Which handheld system was Pokémon Ruby and Sapphire developed for?

Pokémon Ruby and Sapphire were developed for the Game Boy Advance.

The pair were the first main-series Pokémon games designed for Nintendo’s 32-bit Game Boy Advance hardware. They used the system’s improved processing power and color capabilities to present a new region, new battle features, and more detailed environments than the earlier Game Boy Color titles.

Ruby and Sapphire were released in Japan on November 21, 2002, followed by international releases in 2003. Their platform transition also changed connectivity: the games could link with other third-generation titles but could not directly trade or battle with the earlier Game Boy generations.

The games became the best-selling titles for the Game Boy Advance. Their successors included Pokémon Emerald, while remakes titled Pokémon Omega Ruby and Alpha Sapphire later appeared on the Nintendo 3DS.