Part 1 - Play Order Inversion in the Starting Hand
If one or more 1's in your hand are clued, you should assume that they are all playable. (This only applies to 1's, and follows from Good Touch Principle.)
We agree that playing 1's at the beginning of the game is a special case - you should always play the 1's in your starting hand from oldest to newest. (This is a special case because normally, Play Clues mean to play the leftmost card.)
In the below example:
On the first turn of the game, Alice clues number 1 to Bob, which touches three 1s (on slot 2, slot 3, and slot 4).
From Good Touch Principle, Bob knows that he can now play all three of these cards.
Bob should play the slot 4 card first, and then the slot 3 card, and then the slot 2 card.
The previous section applies when all of the clued 1s were present in the starting hand. In other words, if one or more 1s are clued that were not in the starting hand, then you would play them as normal from left-to-right.
However, what if there is a mix of staring hand 1s and non-starting hand 1s? Then, things get a little more complicated.
In this situation, we call the non-starting hand 1s "fresh" 1s. It makes sense that fresh 1s would be more important than non-fresh 1s, because otherwise the non-fresh 1s might have been clued earlier.
Thus, freshly drawn 1's should always be played before non-fresh 1's.
Continuing on from the example in the previous section, imagine that:
Bob plays his slot 4 card. It is a red 1 and it successfully plays. (He then draws a card, and all of the other cards in his hand slide over.)
Alice clues 1's to Bob, which touches a new card on slot 1 and re-touches the ones on slot 3 and slot 4.
Bob knows that fresh 1's have precedence, so he plays the slot 1 card next.
After that, Bob resumes the play order from before, playing the slot 4 card, and then the slot 3 card.
The Fresh 1's Rule has an exception: Chop-Focusoverrides it.
For example, in a 3-player game:
Red 2 and blue 2 are played on the stacks.
Alice discards a red 4.
Bob clues number 1 to Alice, touching four 1's on slots 1, 2, 3, and 5.
Alice knows that the correct order to play all of the 1's in is 5, 1, 3, 2:
Alice knows that normally, you are supposed to play freshly-drawn 1's before 1's that were present in your starting hand. However, Chop-Focus overrides this rule, so she knows that the slot 5 card (her chop) should play first.
After that, she uses the Fresh 1's Rule, and knows to play the 1 in slot 1 next.
After that, she will play the rest of the 1's from oldest to newest (since they were in her starting hand), so she will play slot 3 and then slot 2.
Nearly every clue is either a Save Clue or Play Clue. One exception to this is a Fix Clue, which is an attempt to "fix" a violation of Good Touch Principle.
Fix Clues are often needed when a duplicate card is touched. Cards are not normally duplicated (which follows from Good Touch Principle), but sometimes a mistake is made, or a sequence of particular cards makes duplicating necessary. Duplicate cards will lead to misplays, so it is the team's responsibility to fix the problem and intervene before this happens.
In general, violations of Good Touch Principle should be fixed as soon as possible, regardless of whether the misplay happens immediately or not.
In the example below:
Before the clue was given, Bob had an unknown purple card in his hand.
Alice knows that from Good Touch Principle, Bob will conclude that the card is a purple 5, and he will likely misplay it on his next turn.
Alice clues number 3 to Bob, which "fills in" the purple card and reveals that it is purple 3.
Since Bob was about to play this card, Bob knows that this was a Fix Clue and that he can now safely discard the purple 3.
A clue cannot be a Play Clue and a Fix Clue at the same time. If you receive a Fix Clue and it touches other ancillary cards, none of them are necessarily playable. The only information that a Fix Clue conveys is to fix the violation of Good Touch Principle.
In the example below:
Before the clue was given, Bob has an unknown 1 in his hand.
Alice knows that from Good Touch Principle, Bob will conclude that his 1 is a green 1, and he will likely misplay it on his next turn.
Alice clues blue to Bob, which "fills in" the 1 and reveals that it is blue 1. The blue clue also touches a blue card on slot 1.
In this situation, Bob might be tempted to think that this is a Play Clue on a blue 2 in slot 1, especially considering that the slot 1 card was the only new card introduced in the clue. (And the focus of a clue should always be on the new card introduced.)
However, the fact that the blue clue "fixed" a violation of Good Touch Principle means that Alice may have had no choice but to clue blue, and she may not necessarily be trying to give a Play Clue.
