Level 9 - Stalling

Conventions

Stalling Situation

• First, see the section on Minimum Clue Value Principle, one of our core principles.
• On most turns, players will not have any known-playable (or known-trash) cards. Thus, on most turns, player will either give a clue (if it is a good clue) or discard chop (the null action).
• However, in certain situations, discarding the chop card can be dangerous, having the potential to lower the maximum score. In those situations, the only safe action to perform is to give a clue. So, in those situations, we allow players to give low-value clues that would otherwise be illegal.
• We call these types of situations Stalling Situations. The rest of this page will go over the specific kinds of Stalling Situations that exist.

Allowable Stall Clues (Stall Table)

• In Stalling Situations, everyone understands that a player might be giving a low-value clue. However, there are limits - they are not allowed to just clue anything they want. These are the specific clues that they are allowed to give along with the precedence of each clue:

Precedence	Type of Clue	Normal Situation (Severity 0)	Early Game (Severity 1)	Double Discard / Scream Discard (Severity 2)	Locked Hand (Severity 3)	8 Clues (Severity 4)	End-Game (Severity ?)
1	Normal Play Clues or normal Save Clues	✔️	✔️	✔️	✔️	✔️	✔️
2	5 Stall (cluing off chop 5's)	❌	✔️	✔️	✔️	✔️	use context
3	Tempo Clue Stall (re-cluing a card to make it play)	❌	❌	✔️	✔️	✔️	use context
4 (tied)	Fill-In Clue (giving extra information to already-clued cards or Chop Moved cards)	❌	❌	✔️	✔️	✔️	use context
4 (tied)	Locked Hand Save (saving any card on chop, as long as doing so would not Lock the other player)	❌	❌	❌	✔️	❌	use context
4 (tied)	8 Clue Save (saving any card not on slot 1)	❌	❌	❌	❌	✔️	use context
5	Hard Burn (re-cluing a card that gives no new information, usually a 5)	❌	❌	✔️	✔️	✔️	use context

• Don't let this complicated table scare you: it is mostly describing some common-sense Hanabi intuitions.
• For example:
  • It is the Early Game (severity 1).
  • Alice does not have any normal Play Clues or Save Clues to give (precedence 1).
  • Alice does not have any 5 Stalls to give (precedence 2).
  • Alice does have a Tempo Clue to give (precedence 3), but Tempo Clue Stalls are not valid in the Early Game. Thus, if Alice gives a Tempo Clue, it would instead be interpreted as a Tempo Clue Chop Move.
  • Thus, since Alice does not want to cause a Tempo Clue Chop Move, she must discard.
• For example:
  • The team has 8 clues (severity 4).
  • Alice does not have any normal Play Clues or Save Clues to give (precedence 1).
  • Alice does not have any 5 Stalls to give (precedence 2).
  • Alice does have a Tempo Clue to give (precedence 3).
  • Thus, Alice must perform the Tempo Clue. It will be interpreted as a Tempo Clue Stall (and will not have a Chop Move component). Furthermore, Alice is not allowed to do any moves with precedence 4 or 5.
• What is the point in having a complicated precedence table? Normally, players in stalling situations are not able to give tricky-looking Finesses, because everyone else will think that they are just giving a stall clue. However, if it can be seen that there is a better clue available for them to give, then everyone can know that they are not giving a stall clue. So, because of this precedence table, players in stalling situations are still often able to make Finesses happen.

The Early Game (Severity 1 Stalling)

• The Early Game is introduced in the beginner's guide. In short:
  • The Early Game is defined as the period of time before any player has discarded their chop card.
  • Players must "extinguish" all of the available Play Clues and Save Clues before ending the Early Game.
• As an intermediate player, you need to know about a few extra rules about the Early Game. We don't bother telling the extra rules to beginners because they deal with some edge-case situations. We have the extra rules because we want to "squeeze" as much value out of the conventions as possible.

Ending the Early Game

• The Early Game is only ended when the first completely unknown card is discarded.
• In other words:
  • Misplaying a card does not count as ending the Early Game.
  • Discarding known-trash does not count as ending the Early Game.
  • Doing special discards that "transfer" cards to other players does not count as ending the Early Game.

Extinguishing Every Clue

• Extinguishing every clue does not include giving clues that would violate Good Touch Principle. (For example, if someone has two copies of red 1 in their hand, then the standard solution is to wait until one of the copies is discarded.)
• Extinguishing every clue does not include giving Tempo Clues (e.g. clues that do not meet Minimum Clue Value Principle).
• Extinguishing every clue does not include cluing cards that will be almost certainly be Order Chop Moved by an upcoming player who already has two or more 1's clued in their hand.
• Extinguishing every clue does not include cluing something in the hand of the player who came directly before. See the Permission to Discard section.
• Extinguishing every clue does include 5 Stalling, but it is only mandatory for the team to collectively perform one 5 Stall. If one 5 Stall clue has already been given and there is another 5 Stall clue available, players are allowed to clue it if they want, but they don't have to.

