Yoshi's Universal Gravitation (?????????, Yossh? no Ban'y? Inryoku?) also known as Yoshi Topsy-Turvy in North America, is a platformer for the Game Boy Advance that was developed by Artoon and published by Nintendo, starring Yoshi. It features a built-in tilt sensor, which is used to manipulate the game's environment. By tilting the Game Boy Advance left or right, the player can tilt the game area, causing enemies and other objects to slide as the direction of gravity changes. This gameplay mechanic is used to solve puzzles or aid Yoshi in completing levels. Due to the tilt-sensing device that is required for gameplay this game is one of the few Game Boy Advance games that is not compatible with the Game Boy Player for the Nintendo GameCube. [source:wikipedia]