when we talk about a game, or simulation, we tend to think of an advanced AI with design and operation of complicated mechanisms (radar, logistics, etc.), however, there is a simpler shortcut .. it would be enough to make a vehicle workable, truck, train , boat or plane to play by performing simple tasks, rescues, loads of goods .. even a simple mechanical shovel dismantling a ground is a game ..
it depends on how complicated we want to do it ..
An example.
This is a Mi-8MTV2 helicopter from DCS, your task is to wait for an emergency call and go to the rescue.
Fun and relaxing.
Outerra has that within reach, since it is the most difficult theater.