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What is Pie Chess?

Pie Chess is a new chess variant in which one player sets up a custom position, and the other player decides which colour to play or to take draw odds.

The name "Pie Chess" is an allusion to the pie rule, where someone cuts a pie into two slices and lets the other person choose which slice they want, incentivizing cutting it fairly. This rule is used in other games such as Hex to make the first move more fair. Similarly, in Pie Chess, the player who sets up the position must create a balanced position, knowing that their opponent will get to choose the more advantageous side.

How It Works

  1. Edit distance protocol (default for new games):
    • A coin flip picks who proposes the maximum plies from the standard start (0–200).
    • The other player chooses who creates the position by playing legal moves (not importing a FEN).
    • Whoever did not create the position chooses Win (with a colour) or Draw odds.
  2. Legacy mode (optional): one player sets up a custom position freely; the other chooses Win/Draw as before.
  3. Draw odds: The player who did not choose Win gets draw odds (they win if the game is drawn).
  4. Gameplay: Normal chess with clocks after the choice phase; Player 2 receives a time bonus for deliberation.

See this article for the edit distance protocol.

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📊 ELO Rating System

Pie Chess uses a Maximum Likelihood ELO rating system to calculate player rankings. Your rating starts at 1500 (the default beginning rating) if you have no games played.

How it works: The system uses Bayesian inference to determine optimal rating ranges that best explain the observed match outcomes. Instead of giving a single point estimate, the system calculates rating ranges that reflect confidence based on available data:

  • Narrower ranges indicate more confidence (more comparison data)
  • Wider ranges indicate more uncertainty (less comparison data)
  • Ratings are calculated using the standard ELO formula: P(x beats y) = 1 / (1 + 10^((y - x) / 400))

Note on Cheating Detection: While we are not currently implementing automated cheating detection, we monitor game patterns and may investigate suspicious activity. Fair play is essential for maintaining accurate ratings.

Tournaments: In tournament mode, all players' ratings are reset to 1500 at the start. Ratings are then calculated after a set number of games that participants play.

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