If you have more than one face-down development card in Settlers of Catan, do you have to keep them distinguished?

Question

For example, if you buy a development card on turn 5, and then another one on turn 8, do you have to keep them distinguished?

When you play a card, if it was one you got more recently, it may be a clue that the other card is a victory point, since it hasn't been played. If you played the one you got a while ago, then there is no doubt what it is.

In all my games I've played, however, everyone just keeps them out in front of themselves, so it's not too hard to keep track if you pay attention.

I am building an AI for the game (to get some insights out of it, as well and possibly determine fairness of certain map configurations), and while this is a minor point, I would rather be technically correct when constructing the rules for the game, since I plan on using some degree of hand information to describe the board state for the AI.

Answer 1

The rules, section 3d, say "Keep your development cards hidden (in your hand) until you play them, so your opponents can't anticipate your play."

In games I've played people tend to stack cards in front of themselves rather than completely conceal them. Even so, long as they don't play a card on the turn it was purchased, there is nothing stopping them from stacking/ordering cards in whatever way they choose.

So, yes, players can certainly mentally keep track of how many development cards someone may have picked up, there is nothing requiring them to be visible to other players after that point.

Answer 2

I would say that knowing how many dev cards are held is an important and known factor. The times at which the player purchased dev cards would also be known - but should not be linked to the specific card. It is an option for the player to shuffle their Dev cards to keep this detail hidden. Therefore the AI could speculate on total time held but not be able to "know" for sure how long each individual dev card has been held for as part of a fair AI build.

Answer 3

According to the rules you can play 1 development card during your turn (with an exception to victory points which are revealed when you declare victory) as long as you did not purchase it this turn.

So you are not required to play it. Which means there is no guarantee that hidden development cards are victory points.

For an AI, you can make some educated guesses.

• At first it is always nice to play safe. So assume the hidden cards are victory cards.
• If a player has X hidden cards at the start of their turn and Y points (visible) and X+Y is enough to win, you can safely assume that at least not all of the X cards are victory cards, else the player should have revealed them.
• Note the total number of victory cards in the game.
• If a major resource of the player is blocked by the robber, and the player did not play a knight, you can assume he has no knights (although you can play with this).
• You can make simmilar assumptions for the other development cards.