We first discuss 3-player games before discussing 4/5-player games, variants, and convention proposals/discussions.
Optional Learning Path (click to open)
Level 0: Play a 2-player game with the variant 4 Suits. Only stable clues are required.
Level 1: Play a 3-player game of No Variant with the simplified targeting priority in Cathy's hand: play leftmost playable > play leftmost one-away > discard leftmost trash or same-hand dupe.
Level 2: Play a 3-player game of No Variant with the standard targeting priority in Cathy's hand.
Level 3: Play a 3-player game of Omni (5 Suits). Familiarize yourself with pink promise for play clues and locks and the fact that lock has precedence over playable rank in pinkish variants.
Level 4: Play a 4-player game. Learn the targeting priority in Donald's hand, how to compute finesses dependencies in Bob's hand and Cathy's hand. (If Donald has a one-away card, it is almost impossible to make Donald discard. Learn the discard re-targeting convention.) Different-hand dupes are much more common in 4-player games.
Level 5: Play a 5-player game. Learn the targeting priority in Emily's hand and continue finding dependent targets for finesses and following the discard re-targeting convention for targets in Donald's and Emily's hand.
ReactorZero uses the following terminology to describe the status of cards.
Card status (click to open)
A card is visible by a player if it appears in someone's else hand, in the discard pile or in the stacks or if it has full empathy. A card has full empathy if its empathy is reduced to only one card and does not contain any crosses.
Playable cards are cards that can play immediately on the stacks. Playable cards can be:
Playable-by-empathy: card's empathy, given by all combinations of ranks and colors visible on the card by pressing spacebar, only contains playable cards. For simplicity, only consider possibilities crossed out in the empathy by cards visible by all players (global empathy).
Playable-by-signal: known to be playable by being play-signaled
Obviously playable: playable-by-empathy or playable-by-signal.
Playable-by-good-touch: Same as playable-by-empathy except that the card's empathy may also contain trash cards. Cards visible by the clue giver are additionally taken into account to determine which crosses are known for playable rank clues.
Trash cards are cards whose empathy only contain cards that cannot become playable in the future. A same-hand dupe is a card whose second copy appears in the same hand.
ReactorZero has only two types of clues: stable and reactive. Every clue given to the next player is stable.
We name the player whose turn it is Alice and the subsequent players Bob, Cathy, Donald, Emily, and Fred.
Play reveal: Any stable clue that touches a card and makes it become playable-by-empathy merely tells Bob that he may play that card.
Otherwise, the meaning of a stable clue depends on what the clue was:
Clue type
Meaning
Color (touching new cards)
Play leftmost newly-touched card
Rank (touching new cards)
Discard the first unclued card to the right of the leftmost newly-touched card
Reclue with rank or color (touching no new cards)
Play leftmost touched card
Rank clues that touch new cards have different meanings in specific cases. In order of priority:
Playable rank: If the leftmost newly-touched card is playable-by-good-touch, play it.
Trash reveal: If the clue reveals a trash card (or a same-hand dupe) or you already had a trash card (or a same-hand dupe), discard the revealed trash or the trash you already had.
Lock: If the clue touched the rightmost unclued card, the recipient is locked.
A locked player may not discard any card until they receive a safe action.
An unlocked player, without a known or signaled action (play or discard), may discard their leftmost unclued card (their "chop") instead of giving a clue.
Stalling: If a card that was called to play is not immediately playable, the clue has no meaning beyond the information it provided to the hand.
For a summary on stable clues, follow this flowchart.
Every clue not given to the next player is reactive. (All of Alice's clues to anyone not Bob are reactive.)
For a reactive clue, the clue recipient is called the receiver; every player whose turn is after the clue-giver up to the recipient is called a (the) reactor.
The clue gets an action from the reactor(s) followed by an action from the receiver. When Bob takes that action, we say that Bob "reacts" to the reactive clue.
The type of action (discard or play) in both hands is determined by the type of clue:
Clue type
Meaning
color
odd number of plays from the reactor and the receiver (1 discard + 1 play, or 1 play + 1 discard)
rank
even number of plays from the reactor and the receiver (2 plays, or rarely 2 discards)
The value of a reactiverank clue is the numerical value of the rank clue. For example, if the clue was a rank 3 clue, the clue value is 3.
The value of a reactivecolor clue is red = 1, yellow = 2, green = 3, blue = 4, purple = 5. With additional colors, colors should be assigned missing values. If no colors are missing, start back from 1.
In order for Bob to know which action he should take, Alice and Bob need to agree on which action Cathy should take. This is achieved by the following targeting priority.
