Copyright (c) 2003 Joćo Neto

The game starts at following hexagonal board (the central stone is called the neutral stone). There are also enough one color stones off board.

GROUP - One or more connected stones of the same color.
EDGES - Each player owns three non adjacent board edges. Let's denote North (South) the player which owns the north (south) edge.
MOVE - On each turn, a player drops one stone on an empty cell, provided:
The dropped stone becomes part of a group of N >=1 stones where at least one of its stones is in a line of sight with the neutral stone, with at least N empty cells beyond it.
Then, the neutral stone moves N cells away from the stone mentioned (the player may choose, if there is more than one direction)
GOAL - A player who cannot make a legal move on his turn loses, otherwise a player wins if the stone reaches one of his edges.
If the stone reaches a corner, the player that just moved wins.
An example

If the player drops at the green cell he wins the game by moving the neutral stone to one of his edges (assuming that the player owns that edge). 

That dropped stone will belong to a group of 4 stones, and so, the player may push the neutral stone four cells west, away from one of the group stones.

Instead, he cannot drop at the red cells, because in that case, the neutral stone would need to slide exactly 5 cells and there is not enough space to do that.

Stalemating the adversary

South dropped the marked stone, stalemating North and winning.

Winning a fast game

North dropped the marked stone and wins the game(!). South cannot do anything to stop the neutral ball reaching the SW edge.

A winning path

South drops the marked stone. Now all the next moves, moving the neutral ball from [1] to [4] are the only possible ones (can you find where the players must drop their stones), giving a victory to South!!

The last 3 examples where taken from actual games.