User blog comment:MetalMickey272/Game Idea!: SONIC ARENA/@comment-1945883-20110718015650/@comment-17720060-20110719004354

Well, when you click what stage you want to play in, a little screen is supposed to come up asking if you want to play the stage in 3D or 2D. 3D is good for single player, and 2D is good for multiplayer.