West Side Island, known as the Island of Illusion, is the setting for Sonic the Hedgehog 2 (16-bit), as told by the Japanese manual. Miles Prower lived there before his first meeting with Sonic, recieving the nickname "Tails" from the resident animals. The island's peaceful idyll is shattered when, before the start of the game, Doctor Robotnik comes to West Side searching for the Chaos Emeralds.
The Mega Drive Sonic the Hedgehog 2 is the only game to have unequivocally visited West Side Island; Sonic the Hedgehog 2 (8-bit) (along with many other early Sonic games) instead took place on South Island. Areas visited by Sonic and Tails on West Side Island include:
And above the island:
And even higher above:
Several locations in Sonic Drift 2 are the same as those in Sonic 2 (namely Emerald Hill, Casino Night, Hill Top, and Mystic Cave), so obviously occur on West Side Island too. Many of the other racetracks are Zones with no pre-existing appearences, so it is possible that several of these (like Desert Road or Dark Valley) are also located on West Side.
In Sonic Mania, there are two zones present that were already present in Sonic 2, Chemical Plant Zone and Oil Ocean Zone, but this game presents two more zones that are evidenced to be in West Side Island by the transitions, they are:
|Sonic the Hedgehog 2 (16-bit)|