Permission to Discard (PTD)

• Normally, you have to "extinguish" every Play Clue and Save Clue before ending the Early Game.
• However, there are several exceptions, which are listed in the Extinguishing Every Clue section.
• The most important exception is that you are not required to clue the hand of the player who came directly before you. Players in this situation can clue the previous player if they want, or they can discard if they want - it's up to them.
• This is because if Alice does not see any Play Clues or Save Clues for Bob to give, then Alice is implicitly giving Bob Permission to Discard (or PTD for short).
• For level 11 players, note that Permission to Discard does not apply for Bob when Alice was blind-playing a card in a situation where Guide Principle applies.

Double Discard Situations / Double Discard Avoidance (DDA) (Severity 2 Stalling)

• Often times in Hanabi, two players will discard in a row. However, in rare cases, this can cause a perfect score to be lost.
• For example, in a 3-player game:
  • Alice has nothing to do. Alice discards her chop and it is a red 4.
  • Bob has nothing to do. Bob discards his chop and it is the other copy of the red 4.
  • Since both copies of the red 4 are discarded, it is no longer possible to get a perfect score. (The maximum score now is 23 instead of 25.)
  • Normally, someone on the team would give a Save Clue to Bob's red 4 before it could get discarded. But since Bob's turn was immediately after Alice's turn, no-one on the team had time to save it.
• In the previous example, on Bob's turn, since Bob could have the red 4 on his chop, we would say that Bob is in a Double Discard Situation for the red 4.
• More formally, a Double Discard Situation is defined as when:
  1. the previous player discards or misplays a card
  2. and the current player could be discarding the other copy of that card.
• Players agree to never discard in a Double Discard Situation if it has the potential to lower the maximum score. Instead, they must give some clue. This is called Double Discard Avoidance, or DDA for short.
• If a player in DDA has no normal Play Clues or Save Clues to give, then they are allowed to give "stall" clues, like a 5 Stall. If there are no 5 Stalls to give, they can even just "fill-in" some information on an already-clued card (and doing this should not be read as a Play Clue or a Finesse or anything like that).
• Let's revisit the above example to show what Bob should have done:
  • Alice has nothing to do. Alice discards her chop and it is a red 4.
  • Bob has nothing to do (meaning that there are no normal Play Clues or Save Clues to give). Bob also has a completely unclued hand.
  • Bob's chop is his slot 5 card. Since Bob does not see the red 4 in anyone else's hand and Bob's slot 5 card has no positive or negative clues on it, it is possible that Bob's slot 5 card could be the red 4. Thus, Bob knows that he is currently in a Double Discard Situation for the red 4.
  • Since there are no normal Play Clues or Save Clues available, Bob looks around to see if he can give a 5 Stall. Bob sees that Cathy has a red 5 on her slot 1, so he clues number 5 to Cathy as a 5 Stall.
  • Cathy knows that since Bob was in a Double Discard Situation for the red 4, she should not read too closely into his clues. This number 5 clue must just be a 5 Stall (as opposed to a Play Clue on the 5).

Locked Hands (Severity 3 Stalling)

• Generally speaking, it is a bad situation when someone's hand gets fully clued. This is also known as being Locked, and it should be avoided if possible. However, sometimes it cannot be helped, like when a player draws three 5's in a row.
• A player with a Locked Hand may give a low-value clue because they are not sure that they can play anything (and they can't discard because their hand is fully clued). Similar to a Double Discard situation, players should not read too closely into any clues given during this state.
• If the team is out of clues and someone's hand is fully clued, then you have to discard to generate a clue for them. Similarly, if there is only 1 clue left, you cannot steal it from them.

Clues Given While at 8 Clues (Severity 4 Stalling)

• At the beginning of the game, you start with 8 clues. This section only applies to situations where you climb to 8 clues in the middle of the game.
• A player who has a turn with 8 clue tokens available may give a low-value clue because they cannot play anything (and they cannot discard because the game does not allow you to discard while at 8 clues). Similar to a Double Discard or a Locked Hand situation, players should not read too closely into any clues given during this state.

Special Moves

The 5 Stall (Intermediate Section)

• As mentioned in the level 2, 5 Stalls are when a player clues an off chop 5 purely because they want (or need) to give a stall clue.
• 5 Stalls are usually performed in the Early Game. Less commonly, they can also be performed in the Mid-Game if a player happens to be in a special "stalling" situation where they are not allowed to discard.
• In the Early Game, the team can give as many 5 Stalls as they want before initiating the Mid-Game.
• Regardless of whether they are done in the Early Game or the Mid-Game, 5 Stalls are only allowed if there is nothing else "normal" to do (like playing a card, giving a normal Play Clue, or giving a normal Save Clue).
  • However, see the Finesse Position Exception section below.
• 5 Stalls must be given to the 5 that is closest to chop. For example, in a 3-player game:
  • It is the Early Game. The only thing left for Alice to do is to clue an off chop 5.
  • Bob has two playable 1's on slots 1 and 2. He has a green 5 on slot 4. Bob's 5 is therefore one-away from chop.
  • Cathy has nothing clued in her hand. She has a purple 5 on slot 3. Cathy's 5 is therefore two-away from chop.
  • Alice must clue number 5 to Bob as a 5 Stall since his 5 is closer to chop (even though Bob has two playable cards).

