Complex sentence: Sega reprogrammed the game and ported it to its SG-1000 gaming console in Japan in 1985; while the gameplay was identical, Sega changed the backpack from a helicopter to a jetpack.
Split into simpler sentences: Sega reprogrammed the game for its SG-1000 gaming console in Japan in 1985. While the gameplay was identical, Sega changed the backpack from a helicopter to a jetpack.