No. It means by default no one else is obligated to take care of you.

It's on the stable’s wall. There is none on the manger the donkey is feeding from.

Yes, and tomorrow we're going to the zoo.

There are two main parts to consider: the simulation engine, and the renderer. The level of sophistication you want to achieve for one is independent of the same for the other.

Start simply for both, and add code to either until you reach what you want.