Most games have what's called an "update cycle". One way or another, there are a bunch of entities/objects with an update () function, which is called periodically (usually every frame.) These might control enemy logic, particle positions, animations, etc.

Here is something that I have found to be incredibly helpful in reducing bugs.

Actually, I mean to talk about a far more important topic: the separation of Game and World.

A piece of software is, first, an organic whole. However, we've all had to unravel somebody else's spaghetti (or, better, our own) and know that it's useful to break that whole into organized pieces. You might use object oriented programming, for instance.