari VCS
(2600), and Sega SG-1000. It is built around faithful models of the
original hardware:
games look, sound, and behave as they do on the real machines, with
display options that recreate the look of the original LCD and CRT
screens.

The library manages your collection: cover art and metadata are fetched
automatically, play sessions and screenshots are recorded, and saves are
managed and backed up. Homebrew games can be browsed and downloaded from
Homebrew Hub, and physical cartridges read and written with a GBxCart RW.

The integrated debugger works across every supported system, with
disassembly, breakpoints, and live inspection of CPU, video, and audio
state.