Not only that, but there are plenty of interrupts that may not follow a specific player order. For example, there are many cards that let you take resources when someone else takes an action, sometimes taking them not just from the supply but from the person performing the action.

If you are playing a 5-player game, with players A-E sitting in a circle, and player D has an interrupt with player A's action, how do they specify that in a PBEM game? Do you email the current game state to everyone with EVERY action that is taken? Or do players only receive the updated game state when it is their turn?

With the former, that's a lot of unnecessary email, with 4 emails being sent before a player gets to take an action.

But with the latter (one email sent only after the previous four players have taken their action), a player may miss their chance to perform an interrupt, or they may have to say "No, wait, I wanted to perform this interrupt. Let's undo the last few moves so I can perform this interrupt." If that's allowed, they would be able to see how the actions after the interrupt opportunity played out, and if they like them, they can leave them be, but if they don't like them, they can say, "Reverse time, I'm performing an interrupt of an action from three players ago" which may change subsequent actions.

(As an example, player A takes 3 wood from the "3 wood" space. Player B sees that no one else has enough wood to build a room, decides to take 4 clay, knowing that they can choose "Build Room" next time around if they see that someone after them accumulates enough wood to potentially take that space with a later action. Then Player C plays an action. BUT THEN, Player D (who just got the updated game state via email because it is their turn) says "Wait, I'm using my occupation that lets me buy one wood from a player (in this case, player A) for one food any time wood is taken from the board using an action (which player A did)." That gives Player D enough wood to choose "Build Room" as well, and they go ahead and choose "Build Room." Player B then says, "Well, if I had known Player D had enough wood to take "Build Room" after Player A's action, I would have chosen that action. I chose to take clay because I knew no one could choose "Build Room" with their next action." Then you have to undo Player B's clay action and let them trade it for Build Room, then redo Player C's action, and so on. All very messy.)

A non-PBEM alternative to this would be a central website accessible to players that always reflects the current game state like the excellent TI3Wiki.org. But that has to be maintained and updated by someone, essentially a moderator. This person would either not be able to play (due to access to information normally hidden from other players) or the website would have to be automated enough to allow moderation without access to other players' hands (which might not even be possible, and if it is, I'm honestly not going to put in the work to figure it out).

In short, I can't quite figure out how a PBEM game would logistically handle interrupt opportunities. I think the best option (not requiring a non-playing moderator--who wants to be that?) would be to mail out the game state after every action, thus giving people an opportunity to play interrupts. But then, how do you know if an interrupt is going to be played or not? How long do you wait? If player B performs an action, how much time do you allow players D&E to perform interrupts before letting C take the next action? I think you just have to play, and if someone says "Oh wait, I'm buying one of those wood you just took from the board" (I don't remember which card that is), everyone just has to understand that such an interrupt is going to be accepted, even if someone else has taken a subsequent action. Between friends, it probably wouldn't be a problem.

Anyone have a better solution?