Targeting priority in Cathy's hand:
Play leftmost non-obviously playable card
Play leftmost obviously playable card
Play leftmost one-away card as a Bob-Cathy finesse
Discard leftmost trash or same-hand dupe
Discard leftmost different-hand dupe
Discard ("sacrifice") furthest-away from playable (tie-break: highest > leftmost)
Important notes (click to open)
Obviously playable: Whether a card is obviously playable is determined before the reactive clue is given.
Immediately playable: When Cathy is signaled a play, the targeted card in Cathy's hand must be immediately playable after Bob reacts.
Re-targeting: If the clue does not work (makes an unplayable card play or a critical card discard), the target is moved to the next possible target in the priority list. To compute the next possible target, consider what card would be prioritized if the impossible targets are ignored.
Clarifications (click to open)
Plays (priority 1, 2, 3):
A clued/signaled copy of a playable/finessable card does not take precedence over an unclued copy.
A unknown dupe is targeted before its playable-by-signal copy.
Finesses (priority 2): Only possible with rank clues as they require two plays.
Dupes (priority 4,5):
A dupe is a card whose second copy is visible to Alice
and all the reactors positioned before the hand containing the dupe.
Leftmost Trash (priority 4):
The leftmost trash in Cathy's hand is targetted no matter whether it had a prior discard signal or not.
Sacrifice (priority 6): To compute the furthest-away from playable, look only at the distance between each potential target and their corresponding stack. If multiple cards are furthest-away and equally far away, choose the card with the highest rank. If some of these have the same rank, choose the leftmost card. Moreover, do not sacrifice/target critical cards!
The leftmost touched and globally revealed card given by a stable clue.
A card called to play by a stable clue: direct color play clue, playable rank, or a reclue.
A card called to play by a reactive clue.
To avoid desynchronization, cards gotten by playable rank clues, whose playability relies on cards that are not visible by some players, are not considered play-signaled.
Play signals are not generally erased if the play-signaled card might have been duped. If it is deducible (by considering all the possibilities this card could have been when it was signaled) that the play-signaled card has been duped, the player marks that card as trash.
Fixing play signals (click to open)
Play-signaled cards that were actually duped can be fixed by:
A reactive discard signal to the play-signaled card.
A stable discard signal to the play-signaled card.
A stable clue touching the signaled card to reduce the possibilities (from the point of view of every player) this card could have been to only trash cards. In that case, the stable meaning of the clue should be ignored.
A player without playable cards can discard the card with the most recent discard signal. If no cards have discard signals, they can discard their leftmost unclued card ("chop").
After a player plays or discards a card or receives a lock clue, they erase all discard signals in their hand.
A player with multiple trash cards typically discards them from left to right.
Discard of cards without discard signals do not have any special meaning beyond giving a clue back to the team. They can exceptionally be done to generate a clue.
Hard information is any information that comes from the empathy of the cards. Soft information also includes pink promise and the possible identities of a play-signaled card (without taking into account targeting priority).
The meaning of a clue can only be overriden by hard information.
It is not expected that players deduce any information beyond soft information. These extra deductions are called contextual information (targeting priority, elimination notes, not given clues, ...). Players should in general refrain from taking any action (play/discard) from contextual information.
It is Alice's job to save Bob's chop. Alice assumes that Bob might discard their chop (if Bob does not have a safe action) even if there is a critical card on Cathy's chop.
Positional discards are only possible in endgame and get the last possible player to play the matching slot. A card gotten by positional discard is not considered play-signaled.
A positional discard is not always possible, e.g. if it would look identical to discarding chop. Assume generally that Alice is discarding her leftmost locally known trash over a positional discard.
At pace 0, everyone must play a card on the last round to achieve the maximum score; at pace x, x players don't have to. The players should try their best to avoid lines that do not get maximum score. Reactive clues that loses on the spot may be reinterpreted to satisfy that condition. Playing a card from context might also be necessary.
Cards are targeted as if there would be more turns to play. If a hand has less than the maximal amount of cards, the slot numbers are counted from left to right starting at slot 1.
¶ What happens if a reactor bombs or discards a critical card?
The next player must ignore the reaction and proceed as if they were locked for that turn. The entire reaction chain is off including the reactor and the reactor should not try to correct their mistake by reacting later.
¶ What happens if the receiver bombs or discards a critical card?
The targeted card is no longer considered signaled.
While receivers occasionally delay their actions, only rarely should reactors delay.
Details (click to open)
The receiver can delay their action by giving a clue or by playing a different card. In this case, the targeted card in the receiver's hand is signaled.