• When in the Early Game, there is an additional special rule for 5 Stalls.

The 5 Stall Finesse Position Exception (FPE)

• Normally, you are only allowed to perform a 5 Stall if:
  1. it is currently a valid Stalling Situation
  2. there are no normal Play Clues or normal Save Clues to give
• However, as an exception, players are also allowed to 5 Stall in Stalling Situations if there is only one Play Clue remaining to give and it would touch a card on Finesse Position that someone else on the team could possibly Finesse. We refer to this as the Finesse Position Exception, or FPE for short.
• The Finesse Position Exception applies if the same card is in multiple Finesse Positions and there is nothing else to do.
• The Finesse Position Exception applies whenever a player can perform a 5 Stall, regardless of whether it is the Early Game or the Mid-Game.
• The Finesse Position Exception only applies to 5 Stalls. Therefore, you cannot use the Finesse Position Exception as an excuse to end the Early Game.
• The Finesse Position Exception only applies when the playable card on Finesse Position can actually be Finessed or "gotten" by someone else. For example, it would not apply in a situation like this:
  • It is the Early Game and there is one clue left.
  • Alice sees that Bob has an unclued, off-chop 5.
  • Alice sees that Cathy has a unclued playable card on her Finesse Position.
  • Alice knows that in a hypothetical where she uses the last clue to give a 5 Stall to Bob, then Bob would be at 0 clues and would have to discard, and then it would be Cathy's turn, and then Cathy would either clue or discard.
  • In this hypothetical, it would get to Cathy's turn before anyone on the team had a chance to Finesse Cathy's Finesse Position card. Thus, the Finesse Position Exception would not apply. Subsequently, it would be illegal for Alice to perform a 5 Stall, so Alice must clue Cathy's Finesse Position card directly.

The Fill-In Clue

• A Fill-In Clue is defined as a clue that:
  1. only touches card(s) that already have a clue on them (or are Chop Moved)
  2. gives additional information to the touched card(s) that was not there before
• Fill-In Clues are only used in specific stalling situations - see the stalling table above for the specific situations that you are allowed to perform one. If you give a clue like this in a normal situation, it would just look like a Play Clue.

The Locked Hand Save (LHS)

• We agree that players with a Locked Hand gain the special ability to save any card they want on chop (as long as it would not Lock the other player). This is called a Locked Hand Save.
• A Locked Hand Save can be performed on any card, not just a critical or playable card.
• However, players can only do a Locked Hand Save if there are no higher precedence clues available. See the "Allowable Stall Clues" section above.
• A Locked Hand Save can be performed with either a color clue or a number clue.
• If a clue that looks like a Locked Hand Save would Lock another player, it is instead treated as a normal Play Clue or a normal Save Clue.
• Note that the precedence of a Locked Hand Save is tied with a "fill-in" clue. Essentially, this means that players who have a Locked Hand are not forced to perform a Locked Hand Save if they do not want to. Most of the time, doing a Locked Hand Save will be pretty good (as a 1-for-1 or a 2-for-1 instead of a 0-for-1), but Locked players can always ignore a Locked Hand Save to perform a "fill-in" clue if they want.

The Anxiety Play (Forcing a Locked Player to Play)

• Sometimes, someone with a Locked Hand has a playable card, but they do not know that they can play it yet. Re-cluing the card would signal this, but that would waste a clue and not be very efficient.
• A better way to signal this information is to deliberately leave them at 0 clues. By convention, this means that one of their cards is actually playable. The player should play the card in their hand that is most likely to be playable. If there is more than one option, then they should know that the leftmost is playable. (This follows from Leftmost Playable Principle.)
• This is called an Anxiety Play because you are putting the Locked player in a "do or die" situation.

The 8 Clue Save (8CS)

• We agree that players who have 8 clues available on their turn gain the special ability to save any card they want on or off chop (as long as it is not on slot 1). This is called an 8 Clue Save.
• An 8 Clue Save can be performed on any card, not just a critical or playable card. However, players can only do an 8 Clue Save if there are no higher precedence clues available. See the "Allowable Stall Clues" section above.
• An 8 Clue Save can be performed with either a color clue or a number clue.
• If a clue that looks like an 8 Clue Save is on a card that is on slot 1, it is instead treated as a normal Play Clue or a normal Save Clue.
• The 8 Clue Save does not apply on the first turn of the game.