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# System prepended metadata

title: Sieve Conventions (for 2p Hanabi)
tags: [Hanabi]

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tags: Hanabi
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# Sieve Conventions (for 2p Hanabi)

This document no longer receives updates. Its new home is on the [Hanabi Central Wiki](https://hanabi.wiki/conventions/sieve)


## Introduction
Welcome to the Sieve system for 2-player Hanabi. This convention system tends to significantly outperform traditional discard-oldest strategies. However, major customizations are often required when playing complex variants.

The basic premise of this system is to take the most common discard strategy for Hanabi and flip it on its head. Instead of discarding the oldest unclued card in our hand, we discard our newest card by default. This way, as each card enters our hand, it passes through a sieving process. Either we discard it immediately, or it ends up deeper in our hand where it will be saved indefinitely. When it is not safe to discard from our chop, our partner either gives us a play clue (implicitly saving our chop), or gives us a discard clue that tells us which of our older cards to discard.

Due to the way that discard clues work in this system, finesses/bluffs that involve touching a previously untouched card essentially do not exist. This loss in efficiency is offset by a significant reduction in the number of save clues that players have to give.

### Acknowledgements
Thank you to everyone who helped me playtest this system and extra special thanks to **timotree** and **Lel0uch** for their contributions to early convention development!


## Basic Principles

- **Age Order Principle** - Keep your hand sorted by card age, put newly drawn cards on the left.
- **Chop Principle** - Discard your newest unclued card if you have nothing better to do.
- **Single Focus Principle** - Most clues are focused on a single card, which defaults to the leftmost newly touched card if there is no other obvious focus.
- **Sieve Principle** - Discard modulation comes before most other concerns (let your partner discard trash while it's still on chop!)


## Basic Conventions

Conventions in this section are assumed to be on unless you and your partner explicitly agree to turn them off. They have a proven track record.

### Fill-in Clues
Any clue that fills in a previously clued card as trash or as playable has no extra meaning.

### Rank Discards
Rank clues are discard clues. Discard the unclued card to the right of the leftmost newly touched card.

### Color Plays
Color clues are play clues. Usually the leftmost card is the focus.

### Gentleman's Discards
If you discard a playable card, it promises that card in the oldest possible position in partner's hand.

### Play Priority
It is possible to discard modulate by refusing to play a card that is known to lead to your partner's hand and instead play one that does not. When this happens, your partner should not assume anything extra beyond discard modulation. However, in circumstances where discard modulation is impossible or undesirable, seemingly suboptimal plays should instead suggest that your partner holds the next card in that suit, but may not promise exactly where.


## Advanced Conventions

Conventions in this section are assumed to be on in expert games and off in beginner games unless you and your partner explicitly agree otherwise. They also have a proven track record.

### Zero Clue Safety Promise
Whenever you take any action that will leave the team at zero clues, you promise your partner that they currently hold a safe discard. They are then expected to discard that card next instead of the unpredictable card that they draw from the deck. The exception to this rule is when you retain the ability to communicate about the freshly drawn card (e.g. you will hold two trash cards, or both a playable and promised safe discard). Determining which card is the promised "safe discard" requires using context, but the rough precedence order is: the newest unclued card which is not implied to be good, then the clued card most likely to be non-critical.

### Unlock Promise
When your partner is locked, and pace is >2, it is always better to discard known trash than to play a card that does not immediately unlock your partner. Therefore, if you play a card that looks like it might unlock your partner instead of discarding known trash, you promise that the connecting card is in the oldest possible position in your partner's hand. If there's no possible connecting card, you simply communicate that the oldest possibly playable card is indeed playable.

### Bomb Lock
Misplaying a card that you have permission to discard tells your partner that they are locked. Players should prefer to use this method when possible, so if you choose to use a clue to communicate a lock when you could've safely bombed to do so, you imply that you expect your partner to make a sacrificial discard. Note that you do not generally have permission to discard any card when you have a known playable.


## Example Games

Here are some sample games that demonstrate the conventions. Please feel free to send me additional sample games!

No Variant: https://hanab.live/replay/557894#1
No Variant: https://hanab.live/replay/559047#1
No Variant: https://hanab.live/replay/559287#1
6 suit: https://hanab.live/replay/556956#1
6 suit: https://hanab.live/replay/567595#1
Clue Starved: https://hanab.live/replay/556977#1


## Optional Conventions

Conventions in this section are assumed to be off unless you and your partner explicitly agree to turn them on. Conventions in this section are not necessarily consistent with one another.

### Early Game
If you receive a chop-focus number 2 or 5 clue on the first turn, you do not have permission to discard, and you must stall for at least one turn. Off-chop number 2 or 5 clues allow you to discard chop. The same logic then applies to your clues on the second turn if you weren't given permission to discard.

### Extended Early Game
Before the first discard, an arbitrary number of stall clues are permitted.

### Color Stalls
In stalling situations outside of the first turn (8 clues, locked hand, etc.), off-chop color clues give permission to discard chop, off-chop rank clues have their usual save interpretation. 

### 7-from-8 Stalls
When you are at 7 clues and have no known playable cards on a turn after your partner was at 8 clues, you are permitted to stall.

### Inverted Stall Clues
In stalling situations (8 clues, locked hand, etc.), the meaning of chop-focus save clues is inverted. This means that off-chop save clues still save the card on chop as normal, but "save" clues that focus chop give permission to discard chop (unless the clue itself proves that meaning to be impossible)

### Locked Hand Play Clues
When you have a locked hand and give a play clue to a card that might unlock you, you ask your partner to only play the card when it would result in an unlock and discard as normal otherwise.