The original Pokémon Red and Green games were developed for Nintendo's Game Boy.
The monochrome handheld was important to Pokémon's design because its Game Link Cable allowed two players to connect separate systems. That connection made trading central to the games rather than merely an optional feature. Some Pokémon were exclusive to one version, so completing the Pokédex required trading with another player.
Pocket Monsters Red and Green launched in Japan on February 27, 1996. Later, an enhanced Blue version was released in Japan, and that version was reprogrammed for the international Pokémon Red and Blue releases. The original Japanese Green was not released overseas.
Pokémon Yellow later added limited Game Boy Color support and drew more directly from the anime. The main series subsequently moved through Nintendo handhelds including the Game Boy Color, Game Boy Advance, Nintendo DS, and Nintendo 3DS before reaching the Nintendo Switch.