The Game Boy is a handheld console made by Nintendo in 1989. It was one of the most successful handhelds made due to the popularity of Tetris and later the Pokémon franchise. There are three models of the Game Boy; the original (known widely as the "grey brick"), the smaller Pocket with an improved screen, and the Light which was similar to the Pocket in shape and included a screen with a light, but was only released in Japan. Released several years into the life of the system was the Super Game Boy, a cartridge with a slot to play Game Boy games on the SNES in limited color with a possibility of having full color segments, and may also have improved sound. Donkey Kong GB is one of the games that took advantage of those features.
In 1998, Nintendo developed the the Game Boy Color that offers limited color (but not in the same fashion as the Super Game Boy), with eight color palettes each for sprites and tiles (doubled from the NES' four) at any given time. With it came a range of Game Boy Color-only games on clear cartridges and dual Game Boy and GBC games on black cartridges with the same shape as the original grey cartridges used for the original Game Boy. The Game Boy Color has a faster processor and has an infra-red sensor as a way of transferring data or for features such as the remote control function on Mission Impossible.
Considering that the Game Boy is often an emulator programmers first port of call due to its simplicity and is well documented, there are plenty of options. Most Game Boy Advance emulators also emulate the Game Boy and the Game Boy Color as well. Some SNES emulators such as bsnes and Higan can emulate the Super Game Boy. Many of these also include a tile viewer and even a background viewer.
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SameBoy is considered the most accurate Game Boy emulator and is the only accurate emulator that works on the Spidersoft Pinball games.
VisualBoyAdvance (abbreviated as VBA) is a common and easy to use emulator with most of the traditional features of modern emulators. It can emulate Game Boy, Super Game Boy, and Game Boy Color, titles (with SGB games losing out on the SNES SPC700 sounds) and includes screenshot support, save states, and map and tile viewers.
While bsnes is a SNES emulator, it along with Higan also emulates the Super Game Boy. Higan also emulates the Game Boy and the Game Boy Color however is not the most accurate in terms of GB emulators. It is also one of the few emulators that not only emulates the Super Game Boy but all the features including the improved sound from the SNES SPC700 sound chip that most emulators skip on.