Gambatte is an accuracy-focused, cross-platform Game Boy and Game Boy Color emulator. It is based on hundreds of corner case hardware tests, as well as previous documentation and reverse engineering efforts. The core emulation code is contained in a separate library back-end (libgambatte) written in pure platform-independent C++. There is a GUI that uses Trolltech's Qt4 toolkit (gambatte_qt), and a simple command-line SDL front-end (gambatte_sdl). The GUI front-end contains platform-specific extensions for video, sound, and timers.
