(2Dimensional) Objects that are rendered visually on paper, film or on screen in two planes representing width and height (X and Y). Two-dimensional structures are also used in the construction of 3D objects. See 3D and CAD.
Perhaps the most interesting feature of this game is that players can dynamically switch between a 2D and 3D gaming environment, navigating their way through classic Mario-themed stages.
Perhaps one of the most imaginative games available on the Wii, World of Goo was developed by Kyle Gabler and Ron Carmel, both of whom formerly worked for Electronic Arts and subsequently created their own independent studio called 2D Boy.
Still the game is not without its positive merits, as the first 3D (albeit isometric) Sonic game the visuals looked stunning at the time and were a breath of fresh air compared to the traditional side on 2D graphics of previous years.
Take a look at the next game you play, especially a 3D game like a racer or First Person Shooter, because you will notice that there are 3D objects and 2D objects (most likely in the background).
It was a top-down 2D game featuring the same action that's now so well-known: driving, shooting enemies and innocents both, fighting the cops, carjacking, thieving and robbing.