Copyright (c) 2000 Gunnar Kuhlencord, Holzinsel Publ.

This game is played on a 7x7 square board with the following setup:

GOAL BALL - The different color ball placed on the player's corner.
MOVE - On each turn, each player selects a stone. Given a certain direction (up, down, left or right) the move range is given by the number of stones of either color (including itself) placed on the perpendicular direction (e.g., if there are 3 stones on the horizontal, the stone may move 3 cells vertically).
If there are one or more stones (of either color) in the way, they are pushed on the moving direction, and may even be pushed out of the board.
KO rule - It is not allowed to move an opponent's ball back to where it was in the previous move.
GOAL - Wins the player that first places his goal ball at the board center, or pushing the opponent's goal ball out of the board.
An example

White's goal cell cannot move to the center: there are 4 stones horizontally, so the goal cell would pass over the center, landing on d5. 

However, he may move the marked white stone up 4 cells  to cell a5, capturing 2 black stones including the black goal cell, and so winning the game.

For more information check this webpage.