What does the machine control in a game? Well, besides nearly everything? Just like the operator (or player) the functions of the machine (or gaming engine/programming) can be split into two categories: diegetic and non-diegetic.
Using Rimworld as an example again, a diegetic action for the machine is the interface or perceivable actions that are not under the operator’s control. In Rimworld, that means the rate at which people try to raid your colony and how they act. It also includes the friendly factions that come into your colony to trade and the messages for help or items from other factions.
A non-diegetic action for the machine is the workings behind the screen. Rimworld gives a lot of the information you need to understand the risks at which you do something. One example can be the rate of possibility at which an animal will decide to take revenge on the person hunting it. Another is fulfilling the requirements for ‘winning’, which the game considers building a spaceship and flying off the subpar world.
Video Games Deconstructed 