As defined in Chapter 1, UI stands for user interface and encompasses all mechanisms by which the user and the game convey information to each other. When discussing the three UI systems, we talked about three ways in which the game communicates with the user – specifically through the use of GUI on an output device (i.e., a screen). However, if the user wants to communicate with the game, the user will have to have some means through which they can provide input. The game will then need to process that input.

There are two core ways in which Unity can handle input. The Input Manager or the Input System. Just as there are varying factors that would determine which UI system you may use, there are also varying factors that can help you determine which input system to use. Both systems allow you to easily process multiple types of input as if they are the same thing. For example, each system will let you process a keyboard space bar and an Xbox controller...