A reactor can delay their action by giving a clue, but in this case, the signal to later players is lost (e.g. Cathy does not try to figure out what was the meaning of the clue when Bob reacts later).
The reactor marks their card and is expected to react to the clue later, but the reactor's card is not considered signaled for targeting purposes.
When a player delays with a play-signaled card, it is mandatory for that player and the player positioned before them to remember/mark all playable possibilities for that card (omitting targeting priority inferences). This information should be used later to determine if the card is still playable, became trash or needs a fix.
Only the most recently given reactive clue, if there are multiple reactive clues given before your turn, is "active".
This section is only applicable when playing a game with special suits. For more on variants, see the variants page.
If there are muddy cards (excluding Muddy-Rainbow-Ones), a stable red color clue that touches the rightmost unclued card is a lock.
If there are brown cards, a stable brown color clue that touches the rightmost unclued card is a lock.
If there are null cards (excluding Null-Ones, including Brown-Fives), stable no-info clues to Bob are also considered locks. A no-info clue is a clue that does not give any new positive information to any card in Bob's hand.
In variants including a pinkish variants (Omni, Pink, Light Pink, Chimneys, Funnels)
locks have precedence over playable ranks.
pink promise for locks: if the rightmost unclued card can be clued with multiple ranks, its true rank (if available) must be used when locking. This information is used to determine the status of a card (e.g. trash, playable-by-signal).
pink promise for rank reclues, playable ranks and stalls: the true rank of the card that is called to play (focus) must be used (if available) when cluing cards touched by multiple ranks. This information is used to determine the status of a card (e.g. trash, playable-by-good-touch, playable-by-signal). If it can be deduced from the card's (global) empathy that the true rank was not used, the clue is assumed to be a stall.
pink promise does not apply to referential discard clues.
Playable rank for pinkish special fives (Omni-Fives, Pink-Fives, Light Pink-Fives). To determine if a clue is a playable rank clue, assume that the card that is called to play is not a 5 unless it can only be 5 or trash.
In Sudoku or Up or Down, the "highest" tie-breaker for sacrifices is not applied. Furthest-away is computed relative to all possible starting cards and taking the one that makes that card the least further-away before the clue was given.
In Reversed, the tie-breaker "highest" for sacrifice is computed relative to the stack starting card.
With an Inverted suit, a stable color clue to an inverted card means to attempt to play it (i.e. effectively discarding it).
For a card to be playable-by-empathy or known trash, the player must know whether it is inverted or not.
Playable rank applies to card playable-by-good-touch even if the drag direction is unknown. To decide on which direction to drag, assume that the leftmost newly touched card is an non-inverted card unless it can only be an inverted card or a trash card.
Reactive clues, rank = even number of attempted plays and color = odd number of attempted plays.
On hanab.live, to attempt to play an inverted card, drag it to the stacks: the card will discard. To attempt to discard an inverted card, drag it to the trash: it will play.
In Synesthesia, a reactive (color) clue is always even number of discards (i.e. generally maximum number of plays). A color clue that touches the rightmost unclued card it is a lock. Optionally, disable finesses.
For Alternating Clues, a color clue that touches the rightmost unclued card is a lock.
Alice's clues to Cathy are reactive like in a 3-player game. Since each hand contains 4 cards in a 4-player game, the equation involving the clue total is changed to
All clues to Donald are double reactive. They get an action from Bob (the first reactor) followed by an action from Cathy (the second reactor) followed by action from Donald (the receiver).
Clue type
Meaning
color
odd number of plays (3 plays or rarely 1 play)
rank
even number of plays (2 plays or very rarely 0 plays)
Targeting priority in Donald's hand (click to open)
Play leftmost non-obviously playable
Play leftmost obviously playable
Play leftmost one-away card
Play leftmost two-away card
Discard leftmost trash or same-hand dupe
Discard leftmost different-hand dupe
Discard furthest-away from playable (tie-break: highest > leftmost)
The target in Donald's hand is fixed before determining targets in other hands.
For targeting purposes, the status of cards in Donald's hand (playable,one-away,etc) is determined before any reaction occur (see discard re-targeting). For example, as Cathy, a one-away card in Donald's hand remains a one-away card even if Bob's reaction makes it playable.
If Donald's target is an X-away card, Donald's target forces connecting targets in other hands to make Donald's finesse work. The connecting target(s) is(are) assumed to be the leftmost copy on the latest player(s).
The clue is then reduced to a reactive clue between hands with unassigned targets.
Discard re-targeting (click to open)
Re-targeting refers to changing the card you target.
A play target is a card that would be signaled to play. This includes X-away cards. A discard target is a card that would be signaled to discard.
