Allow actor to do something in this world, in the context of this circle; return the new state of the actor if something was done, nil if nothing was done. Circle is expected to be one of

• :active - actors within visual/audible range of the player character;
• :pending - actors not in the active circle, but sufficiently close to it that they may enter the active circle within a short period;
• :background - actors who are active in the background in order to handle trade, news, et cetera;
• other - actors who are not members of any other circle, although I’m not clear whether it would ever be appropriate to invoke an act method on them.

The act method must not have side effects; it must only return a new state. If the actor’s intention is to seek to change the state of something else in the game world, it must add a representation of that intention to the sequence which will be returned by its pending-intentions method.

Returns a sequence of effects an actor intends, as a consequence of acting. The encoding of these is not yet defined.