Bob marks the blue card on slot 1 as either blue 2, blue 3, blue 4, or blue 5. He then discards the blue 1.
The Fix Clue (That Gives No Additional Information)
Usually a Fix Clue will "fill in" the card to explicitly make it known that the card is unplayable or duplicated. However, it is also possible to perform a Fix Clue just by cluing the card again.
In the example below:
Alice clues Bob number 1 and it touches three 1's.
Bob successfully plays two 1's.
Alice clues Bob number 1 again, and all the clue does is re-touch the remaining 1.
Since Bob was going to play the 1 already without Alice doing anything, the clue must have some other meaning. Thus, it is a Fix Clue: the remaining 1 is bad, and Bob can safely discard it.
Fix Clues that give no additional information only "fix" one card.
In the example below:
Alice clues Bob number 1 and it touches three 1's.
Bob successfully plays one 1.
Alice clues Bob number 1 again, and all the clue does is re-touch the two remaining 1's.
Since Bob was going to play his 1's already without Alice doing anything, the clue must have some other meaning. Thus, it is a Fix Clue: the 1 that Bob was about to play is bad, and Bob can safely discard it. Bob skips over the 1 that he was about to play (on slot 4) and plays the other one (on slot 3).
Most of the time, a Fix Clue is given by retouching the card that needs to be fixed in some way. Rarely, it is also possible to give a Fix Clue by "filling it in" with a negative number clue.
In the example below:
Red 4 and blue 2 are played on the stacks.
Before the clue was given, Bob had an unknown blue card in his hand and Cathy had a blue 3 and blue 4 already clued in her hand.
Alice know that from Good Touch Principle, Bob will conclude that his clued blue card is a blue 5, and he will likely misplay it on a future turn.
Alice clues number 5 to Bob, which touches a brand new 5. But it also falsifies the "blue 5" note that Bob has written on his blue card.
Bob might be tempted to consider this a Play Clue on the focused 5. (Red 5 is currently playable, so it might be a playable red 5.)
However, Bob knows that since the clue prevented a misplay, it is not necessarily a Play Clue. Thus, Bob has to keep the 5 in his hand until he gets more information.
Occasionally, through a mistake (or complicated situation), the same card will be clued in two different people's hands. Generally, this is to be avoided, but sometimes it happens. Handling this can be tricky.
Generally, the first player who fully realizes that they have the duplicate card should discard it (as opposed to playing it or holding on to it). This is called a Sarcastic Discard, and it communicates to the other player that they 100% have the discarded card. (This is because normally, from Good Touch Principle, we never discard cards that have been clued, so if a player discards a clued non-trash card, something special must be going on.)
For example, in a 3-player game:
Red 2 is played on the stacks.
Alice has one red 3 clued in her hand with just number 3. (She does not know which suit it is.)
Alice clues number 3 to Bob, which touches one 3. (This is a mistake, because it might be violating Good Touch Principle.)
Bob knows that the only playable 3 is red 3. He also knows that Alice has a clued red 3 already in her hand. Thus, he knows that he has the red 3 and that Alice made a mistake.
Bob performs a Sarcastic Discard to pass the red 3 back to Alice.
The Sarcastic Discard is similar to the Prompt, except that it is initiated by a discard instead of a clue.
However, unlike a Prompt, if there are multiple cards that a Sarcastic Discard could apply to, then it does not promise that it is the leftmost card. It only promises that they have the card somewhere. For example:
Alice Sarcastic Discards a red 3.
Bob has two cards clued with number 3 in his hand. He does not have any color information on either 3.
Bob can be certain that one of the two 3's is red 3, but he does not know which one it is yet.
On a turn where a player misplays and accumulates a strike for the team, they could have discarded instead and generated a clue.
So, if you can spend one clue to stop one misplay, the value comes out even.
Thus, since there are only 2 strikes allowed and accumulating strikes limits flexibility, it is almost always worth it to spend one clue to stop one strike.
If it would require two clues to stop an impending misplay, then as long as the strike would not lose the game, it is usually best to let the player misplay the card and get a strike.
A big part of Hanabi is of trying to be as efficient as possible. This means that players will generally try to "get" as many cards with one clue as possible.
If you use one clue to get one card, we refer to that as a 1-for-1 clue. For example:
On the first turn of the game, Alice clues Bob number 1, touching one 1 as a 1-for-1.
If you use one clue to get two cards, we refer to that as a 2-for-1 clue. For example:
On the first turn of the game, Alice clues Bob number 1, touching two 1's as a 2-for-1. (Bob will play both.)
