The Controller - Pong to PC. Wii takes step back, Dual Shock holds steady.

[Sky Render]

Linear means that the input can only occur in a fixed few directions (ie. left-to-right, left-right-up-down, etc.). Non-linear means that the input is allowed in a much wider space, consisting of at least two free dimensions of movement (X/Y, Y/Z, or X/Z).