Trackball

A trackball is a pointing device consisting of a ball housed in a socket containing sensors to detect rotation of the ball about two axes - like an upside-down mouse, but with the ball sticking out more. The user rolls the ball with his thumb or the palm of his hand to move a cursor. Tracker balls are common on CAD workstations for ease of use and on modern portable computers, where there may be no desk space on which to use a mouse. Some clip onto the side of the keyboard and have integral buttons which have the same function as mouse buttons.

Trackballs have had some limited use in video games, particularly early arcade games. One of the more famous games to use one is Centipede. "Football", by Atari, was the first game to use a trackball, released in 1978 for the arcade. Console trackballs, meanwhile, are fairly uncommon. The Bandai Atmark, a Japanese console, had a trackball as standard for its gamepad, and the Atari 2600 had one as a peripheral, with a joystick as standard.

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