A card in a hand H that has just been targeted by the current clue prevents targets of the same suit from being play targets in hands occuring before H. Skipping over these blocked targets does not constitue re-targeting.
Do not re-target a play target for another play target to the right in any hand except Cathy's hand. If the clue does not work (makes an unplayable card play or a critical card discard) or if there are not enough plays remaining to make the target play as a finesse, try re-targeting on Cathy. If no re-targeting on Cathy make the reciever play their targeted card, change the reciever's target directly to the discard target with highest priority.
When re-targeting, preserve in priority the targets of the player that are the furthest-away from you.
A playable different hand-dupe is considered playable. As an exception, the card has the same priority as trash cards if its copy has just been play-signaled by the current clue in the hand of a later player.
All clues to Emily are triple reactive. They get an action from Bob (the first reactor) followed by an action from Cathy (the second reactor) followed by action from Donald (the third reactor), followed by an action by Emily (the receiver).
Clue type
Meaning
color
odd number of plays (3 plays or very rarely 1 play)
rank
even number of plays (4 plays or rarely 2 plays or almost never 0 plays)
Targeting priority in Emily's hand (click to open)
Play leftmost non-obviously playable
Play leftmost obviously playable
Play leftmost one-away card
Play leftmost two-away card
Play leftmost three-away card
Discard leftmost trash or same-hand dupe
Discard leftmost different-hand dupe
Discard furthest-away from playable (tie-break: highest > leftmost)
The target in Emily's hand is fixed before determining targets in other hands.
For targeting purposes, the status of cards in Emily's hand (playable,one-away,etc) is determined before any reaction occur (see discard re-targeting). For example, as Cathy, a one-away card in Emily's hand remains a one-away card even if Bob's reaction makes it playable.
If Emily's target is an X-away card, Emily's target forces connecting targets in other hands to make Emily's finesse work. The connecting target(s) is(are) assumed to be the leftmost copy on the latest player(s).
The clue is then reduced to a reactive clue between hands with unassigned targets.
This space is reserved for optional conventions and proposals so they can be referred to before the game.
(color=xy): The color totals may be changed pre-game. E.g. in a variant with two possible color clues, agreeing color=34 would mean the leftmost color has value 3 and the 2nd-leftmost, 4. Extra colors/ranks (such as rank 5 in a 4-player game) maybe be assigned a different meaning.
(switch): For reactive clues the roles of rank and color are switched.
(slot 1 finesse priority): Prioritize slot 1 on the reactor's hand over leftmost on the reciever's hand.
(ptd): Alice is not allowed to discard if Bob does not have a safe action and Bob's chop is playable or critical. Alice determines if Bob has a safe action and if Bob's chop is playable at the moment Zelda (the player before Alice) took her action. This means that if Zelda plays the same card as Bob's chop, Alice does not have PTD unless Alice can determine that Zelda knew about her card.
(endgame stable): In endgame, a play clue to any player is considered stable. If the play clue can be given with both color or rank, color is stable and rank is reactive.
(zscp): zero clue state promise from referential sieve.
(obv=non-obv): Drop the distinction between obviously playable cards and non-obviously playable cards.
(advanced targeting): inbetween + connecting + max
(inbetween): playable cards on inbetween players have priority over a finesse involving you.
(connecting): if the play target in the reciever's hand (without re-targeting) became playable (or has its distance to playability reduced), target that card over a play in your own hand.
(max): allow re-targeting on any players to get the maximum amount of plays (if the default meaning of the clue does not get max plays). If multiple interpretation are possible re-target on the players closest to you in priority. To determine if a re-targeting would work on later players, assume no assymetric information except on the identity of the card that you are playing.
(syn-stable-rank): In Synesthesia, all stable clues behave like a rank clue instead of being stalls. For example, touching rightmost unclued card locks and reclues gets the leftmost card to play. Good-touch for cards with two color clues still applies.
(drag right): With an Inverted suit, a stable color clue to an inverted card tells the focus to drag right.
(max rank): rank = even number of discards, color = odd number of discards.
(max color): color = even number of discards, rank = odd number of discards.
(referential play clues): stablecolor clues (touching new cards) mean play the first unclued card left of the leftmost newly-touched card, pretending the clue didn't touch slot 1; if it touched slot 1 only, play the rightmost unclued card
(focus inversion): make stablecolor clues play the first possible card from left to right (i.e. re-target instead of stalling if the leftmost colored card is not playable)
(slot for color/rank): the value of a reactive clue is the slot number of the leftmost touched (newly or not) card, ignoring slot 1; if slot 1 is the sole slot touched (newly or not), the value is 1
(delayed plays): allow stable delayed play clues if someone has a globally known card
(prompts): Make a play-signaled card play through clued cards. If there are not enough clued cards, the clue is just a stall. Play reveals > prompts. Useful for 2-player.
