The Iocane Powder Problem is my name for a problem I’ve seen occur in a lot of games. Nine times out of ten its bluffing games, but there are also other games that do it. There’s a lot we can learn from it, so let’s talk about it a bit.

Definition

The iocane powder problem, named after a famous scene from the classic film The Princess Bride, is a situation where players are forced to make a decision based on another player’s decision with very little else in the way. For example, in the film, the dread pirate Roberts and Vizini both have a cup, and Roberts decides to pour Iocane Powder (a poison) into one while the other isn’t looking. Vizini now must choose which cup to drink from. So the question is: is Vizini making a decision? He must decide which of the two cups to drink from, which you could argue is a decision no matter what, but not a meaningful one. If one were poisoned randomly, then his decision would be equally random. However, is the fact that Roberts knows which one is poisoned changing the nature of this decision? Is it a decision when it wasn’t before? That’s the problem.

Initial Depth

This problem mostly comes down to two very common design discussions. The first is what constitutes a meaningful decision. Usually this has to do with the results of the decision, but lets assume that the results are already assumed to be meaningful. The big thing is whether or not it is an informed decision. Is there any information you can use to make this decision. The answer is, theoretically, yes. This comes down to the other thing that people aren’t quite sure about: metagaming. If a player must choose between left or right, is there a predisposition? Do they pick right because they’re right handed? Do they pick left because they read left to right? It can’t quite be known for sure, but if you’re the player who has to guess what they picked, then that’s all you have to work with. So the decision is only meaningful if it’s an informed decisions, but it’s only informed if you can glean some information out of your opponent. But if your opponent is a good player, then they want to give as little information as they can, or preferably misleading information.

Yomi

Yomi is a Japanese term for the sort of battle of the minds I’m close to describing here. In Japan, some people consider a game as simple as Rock-Paper-Scissors to be a game of skill because of Yomi. It’s the idea that you can study your opponent and make plans around their plans. No two games are the same, and each game gives you new perspective into the next. This is especially trues when playing with the same opponent for an extended period of time.

Overthinking

However cool Yomi is, it’s not a given. Some people don’t have the skill or desire to pick up on subtle cues and gives. Not every game wants to be a duel. Even so, some players will get stuck trying to go through the motions when the game doesn’t support it. Or perhaps they’ll feel the need to when the game does it frequently enough or with a low enough payout that there’s no reason to. I think the Iocane Powder Problem is one that you should try to avoid.

Avoiding the Problem

There are two main ways to get around the problem in my opinion. The first is just to remove the choice. For example, if a player picks a card out of another players hand, force the player to shuffle their hand first. Don’t let the player sit there trying to read their opponents face or try remembering which card they draw that turn. The payoff is so minor and difficult that it’s better just to even the playing field and save everyone some time. The other option is to not make the first player’s choice meaningless. If the first player must choose between left and right, maybe the left will gain them health and the right will gain them money. Now the second player doesn’t have to think about whether they’re a lefty or a righty, they can just think about the much more apparent game statistics and what that player needs right now. If you make the benefit very minor, you can also make it a bit more entertaining. If they only get one health or one dollar, then maybe the player who needs money is willing to not take some if it means throwing off the other player. That’s much more engaging and entertaining then just staring down the other player and guessing.

Conclusion

Try to avoid these feedback loops between players in your games. As silly or fun as it can be the first time, having to do the back and forth of I know what you know that I know gets tiring. Also, makes rue to spot it when it happens. If you do, try one of the solutions above. Good luck!