Rules of XYMYX·Chess
It’s chess, but both players move at the same time. Everything else is the same, except for these rules.
Ordered like the app tutorial: first what you’ve already practised, then what you still need to play well.
Tutorial level 1
The basics
Each level plays on its own, like the app tutorial. You can pause it, go step by step or change the speed.
Level 1, step by step
1Queen placement
There is no white or black: both queens start to the left of their king.
2Simultaneity
Each player picks a move in secret. Both moves are played at the same time.
See details
Once you lock in your move you can’t change it, and your clock stops. When both players have locked in, the moves are played and the clocks start again.
3Failed capture
If the piece you want to capture moves on that same turn, the capture doesn’t happen.
See details
This applies to pawns too: if the pawn you wanted to capture advances at the same time, your pawn captures nothing.
4Collision
If two pieces land on the same empty square, the higher-ranked piece stays.
See details
If both pieces are the same, the piece of the player who locked in first stays.
Tutorial level 2
Frozen pieces
Level 2, step by step
5Queen and Rook freeze
If the Queen or the Rook gives check, it becomes frozen and can’t move on the next turn.
Tutorial level 3
Absorption
Level 3, step by step
6Simple absorption
You can capture one of your own pieces, except the king. The piece that moved stays.
7Double absorption
If you absorb one of your pieces and your opponent moves onto that square at the same time, your moving piece wins.
See details
Three pieces meet on one square: two of yours and one of your opponent’s. Your opponent’s piece and your piece that was already there leave the board. Use it to anticipate and protect key pieces.
What the tutorial doesn’t teach
Essential to play
Two ideas that change everything compared with classic chess. Each example plays on its own, at reading pace. You can pause it, go step by step or change the speed.
8There are no pinned pieces
You can move a piece that shields your king. The king is never captured: at most, it ends up in check.
Variant: the bishop moves too
While you move your knight, the threatening bishop may move to another square. Then the check never even happens.
9AKing defence: normal check
If you’re checked by a piece that doesn’t freeze (Bishop, Knight or Pawn), the only defence is to move the king.
10BKing defence: frozen piece
If the check comes from a frozen Queen or Rook, you have three defences: capture it, block the check or move the king.
Option 1: capture the frozen piece
Option 2: block the check
Option 3: move the king
Summary: who is checking you?
Only one defence: move the king to a safe square.
Three defences: capture, block or move the king.
For reference
Rare cases
They rarely happen. Open them when a question comes up during a game.
Castling
You can’t castle if the king or the castling rook is under attack at that moment.
Simultaneous checks
- If both players are in check, both must move their king to a safe square.
- If one gives check and the other gives checkmate, the checkmate wins.
- If both give checkmate, whoever locked in their move first wins.
Pawn promotion
A pawn that reaches the last rank instantly becomes the piece you choose. If an opponent’s piece moves onto that square at the same time, the collision is resolved with the new piece: the higher-ranked piece wins and, if they are equal, the piece of the player who locked in first.
En passant
It doesn’t exist in XYMYX.
Pawn collisions
Pawns only capture diagonally. If two pawns advance straight onto the same empty square, the pawn of the player who locked in first stays. If your king and an opponent’s pawn advancing straight reach the same square, the king stays: that pawn wasn’t threatening it.
The two moments of a turn
Every move is decided by looking at the board before moving. Whatever happens after both moves are played is the consequence, and it doesn’t change whether your move was legal. A XYMYX turn contains two moves: yours and your opponent’s.