user that the game is only compatible with Game Boy Color systems. One exception would be the Kirby Tilt 'n' Tumble game: despite the game cartridge featuring a notch, enabling it to be inserted on the original Game Boy, the game displays an error message indicating that it only plays on Game Boy Color. Chee Chai Alien and Pocket Music are incompatible with Game Boy Advance models, displaying an error message indicating that they only play on Game Boy Color. Game Boy Advance cartridges used a similar physical lock-out feature. Notches were located at the base of the cartridge's two back corners. One of these notches was placed as to avoid pressing a switch inside the cartridge slot to help stabilize it. When an older Game Boy or Game Boy Color game was inserted into the cartridge slot, the switch would be pressed down and the Game Boy Advance would start in Game Boy Color mode, while a Game Boy Advance cartridge would not touch the switch and the system would start in Game Boy Advance mode. The Nintendo DS replaced the switch with a solid piece of plastic that would allow Game Boy Advance cartridges to be inserted into Slot 2, but would prevent an older Game Boy or Game Boy Color cartridge from being inserted fully into the slot. Excluding game-specific variations, there are four types of cartridges compatible with Game Boy systems: Grey cartridges Grey cartridges (also known as class A) are compatible with all Game Boy systems, excluding Game Boy Micro. All original Game Boy games are of this type. Some of these cartridges are in alternative colors, such as red or blue for Pokémon Red and Blue, and yellow for the Donkey Kong Land series. The games on these cartridges are programmed in black and white; the Game Boy Color and later systems provide selectable color palettes for them. Some grey cartridges that were released between 1994 and 1998 have Super Game Boy enhancements. Even fewer grey cartridges were released with built-in features that made them protrude from the slot, but included the notch to be compatible with the original Game Boy (notably the Game Boy Camera). Black cartridges Black cartridges (also known as class B or Dual Mode) are compatible with all Game Boy systems, excluding Game Boy Micro. Although the games on these cartridges are programmed in color, they can still be played