FocusRules

Focus is a checkers variant invented in 1963 by Sid Sackson.

Number of players: 2

Equipment: An 8×8 board; 18 checkers in each of two contrasting colors

Setup

Arrange the checkers in the center of the board like this. The three squares in each corner are ignored.

A stack comprises between one and five checkers. Ownership is determined by the checker on top of a stack. The stack size is equal to the number of checkers it comprises.

Play

Before the first turn, both players switch two or more checkers to achieve an asymmetric board, to avoid an easy draw for the second player.

On his proper turn, each player must do one of the following:

1. Move one of his stacks horizontally or vertically, a number of cells equal to its size. It may land on another stack. A move may be made only with an upper part of the stack. That sub-stack moves the number of cells equal to its own size. Capture: If, after landing, the final stack size exceeds 5, all excess checkers are removed from the bottom of the stack. Enemy checkers are removed, and friendly checkers are added to the player’s reserve.
2. Use one of his reserve checkers and place it on any cell, occupied or not. If the target cell is occupied, the checker is placed on top of the stack. Any excess beyond five checkers must be removed from the board.

Winning: You win if your opponent cannot make a valid move.

Sample Game

It is Black’s move. Black has four reserve checkers, and White has two. Black’s position is better.

Black can play a reserve checker at b6, taking that stack. White can attack f2 by moving g3-g2 (f2 cannot move to g2). But Black can reply with b6-f6, protecting his stack on f2.

Source: http://www.di.fc.ul.pt/~jpn/gv/focus.htm