Wraparound, in video games, is when an object moves off of one side of the screen and reappears on the other side. In Asteroids for example, the player's ship flies off of the right side of the screen, then continues on the left side with the same velocity. This is referred to as wraparound, since the top and bottom of the screen wrap around to meet, as do the left and right sides (topologically equivalent to a Euclidean 2-torus).[1]
Some games wrap around in certain directions but not others, such as games of the Civilization series that wrap left to right, but the top and bottom remain edges, representing the North and South Pole (topologically equivalent to a cylinder). Some games such as Asteroids have no boundary and objects can travel over any part of the screen edge and reappear on the other side.[2] Others such as Pac-Man, Wizard of Wor, and some games in the Bomberman series, have a boundary surrounding most of the playing area, but have a few paths connecting the left side to the right, or the top to the bottom, that characters can travel on. Wraparound can apply to scrolling games such as Defender, where the player can infinitely fly in one direction because the horizontal extents of the landscape are connected. Some games even incorporate diagonal wraparound, where movement from one corner of the screen wraps to the opposite corner.