Overview

Clobber is an abstract strategy game invented in 2001 by combinatorial game theorists. On a checkerboard-style grid, each square is occupied by either a white or black stone. Players take turns “clobbering” opponent stones by moving their own stones onto adjacent enemy-occupied squares. The player who makes the last legal move wins.

Components

• Rectangular grid board (typically 5x6 or 10x10 for tournament play)
• White stones and black stones (enough to fill every square)

Setup

1. Fill every square on the board with a stone, alternating colors in a checkerboard pattern: white stones on white squares, black stones on black squares.
2. Choose who plays which color. Black typically goes first.

Turn Structure

Players alternate turns. On each turn, a player must make exactly one move.

Actions

Clobber

Pick up one of your stones and move it to an adjacent square (horizontally or vertically, not diagonally) that is occupied by an opponent’s stone. Remove the opponent’s stone and replace it with yours. This is the only type of move in the game.

Scoring / Victory Conditions

The player who makes the last legal move wins. If it is your turn and you cannot make a legal move (none of your stones are adjacent to an opponent’s stone), you lose.

Special Rules & Edge Cases

• Diagonal movement is not allowed; only horizontal and vertical.
• You must clobber an opponent’s stone; you cannot move to an empty square.
• As the game progresses, the number of possible moves decreases as stones are removed.
• The game is a pure combinatorial game with no hidden information or randomness.
• Tournament play typically uses a 10x10 board; casual play uses smaller boards.
• Clobber has been studied extensively in combinatorial game theory.

Player Reference

Legal Move	Move your stone onto an adjacent enemy stone (orthogonal only)
Win Condition	Make the last legal move
Loss Condition	Unable to move on your turn