joystick) changes the speed and direction of the movement of the on-screen pointer. translation vs. rotation Another classification is the differentiation between whether the device is physically translated or rotated. degrees of freedom Different pointing devices have different degrees of freedom (DOF). A computer mouse has two degrees of freedom, namely its movement on the x- and y-axis. However the Wiimote has 6 degrees of freedom: x-, y- and z-axis for movement as well as for rotation. possible states As mentioned later in this article, pointing devices have different possible states. Examples for these states are out of range, tracking or dragging. Examples a computer mouse is an indirect, relative, isotonic, position-control, translational input device with two degrees of freedom (x, y position) and two states (tracking, dragging). a touch screen is a direct, absolute, isometric, position-control input device with two or more degrees of freedom (x, y position and optionally pressure) and two states (out of range, dragging). a joystick is an indirect, relative, elastic, rate-control, translational input device with two degrees of freedom (x, y angle) and two states (tracked, dragging). a Wiimote is an indirect, relative, elastic, rate-control, translational input device with six degrees of freedom (x, y, z orientation and x, y, z position) and two or three states (tracking, dragging for orientation and position; out-of-range for position). Buxton's taxonomy The following table shows a classification of pointing devices by their number of dimensions (columns) and which property is sensed (rows) introduced by Bill Buxton. The sub-rows distinguish between mechanical intermediary (i.e. stylus) (M) and touch-sensitive (T). It is rooted in the human motor/sensory system. Continuous manual input devices are categorized. Sub-columns distinguish devices that use comparable motor control for their operation. The table is based on the original graphic of Bill Buxton's work on "Taxonomies of Input". Buxton's Three-State-Model This model describes different states that a pointing device can assume. The three common states as described by Buxton are out of range, tracking and dragging. Not every pointing device can switch to all states. Fitts' Law Fitts's law (often cited as Fitts' law) is a predictive model of human movement primarily used in human–computer interaction and ergonomics. This scientific law predicts that the time required to rapidly move to a target area is a function of the ratio between the distance to the target and the width of the target. Fitts's law is used to