Learn SyncChess

Core Rules

1. Simultaneous Moves
   • Both players submit their moves at the same time
   • There are no turns; each round consists of one move per player
2. No Repeating the Same Piece
   • A piece cannot be moved two turns in a row
   • Exception: the king can move multiple times if in check or no other legal moves
3. "Swerving" Rule
   • If you try to capture a piece that moves away, no capture occurs
   • Both pieces simply move to their new destinations
4. Collision Rule
   • If two pieces move to the same square, both are removed

Check & Checkmate

• A king cannot move into a threatened square
• If a king ends up in check from simultaneous moves, that's allowed
• If in check, you must escape on your next move
• If both kings are in check, both must escape next turn
• Checkmate wins immediately, even if you're also in check
• Simultaneous checkmate results in a draw

Special Moves

• Castling: Works as normal but simultaneously. The king moves two squares towards the rook, and the rook "jumps" over.
• En Passant: If a pawn moves two squares forward, an enemy pawn can capture it as if it moved only one square.
• Pawn Promotion: When a pawn reaches the opposite end, it can be promoted to any piece except a king.
• King's Extra Move: Kings can move twice in a row when in check to escape danger.

Timer System

• Each player starts with their selected time
• Both timers run while deciding moves
• Timer stops when you submit your move
• If one player submits first, only the other's timer continues
• Running out of time loses the game