Abstract: In one embodiment, a system includes a data bus to receive first tracking data from a first tracking device and second tracking data from a second tracking device, a hardware processor to calculate a first position of a first symbol on a display using the first tracking data, calculate a second position of a second symbol on the display using the second tracking data, compare a proximity of the first and second position on the display, and in response to the first position and the second position having a predetermined proximity to each other on the display, perform a selection command, and a graphics processing unit to generate an image of the first symbol and an image of the second symbol for output to a display device for display, at the first position and the second position, respectively. Related apparatus and methods are also described.