3-for-1 clues are even better than 2-for-1 clues, and so forth. It is even possible to perform a 9-for-1 clue with advanced techniques.
If a clue touches two cards but only one of them will play right now, it still counts as a 2-for-1. This is because we assume that all touched cards will eventually play from Good Touch Principle. For example:
On the first turn of the game, Alice clues Bob red, touching a red 1 on slot 1 and a red 5 on slot 2 as a 2-for-1. (Bob will only play the red 1 and save the other red card for later.)
On Hanab Live, the future required efficiency is shown on the right side of the screen. Future required efficiency is calculated by the following formula:
number of cards that remain to be clued / number of clues remaining
If future required efficiency is high, players should probably not perform 1-for-1 clues! Instead, it is better to discard and try to let someone perform a Finesse.
Tempo is a term used to describe the speed at which cards are played. (This is similar to how it is used in other games such as chess.)
Hanabi can be thought of a race to get all the cards played before the time runs out. This means that even if the team is being extremely efficient, they can still lose the game if they are not playing their cards fast enough. Thus, players have to balance Efficiency and Tempo. You can think of Efficiency and Tempo as the yin and yang of Hanabi.
At the beginning of the game, there is a lot of time left, so players will generally prefer clues that get a lot of Efficiency over clues that get a lot of Tempo.
At the end of the game, there is almost no time left, so players stop caring about Efficiency and start only caring about Tempo.
On Hanab Live, "Pace" is shown at the right side of the screen. Pace is a measure of how many more discards can occur, so this essentially tells you how much time is left in the game. Starting pace is calculated by the following formula:
current score + cards in deck + number of players - maximum score
Note that even at the beginning of the game, players might prefer a clue that gets Tempo over a more efficient clue. For example, they might value Tempo because it would prevent the discard of some other useful card. It all depends on the context of the game!
As soon as a clue is given to a card, if it is enough to determine the card's full identity, then the assumed identity is said to be locked in to the card. (On Hanab Live, this is usually represented as a player writing an "identity note" on the card.)
For example, in a 3-player no variant game:
It is the first turn and nothing is played on the stacks.
Alice clues red to Bob, touching a red card on slot 1 as a Play Clue.
Bob looks at Cathy's hand, her Finesse Position (slot 1) is not red 1, thus this is not Finesse.
Bob immediately right-clicks on the card and writes a note of "red 1".
This card is now "locked in" as a red 1. No future clues or actions from other players can ever change that.
A superposition is a term from quantum mechanics that describes how something can be two different things at the same time. For example, an electron is a type of a particle, and an electron can be "spin up" or "spin down". But an electron could also be in a superposition of both "spin up" and "spin down" at the same time, as weird as that sounds. If an electron happens to bounce off of something (i.e. is measured), then the superposition will "collapse" and it will only be in a "spin up" or "spin down" state. The details of quantum mechanics are not important - the point is that we treat unknown Hanabi cards sort of like unknown particles: even though they really have a true identity, we ignore that and treat them as being all of the possibilities at the same time.
Even though it does not matter for the purposes of Hanabi, you should know that the electron analogy is bad because electrons do not actually have a true identity. But just roll with it for now.
As soon as a clue is given to a card that could be two or more different things, then the assumed superposition of all of the possibilities is locked in to the card.
For example, in a 3-player game:
Red 1 and blue 1 are played on the stacks.
Alice clues number 2 to Bob, touching a two on slot 1 as a Play Clue.
Bob looks at Cathy's hand. Cathy's Finesse Position is not a 1. Thus, this is not Reverse Finesse.
Bob writes a card note of "red 2 or blue 2" on his clued card.
This card is now "locked in" as this specific superposition. Future clues and actions can narrow down the cards in the superposition or completely collapse the superposition, but new cards can never be added to the superposition.
A direct conflict is the only thing that can "break" an information lock.
For example, in a 3-player game:
Bob has a card in his hand that is touched with a number 2 clue. (It has no color clues on it.)
Bob has a written a note of "red 2" on the card, meaning that it has been "locked in" as a red 2. (Bob will permanently think that it is a red 2.)
Alice clues blue to Bob, which "fills in" the card as a blue 2.
It is now impossible for this card to be a red 2 - Bob knows that he was lied to earlier on in the game. Bob erases his note of "red 2" on the card and the Information Lock is broken.