(sarcastic on playable): discarding a known playable card promises that the card is clued in an other player's hand. If no matching cards are clued, nothing is promised. Useful for 2-player.
(good touch for 1s): 1s plays on their own by good-touch from left to right. Fix 1s by giving a stable color clue just before it bombs (the clue is just a fix). Useful for 2-player.
2025/11/29: Allow re-targeting over X-away targets blocked by a targeted card of the same suit on a later player within the same clue.
2025/11/26: New stable clue flowchart that is native and does not require login
2025/11/15: Change to Synesthesia convention allowing stable color clues.
2025/11/13: Discarding a critical card has now the same effect as a bomb for recovery purposes.
2025/11/09: Pink play lies are stalls (if deducible from "global" empathy).
2025/10/31: Pink promise conventions do not apply anymore to pinkish special-ones and special-fives. Playable rank for pinkish special-fives.
2025/10/29: Responsibility for remembering possibilities for a play-signaled card that was delayed.
2025/10/29: Add convention for bombing receiver.
2025/10/22: Renamed playability categories
2025/10/21: Change how playable rank clues work with an inverted suit.
2025/10/21: Change how playable rank clues work with special pinkish suits.
2025/10/20: Add special conventions for Inverted and Synesthesia.
2025/10/07: When fixing a play-signaled card with a stable clue, the meaning of the stable clue is now ignored.
2025/10/01: Added suggested learning path.
2025/09/26: Remove Maximum Play exception to Re-targeting.
2025/09/26: Revert to simple targeting priority in the receiver's hand. Cathy's play does not have priority over B-D finesse anymore.
2025/09/25: Simplify playable dupe exception: playable dupe considered playable unless it has just been played signaled in a later player's hand as part of the reactive clue.
2025/09/21: Change to targeting priority: playable-by-signal cards are now prioritized over X-away cards in all hands. Remove Inbetween priority.
2025/09/17: Add Maximum Play exception to Re-targeting.
2025/09/12: Define dupe and introduce different-hand dupe priority for 3-player games, to be consistent with games with more players.
2025/09/10: Add No Context and Best Effort sections for clarification, as well as more optional conventions
2025/09/07: Remove Connecting Principle and add No Finesse Re-targeting
2025/08/30: Update Connecting Principle
2025/08/25: Update Delay Convention, Inbetween Priority and Connecting Principle
2025/08/24: Define which cards are play-signaled.
2025/08/24: Play reveals that are not global do not override the meaning of a stable clue anymore. For example, a playable rank clue locally revealing a card still gets the leftmost card.
2025/08/23: Simplfied definition of global knownledge.
2025/08/22: Conventions for 5-player
2025/08/22: Add Cathy's playable priority levels in 4-player priority table.
2025/08/21: Make "play reveal" have top priority.
2025/08/20: Locks now have priority over playable rank (in pinkish variants)
2025/08/17: Use highest before leftmost as a tie-breaker for sacrifice.
2025/08/17: Conventions for 4-player (target playable-by-signal before finesses in Cathy's hand, different hand dupe, cathy connecting principle)
2025/08/14: Playable rank reformulated as good-touched rank.
2025/07/19: Remove different hand dupe for 4-player or more.
2025/07/17: Added playable rank clues.
2025/07/05: Different hand dupe priority for 4-player or more.
2025/07/05: Emily’s priority for 5-player games
2025/07/05: Simplified finesses in 4-player games
2025/07/04: Add pink promise for play clues
2025/07/04: Change back order of discard from left to right
2025/07/04: Remove queued plays (playable card must be immediately playable and can be played in any order)
2025/07/04: Use playable reveals as stable clues.
2025/07/04: Change stable discard to ref sieve style.
2025/07/04: Move leftmost playable-by-signal above leftmost trash in the priority list.
2025/07/04: Change order of discards to right to left.
2025/07/04: Add pink promise on locks.
2025/07/04: Add endgame positional discards.
2025/07/04: Change stable clues to direct stable clues.
2025/07/04: Add stable clues from referential sieve.
2025/07/03: Bob's delaying revokes signal to later players in the reaction.
2025/07/02: Document cleanup
2025/07/02: Remove finesses from trash-reactive targeting priority.
2025/07/01: Added the no good touch principle.
2025/07/01: Remove slot 1 exception for finesses and rules for finessable dupes.