Copyright (c) 1991 Reiner Knizia, Pro Ligno Spielewerkstatt
This game is played on an empty 7x4 square board:
The green dots show the possible drops of the next player.
|A shift example
Black's turn. If Black shifts the full column, all those stone move one line down and the marked white stone if removed. A new black stone appears at b7.
After the slide, both players will have a 4 in-a-row, so the game continues until at least one of those 4 in-a-rows disappear. Probably, White should shift that column again, since he has a majority of white stones there, and the sequence of shifts will get him a winning position.