Copyright (c) 1993 Laurent Escoffier

This game is played on a 3x3 square board with the following setup:

TURN -  On each turn, each player must move one of his stacks (i.e., a stack with a friendly top stone).
The moved stack must have one, two or three stones (which means that a stack may be broken in two, moving only the upper part) moving it to an empty cell or on top of another (friendly or enemy) stack.
A moving stack with N stones must move N cells. There are no diagonal moves and stacks can jump over other stacks. 
GOAL - The player that cannot move, loses the game.
An example

White's turn. He has two stacks. The little white stack at a3 can move onto the black stack at c3 (via b3 since jumps are allowed). White could just move the top white stone over the stack at b3, but then Black could reply by moving his new stack at a3 also to b3.

The great white stack at b1 can be used to move one, two or three stones. E.g., White could move one stone to a1, c1 or b2. Also, he could move two stones to a2 (via a1 or b2), to c2 (via c1 or b2) or move over the stack at b3.

Finally, he could move three stones to c3 (by moving b2,c2,c3) or to cells: a1,c1 or a3.

There is a Pogo website with lots of detailed information about the game. It's also possible to download [~350k] a computer opponent (by David Franck).